B.A.R.C.-1458

SBO

DIVISION OF RADIOLOGICAL PROTECTIONPROGRESS REPORT

1982 - 1988

Edited by

B. L. Gupta, R. M. Bhat and G. R. Narayan

1989

B.A.R.C. -

GOVERNMENT OF INDIAATOMIC ENERGY COMMISSION

CJ

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DIVISION OF RADIOLOGICAL PROTECTIONPROGRESS REPORT

1982 - 1988Edited by

B.L.. Gupta, R.M. Bhnt ;ind G.R. N;irny;iri

BHABHA ATOMIC RESEARCH CLNTRLBOMBAY, INDIA

1989

B.A.R.C. - 14!>8

INKS Subject Category : C55.OO; C54.00

Descriptors

RADIATION PROTECTION

INDIA

PROGRESS REPORT

PERSONNEL MONITORING

DOSIMETRY

DOSEMETERS

CALIBRATION STANDARDS

RADIO1SOTOPES

RADIATION MONITORS

MEDICAL SURVEILLANCE

NUCLEAR MEDICINE

EDUCATION

ABSTRACT

This report describes the work of the Division of Radiological

Protection during 1982-88, for implementation of radiation safety in

all institutions in the country using radiation sources for medical,

industrial and research applications. It gives information about

personnel monitoring using photographic film and TLD badges, neutron

monitoring badges, dosimetric techniques developed, calibration

facilities and maintenance of national standards for radiation and

radioactivity, design and fabrication of special radiation protection

instruments, development of coloured indicators for identification of

radiation sterilized medical products, advisory and licencing

services, regulation and transport of radioactive materials, periodic

protection survey, education and training related to radiation safety

programmes. About 500 publications by the staff of thia Division are

listed.

FOREWORD

The Division of Radiological Protection (DRP) is responsiblefor the implementation of radiation safety in all inatitutionis inthe country using radiation and radioisotopes for medical,industrial, agriculture and research applications. The Divisionis organised into six sections consisting of 36 groups in orderto fulfill this objective. Services extended by the Division aremandatory requirements under the Radiation Protection Rules 1971.Close liason is maintained between DRP and the Atomic EnergyRegulatory Board, the competent authority under the Rules in allradiation safety enforcement policies.

One of the important functions of DRP is to providepersonnel monitoring services to all radiation workers in thecountry. A total of about 33,000 radiation workers in 2780institutions are monitored at present. Recently, a number of•institutions specially all DAE units have been provided with TLDbadges for personnel monitoring. These TLD badges including theteflon embedded CaSCU :Dy discs used in the cards are gotfabricated locally and supplied by the Division. The serviceUnits are also located at Calcutta, Kalpakkam, Tarapur, Kota,Narora and Hyderabad.

At present, there are 155 teletherapy units, 10 medicallinear accelerators, 60 brachytherapy facilities for cancertreatment, 86 nuclear medicine centres mostly for diagnosticpurposes and 330 research institutions using radioisotopes. Inaddition, there are 1100 industrial radiography cameras, 1900nucleonic gauges in use and 200 tons of thorium per annum is usedin the gas mantle industry. There are about 70 gamma irradiationchambers and several high dose irradiation facilities* Advisoryservices and licensing activities connected with all radiationequipment as well as radioisotopes including their planning havebeen carried out effectively. In order to ensure adequateradiation safety, periodic protection surveys are performed andwherever required assistance has been given for handlingemergency situations involving radiation sources. A detailedemergency response plan for dealing with transport accidents hasbeen prepared in consultation with various concerned agencies.This Division has been responsible for working out proceduresfor the safe transport of radioactive materials and implementingthem.

The Division maintains a number of national standards forradiation and radioactivity and calibrates dosimeters, radiationmonitors and radiation sources. It provides a centre forcoordinating radiation measurements at different laboratories inthe country and ensures the traceability of these measurements tonational primary standards and also provides a link withinternational standards organisations such as BIPM, IAEA and ICRM.

The Division has an active programme for designing andfabricating special radiation protection instruments required formonitoring purposes. In addition, personnel monitoring badgereaders based on TLD as well as film, are fabricated by thisDivision itself. Secondary standard dosemeters, thermolumine-scent dosemeters, clinical dosemeters etc. are fabricated andsupplied by this Division to meet the requirement of variousradiotherapy centres in the country. Coloured indicators foridentification of radiation sterilized medical products arebeing prepared and supplied to more than 100 establishments usingISOMED and RASHMI facilities at Bombay and Bangalorerespectively.

The Division gives considerable importance to impart propertraining and prepare the necessary manpower required forimplementing the countrywide radiation safety programme. Forthis purpose a number of long and short term training courses arebeing conducted.

Various sections are also actively engaged in relevantresearch and development work in order to give support to theaims and objectives of the Division. Radiation Biophysics Groupis engaged in radiobiological research aimed at understanding themodification of radiation effects by chemical and physical agentsat cellular and micromolecular level. Interaction of radiationand chemical radiosensitizers or ozone at molecular level arealso studied. Computational studies cover areas of dosimetry ingeneral, radiation transport in shields, detector response toneutrons etc.

The work of this Division has been presented in the form ofvarious brochures and publications in reputed journals. Thevariety and depth of the various topics on research anddevelopment undertaken by DRP has been presented in this report.A list of about 500 publications by the staff of this Division isalso given along with the work of each s«cticm.

(U. Madhvanath)Head

Division of Radiological Protection

C O N T E N ..T „§.

Page_.No....

A. RADIATION BIOPHYSICS AND DOSIMBTRY SECTION

1. Chemical dosimetry 12. Radiation biophysics 73. Dose modifier studies 184. Theoretical studies 21

B. -RADIATION METROLOGY SECTION

1. Radionuclide standards 262. Neutron standards 363. Standards for photon beams 424. Calibration of radiation instruments 485. Services 53

C. PERSONNEL MONITORING AND RESEARCH SECTION

1. Personnel monitoring service 592. Neutron monitoring 633. TLD personnel monitoring service 644. Dose records and statistics 705. Personnel monitoring and TLD development works 716. Population exposure studies 77

D. RADIATION PROTECTION INSTRUMENTATION SECTION

1. Radiation protection instruments 962. Radiation dosimeters 1123. Personnel monitoring instruments 1244. Miscellaneous 131

B. MEDICAL PHYSICS AND SURVEILLANCE CELL

1. Service activities 1432. Nuclear medicine advisory services 145

F. INDUSTRIAL ADVISORY AND CONTROL SECTION

1. Services rendered 1522. Internal monitoring of workers 153

handling radioluminous paint

G. TRANSPORT ADVISORY SERVICES 158

H. EDUCATION AND TRAINING 161

I. LIST OF PUBLICATIONS - 1988 163

Report typed by : Shri V.K. Kandalkar

: 1 :

A. RADIATION BIOPHYSICS AND DOSIMETRY SECTION

1. Chemical Dosimetry

1.1 Free radical dosimetry

B.L. Gupta, R.M. Bhat, G.R. Narayan and S.R. Nilekani

An accurate, simple, convenient and inexpensivespectrophotometric method for free radical dosimetry wasdeveloped under IAEA research contract. The method is based onthe oxidation of ferrous ions by stable free radicals formed inirradiated alanine/glutamine powder when it is dissolved in asolution containing ferrous ammonium sulphate and xylenol orangein 0.05N sulphuric acid (FX). Ferric ions thus formed form acomplex with xylenol orange and its absorbance is measuredspectrophotometrically. This technique has a reproducibilitybetter than t 2%. It offers an alternative to ESR andlyoluminescence methods for free radical dosimetry.

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Dose intercomparison studies were carried out using thistechnique by sending alanine and glutamine dosimeters toInstitute of Isotopes (INISO), Budapest and ISOMED, BARC forgamma irradiations and to RISO, Denmark for gamma and 10 MeVelectron irradiations. For gamma irradiations, alanine dosimetergave an agreement within ± 3% above a dose of 1 kGy(Fig.l), whileglutamine dosimeter gave an agreement within ±3% at all doselevels (Fig.2). For 10 MeV electron irradiations similaragreement was obtained above 10 kGy dose. Dose intercomparisonfor 400 - 500 keV electrons using FWT-60 film and glutaminedosimeter was also carried out in collaboration with RISO,Denmark and ARC, Vienna. Both techniques showed a good agreement.

Dose assurance programme was initiated for the benefit ofthe users of high dose radiation facilities in our country, usingalanine/glutamine dosimeters. Initially, seven institutions w«recovered under this programme. The difference in the measureddose and nominal dose was found to vary from 1.7 to 50%. Themain reason for large variations was that the dose rate variationwithin the irradiation volume of gamma chamber was not taken intoconsideration by the users. Secondly, some persons used thecalibration values given to them long back by the gamma chambermanufacturers, without any recalibration.

1 • 2 Visual monitoring system for personnel in..«.. nuc.le.axemergency

B.L. Gupta, R.M. Bhat and G.R. Narayan

During a nuclear emergency, the number of personnelexposed to radiation may be very high. A quick assessment ofdose received by individuals is very essential for immediatemedical management. A visual indicator in liquid form usingferrous sulphate, benzoic acid and xylenol orange in sulphuricacid is developed for this purpose. A filter strip cotainingJtylenol orange is added to the colourless solutions and thedistinct colour changes at different dose levels indicate thedose received by the individual. Actual dose can also bemeasured with a spectrophotometer. This system has a preirradiation stability of atleast one year.

Table 1 . Colour changes at different dose levels

Dose (Gy) Colour

0 Yellow0.5 - 2.0 Light brown2.0 - 4.0 Light pink

> 4.0 Violet

3 :

1. 3 indicators_f or i.rradiation verification

B.L. Gupta, S.R. Nilekani and B. Suseela

Radiation sterilization of medical products requires adose of 25 kGy. To differentiate the irradiated product from anunirradiated one, an indicator which undergoes a change in colouron irradiation has been developed. This is an emulsion of PVCcontaining a pH sensitive dye. Those indicators change colourfrom yellow to red on irradiation. Various difficulties inmaking the indicators on large scale have been overcome.Indicators are now being supplied to different companies usingISOMED facility in BARC. Table 2 below shows the number of usersand indicators sold since 1982.

Table 2. Status of indicator used during the past 6 years

Year No. of users Indicators sold (lakh)

1982198319841985198619871988

102436527490108

1.482.946.446.7111 .1013.6415.54

1•4 Workshops on calibration of high dose radiation facilities

B.L. Gupta, U.R. Kini, R.M. Bhat, G.R. Narayan,Rm.S. Ramaswamy, S.R. Nilekani and B. Suseela

Two workshops were organised for the users of highintensity radiation sources, first in October 1983 and second inMay 1986. About 40 participants from various institutions inIndia were benefited by the workshops. It covered lectures onvarious topics like interaction of radiation with matter,elementary radiation chemistry, radiation processing, highintensity radiation sources, dose distribution, fundamentals ofdosimetry, various dosimeters and their applications. Practicalson dosimetry were also conducted. A BARC report No. 1303 titled"Calibration of high dose radiation facilities (Hand book)" wasbrought out during the workshop.

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1.5 FBX dosimeter

B.L. Gupta, U.R. Kini, R.M. Bhat, G.R. Narayanand Rm.S. Ramaswamy

The FBX system has been found to be very useful inradiation dosimetry. It contains 0.20 mM ferrous ammoniumsulphate, 5.0 mM benzoic acid and 0.20 mM xylenol orange in 0.05N Hz SO* . In this dosimeter, the absorbance is measured at 540nm. However, the acid concentration i:or optimal complexformation and the absorption peak of the complex may slightlychange due to the presence of some impurities in xylenol orange.Therefore, the optimal acid concentration is used in thepreparation of FBX dosimeter for the xylenol orange used and themolar abosrption coefficient is measured at the proper absorptionpeak. Under these conditions, the calibration curve for FBXdosimeter prepared by using xylenol orange obtained fromdifferent manufacturers is reproducible within an accuracy of ±0.6%. Therefore, this system can be used as a primary standardfor dose calibrations. Though the response of the systemincreases with the increase in oxygen concentration in thesolution, the normal aerated solutions give more reproducibleresults. The following relationship is used for the dosecalculations:

(1/ffe3* )) = (0.179/Dose) + 0.003where [Fe3t] is expressed in micromoies/litre and dose in Gray .

The FBX system has been used to measure central axis depthdose for both photon and electron beams. Unlike the ionizationchamber measurements, the FBX dosimeter in water phantom givesabsorbed dose directly and requires no corrections. Thisdosimeter has been tested for field use. A portable filtercolorimeter has been used for this purpose and found to besatisfactory.

Depth dose data measured by FBX showed significantvariation from the BJR-17 values. The variation depends on thefield size also. The ionization chamber shows about 2% lessresponse at 20 cm depth as compared to the FBX dosimeter. Thedeviation seems to be due to scatter contribution from themachine as ionization chamber shows lesser response to theseradiations compared to the FBX dosimeter.

The FBX dosimeter containing 0.1 mM ferrous ammoniumsulphate, 1.0 mM beazoic acid and 0.05 mM xylenol orange in 0.08N HzSO« has better pre and post irradiation stability. However,the composition has to be carefully controlled for good accuracy.This composition can be used for postal dosimetry and other useswhere longer post-irradiation storage is required.

PUBLICATIONS

1. Free radical dosimetry by chemical read out, B.L. Gupta, R.M.Bhat, G.R.Narayan and S.R. Nilekani, Proc. of 5th Tihanysymposium on Radiation Chemistry, Siofok, Hungary, Sept.(1982) 703.

2. Use of the FBX dosimeter for the calibration of cobalt-60 andhigh energy teletherapy machines, B.L. Gupta, U.R. Kini, R.M.Bhat and U. Madhvanath, Phys. Med. Biol. 27 (1982) 285.

3. Effect of post irradiation storage in eerie sulphatedosimeter, B.L. Gupta, Rm.S. Ramaswamy and R.M. Bhat, Proc.of DAE Symp. on Radiochemistry and Radiation Chemistry,University of Poona, Dec. (1982), Paper No. RD-12.

4. Acid and xylenol orange effects in the FBX dosimeter, B.L.Gupta, R.M. Bhat, G.R. Narayan and B. Suseela, Int. J. Appl.Radiat. Isot. 34(6) (1983) 887.

5. A hand book on calibration of high dose radiation facilities,B. L. Gupta and R.M. Bhat, BARC/DRP/TC-4 (1983).

6. interface effects in dosimetry by different types ofdetectors, B.L. Gupta and U. Madhvanath, Bull. Radiat. Prot.7 (1), (1984) 3.

7. G ( f o D t l values in the FBX dosimeter, B.L. Gupta and G.R.Narayan, Phys. Med. Biol. 30 (1985) 337.

8. A spectrophotometric readout method for free radicaldosimetry, B.L. Gupta, R.M. Bhat, G.R. Narayan and S.R.Nilekani, Radiat. Phys. Chem. 26 (6) (1985) 647.

9. A new technique for dosimetry of low energy electrons, B.L.Gupta and S.R. Nilekani, Bull. Radiat. Prot. 8(1) (1985) 29.

10. Oxidation of ferrous ions by irradiated solid amino acids,Radiochemistry and Radiation Chemistry Symp., IIT, Kanpur(1985) 296.

11. Radiation chemistry of xylenol orange in aqueous solutions,Radiochemistry and Radiation Chemistry Symp., IIT, Kanpur(1985), 299.

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12. G(Fe3M values in FBX dosimeter at low dose rates, B.li.Guptaand U. Madhvanath, Int. J. Appl. Radiat. Isot. 36 (12) (1985)985.

13. Mechanism for the radiolytic conversion of sulphur dioxideto sulphuric acid, B.L. Gupta and B. Suseela, Radiation Phys.and Chem. 27 (2) (1986) 75.

14. Calibration of high dose radiation facilities, B.L. Gupta andR.M. Bhat, BAP.C report No. 1303 (1986).

15. Intercomparison of ionisation and chemical dosimetrictechniques for central axis depth dose measurements fromteletherapy machines, B.L. Gupta, U.R. Kini, R.M. Bhat and U.Madhvanath, Asian Regional Conference on Medical Physics,BARC, Dec. (1986) 28.

16. Dose intercomparison using spectrophotometric read out methodfor free radical dosimetry, B.L. Gupta, R.M. Bhat, G.R.Narayan, S.R. Nilekani, N.G.S. Gopal and A. Kovac's,Znt. J.Appl. Radiat. Isot. 37 (1986) 127.

17. Dose intercomparison for 400-500 keV electrons using FWT-60films and Glutamine (Spectrophotometric readout) dosimeters,B.L. Gupta, S.R. Nilekani, P. Gehringer and A. Miller, Appl.Radiat. Isot. 37 (9) (1986) 965.

18. Visual monitoring system for personnel in a nuclearemergency, R.M. Bhat, G.R. Narayan and B.L. Gupta, Bull.Radiat. Prot. 10 (1-2), (1987) 21.

19. Stable FBX system for postal dosimetry of teletherapymachines, B.L. Gupta, R.M. Bhat and G.R. Narayan, AMPI Med.Phys. Bull., Paper IV/5, 12 (4) (1987)6.

20. Effect of impurities in xylenol orange on the response of FBXsystem, B.L. Gupta, R.M. Bhat, G.R. Narayan and Rm.S.Ramaswamy, AMPI Med. Phys. Bull, paper V/22 12 (4) (1987) 27.

21. The effect of oxygen concentration on benzoic acid sensitizedradiolytic chain oxidation of ferrous ions, Rm.S. Ramaswamy,R.M. Bhat, G.R. Narayan and B.L. Gupta, ISRAPS Seminar onRadiation and Photochemical Sciences, IIT, Bombay, Dec.(1987) 38. (Abstract).

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2 .1 Influence._.of heat treatment on the .recovery, fromrA4ijLt_ion__damacfe in. yeast

B.S. Rao, K.B. Anjaria and V.V. Deorukhakar

Recovery from radiation damage was studied in diploidyeast Saccharomyces cerevisiae BZ 34 subjected to pre, post orsimultaneous hypertnermic treatment. Pre-irradiation heattreatment at 51°C for 20 min sensitized the cells to lethaldamage, however these cells could efficiently recover frompotentially lethal damage (PLD) on liquid holding. On the otherhand post-irradiation hyperthermia (51°C-20 min) almostcompletely inhibited recovery from PLD and significant inhibitionwas seen even for 49°C-60 min treatment. For treatments at 40°Cand 45°C the inhibition of recovery was restricted to theduration of heat treatment. As soon as these cells weretransferred to 30° C they could show significant recovery fromPLD. When both heat and radiation treatments were simultaneouslydone by irradiating the cells at 48°C, PLDR inhibition waspartial. The recovery factor calculated as the ratio of survivalafter recovery, to that upon immediate plating (without PLDR),2.6 ± 0.9 for simultaneous heat and radiation treatment ascompared to 11.9 ± 2.7 observed for radiation alone. Cellsirradiated, allowed to recover from PLD for 48 hours and thensubjected to heat treatment at 51°C for 20 min were unaffected byheat treatment suggesting that sensitization occurs only whenheating is done immediately after irradiation. Post irradiationincubation of cells at 37°C showed a considerable reduction insurvival as compared to cells at 30° C for 300 Cy and 600 Gy m;i"«0.34 and 0.12 respectively, suggesting the inhibition ofsublethal damage repair upon incubation at supra-optimaltemperature.

2.2 Modification of radiation induced damage byhypertliermia - role of repair processes

V.V. Deorukhakar and B.S. Rao

Role of repair inhibition in hyperthermic sensitizationhas been investigated by carrying out interaction studies (nonlethal heat + radiation) using three radiosensitive mutantstrains rad 9-4, rad 51 rad 52 of diploid yeast. Theradiosensitij.ation observed in these mutants was compared with

t 8 :

that obtained with a wild type strain X 2180. Stationary phase;cells were heat treated at 51°C for 30 min and log phase cells at49°C for 5 min such that the heat treatment per se was nonlethal. Thermal enhancement ratios (TER) were calculated as theratio of Do values as well as Di o values observed for radiationalone to that obtained for combination of heat and radiation. Instationary phase cells TER values ranged from 1.35 - 2 indifferent strains. There was no significant difference in thedegree of sensitization in wild type and mutant strains. Howeverin log phase cells TER calculated as the ratio of Dto values was1.84 for wild type strain; whereas the same was 1.20, 1.21 and1.50 for rad 9-4, rad 51 and rad 52 strains. TER values obtainedfrom ratio of Dg values however wore not significantly differentfor wild type and mutant cells oven i n log phase cultures. Thust;results suggest that the radiosensi t i zaVIon by heat: occmsprominantly in radio-resistant log phase cells and reflects as areduction in the shoulder width of survival response cuivt's.Even in haploid yeast strains which do not show an initialshoulder TER value is only 1.11 as compared to 1.73 in wild » ypfstrain. Inhibition of recovery from sublethal damage by heatappears to be an important cause of radiosensitization.

2 . 3 Mod ifi.cat i.on_o_f_ _ a.d_i_a_tiqn. inducedgene conyersion inyeast by hyperthermia

K.B. Anjaria and B.S. Rao

It has been observed that hyperthermia induces cellkilling and it also sensitizes cells towards radiatior inducedlethality. On the basis of these observations, hyperthermia isused either alone or in combination with radiation for thetreatment of cancer. Although number of studies have describedthe sensitizing effects of hyperthermia for radiation inducedcell killing, very little is known about the effect ofhyperthermia on the genetic events induced by radiation.Stationary phase cells of diploid yeast SaccharomycescerevisiaeBZ 34 were subjected to non-lethal as well as lethal hyperthermictreatment either before or after irradiation. Hyperthermictreatment was carried out at 51°C for 20 min (100% survival) orfor 40 min (50% survival). ,nma irradiation was carried out ina Cobalt-60 gamma chamber having a dose rate of 40 Gy/min.Radiation exposures were in the non-lethal dose-range of 20-100Gy. Our results indicated that pre-heat treatment enhanced CM mmaradiation induced gene conversion frequency. The increaseabout 25% for non-lethal heat treatment and 65% for lethal heat

: 9 *

treatment. Post irradiated non-lethal as well as lethal hyattreatment had no effect on radiation induced gene conversionfrequency.

2 . 4 Int_erac_t_ion_. js.tud.iej3... between radiation and various chemical§3.§.D_ts__i.9X..JLhJl_indu.ct.ion....of...£[eneti_c damage

K.B. Anjaria and U. Madhvanath

An understanding of the possible modes of interactionnamely, additivity, synergism, or antagonism has relevance inradiation protection. Standard chemical mutagens-Ethyl methanesulphonate (EMS), Methyl methane sulphonate (MMS) and 4-Nitroquinoline 1-oxide (4-NQO) were used in combination withgamma radiation in the non-lethal dose range. When a chemicalmutagen interacts with radiation at the sub-lethal level, anadditive response is most likely to be observed. The twoalkylating agents EMS and MMS showed an additive interactionwhereas 4-NQO showed an antagonistic interaction with gammaradiation indicating that mutagenic interaction at sub-lethallevel may also result in less than additive response. Sodiumselenite, a chemical of industrial importance and also anantimutagenic/anticarcenogenic agent exhibited genotoxic effectsby itself. In interaction studies with radiation or MMS, it wasobserved that selenite at non-mutagenic concentrations did notmodify radiation or MMS induced gene conversion frequency. Atmutagenic concentrations, selenite exhibited additive orsynergistic interaction. The tumour promoting agent iodoaceticacid, when used at non-toxic doses had no effect on radiationinduced gene conversion frequency.

2•5 Interaction between cigarette smoke condensate andr_ajy.j.t.ipnj_pjr.._t e_ind.u.cjtj._on.._o_f genotoxic effect in yeast

N. Sankaranarayanan and B.S. Rao

Genotoxic activity of cigarette smoke has beenestablished. Interaction between gamma radiation and cigarettesmoke condensate (CSC) in the induction of gene conversion in twostrains of diploid yeast Saccharomyces cerevisiae D7 and B2 34was studied. Additionally, how the genotoxic effects of CSCvary with different strains, cell stage, treatment conditionssuch as concentra- tion, duration of treatment etc. have alsobeen studied. In both D7 and BZ 34 strains, the interactionbetween CSC and gamma radiation produced an additive effect. Thereversal of the order of treatment had no effect on combined

: 10 :

response in terms of cell survival or induction of geneconversion. It was observed that on treatment with CSC theconversion frequency increases with time and reaches a plateau.The log phase cells were found to be more sensitive to killingand induction of gene conversion. Interaction between CSC andradiation was additive even in log phase cells. Both BZ 34 andD7 showed qualitatively smilar response to induction of mitoticgene conversion as well as cell killing. At a given level ofcell survival CSC was found to be very weakly mutagenic ascompared to gamma radiation.

2.6 Effect of caffeine on the gamma radiation induced geneconversion and back mutation in yeas t

B.S. Rao, N. Sankaranarayanan and K.B. Anjaria

Caffeine is known to interfere with post-irradiationrepair processes in bacteria, yeast and mutation cell systems.The effect of caffeine on the radiation induced geneticevents indiploid yeast strains Saccharomyces cerevisiae BZ 34 and D7 wasstudied. Stationary phase cells irradiated to non-lethal andlethal doses of gamma radiation were plated on media containing0.01, 0.03 and 0.1% W/V caffeine, and also on media which did notcontain caffeine. The results obtained with BZ 34 strainsindicated that radiation induced gene conversion frequency wasreduced significantly in the presence of caffeine. Decrease inthe conversion frequency was significant (40-60%) in cellsexposed to lethal radiation doses and for cells plated in thepresence of high concentration (0.1% W/V) of caffeine. Similarresults were observed with D7 strain. It was observed thntcaffeine at 0.1% W/V concentration reduced the radiation inducedcell killing as well as the frequency of gene conversion, backmutation and the percentage of aberrant colonies. This effectwas not seen for non lethal radiation dose but was marked forlethal radiation dose of 60 krad. The percent survival increasedby 50% whereas the gene conversion and back mutation frequencydecreased by 50% and the frequency of aberrant colony formationdecreased by 20%.

2.7. Effect of cycloheximide on the expression of geneconversion in yeast induced by N-Methyl-N'Nitrp-W-Nitrosoquanidine and gamma radiation

M.S.S. Murthy

Treatment of cells with protein synthesis inhibitors

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subsequent to exposure to PNA damaging agents has been a standardprotocol to investigate the need for fresh protein synthesis inthe repair of DNA damage. Cycloheximide (CH) is a potentprotein synthesis inhibitor. N-Methyl-N'-nitrosoquanidine (MNNG)and gamma radiation produce various types of DNA damage in yeast.Some of these may lead to gene conversion by recombinationpathway.

Diploid yeast cells teated with graded doses of MNNG orgamma radiation were divided into two parts. One was platedimmediately to determine the frequency of gene conversion inducedby the treatment. The other was incubated in CH before platingto examine the effect of protein synthesis inhibtion on theinduction of gene conversion. Experiments were done with bothstationary and log-phase cells. Results showed that proteinsynthesis inhibition by CH had no effect on the induction of geneconversion by MNNG and gamma radiation. This may suggest thatrecombination pathway may be constitutive in this system.However, alternative explanations were plausible. A properinterpretation of these results require information on the fateof the pre-recombinational lesions in the presence of CH.

2.8 Influence of anoxia on the qenotoxicity of some mutagenicchemicals in yeast

V.V. Deorukhakar and M.S.S. Murthy

Influence of anoxia on the cytotoxic and recombi.iogeniceffects of four mutagenic chemicals, 4-nitroquinoline-o-oxide(4-NQO) N-methyl-N -nitro-N-nitrosoouanidine (MNNG), methylni-trosourea (MNU), and methylmethanesulfonate (MMS) in yeast hasbeen studied. Anoxia enhanced the effects of 4 NQO. This isexplained on the basis of the need for reductive metabolism by 4NQO to generate cytoxic and genotoxic intermediates. Anoxia hadno influence on the effects of MMS. On the other hand itsignificantly reduced the effects of both MNNG and MNU. This wasunexpected. Both MNNG and MNU dissociate to form methylatingspecies which bind to DNA leading to cell killing and geneconversion. There was no difference in the rate of degradationof these agents under aerated and anoxic conditions. Hence theobserved influence of anoxia is probably due to some crliularparameters which are the consequences of anoxia. A clearundersanding of the influence of anoxia on the effects ofcytotoxic chemicals is essential in designing drugs for thetreatment of solid tumours which are known to contain hypoxiccells.

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2.9 Failure of exogenous methylated adenine to inducecytotoxic and geneotoxic effects i.n__Y_eaLst_auxotrophicto adenine

M.S.S.Murthy and V.V. Deorukhakar

Alkylation of DNA is an important step in the biologicaleffects of alkylating agents. In an attempt to determine theeffect of alkylation at Ni and N» positions in adenine, diploidyeast auxotrophic to adenine was cultured in synthetic medium inWhich adenine was replaced by Ni or Na methylad«?niner-. Theexpectation was that, the cells will incorporate methy'ladeninesto the DNA freshly synthesised by the salvage pathway and thusfacilitate the expression of their biological effects, if any.The biological end points monitored were cell killing, geneconversion and reverse mutation. Contrary to expectation, nogrowth occured in the cultures even after 48 hrs. of incubation.The cell retained viability but were only arrested in growth.When subcultured in the presence of sub-optimum levels of bothadenine and Ni methyladenine complete growth occured. However,no enhancement in the induction of gene conversion or backmutation was observed in these cultures.

Experiments with tritium labelled Ni methyladenine showedthat it is taken up by the cells. Hence it is speculated thatthe ineffectiveness of methyladenine is due to their not beingutilised as substrates in the synthesis of DNA by the salvagepathway. This is important for the assessment of the biologicaleffects of DNA precursor pool alkylation.

2 • 10 Metabolic fate of Nt ine thyladjenine _i_n_. yeastauxotrophic _ t_o_a den in e

M.S.S. Murthy and V.V. Deorukhakar

Metabolic fate of Ni-methyladenine in yeast with respectto its incorporation into RNA has been studied. Chromotographicanalysis of the PCA soluble and insoluble fractions of cellsgrown in the combined presence of adenine and H3 labelled Ni-methyladenine show that (a) Ni • nn-thyladeninecan enter the cells,(b) however it is very poorly utilized by the salvage pathway fornucleic acid synthesis and (c) the inhibition occurs probably atthe first stage of conversion of the methylated base to thecorresponding nucleotide. These studies explain the previously

: 13 i

reported ineffectiveness of methylated adenines to support growthof yeast cells auxotrophic to adenine.

PUBLICATIONS

1. Occupational exposure to chemical carcinogens: A need forregulation, M.S.S. Murthy, N. Sankaranarayanan, SeventhAnnual Conference of EMSI Madras (1982) 25.

2. Induction of gene conversion in yeast by mutagens andcarcinogens, M.S.S. Murthy, Workshop in the Evaluation ofMutagenic and Carcinogenic Potential of Environmental Agents,Bombay (1982) 4.

3. Evaluation of genetic risks from alkylating agents on thebasis of haemoglobin alkylation, M.S.S. Murthy, Ibid, 105.

4. Co-ordinated research program on the comparative biologicalhazards from low level radiations and major chemicalpollutants, Final Report to IAEA Contract No. 1961/R5/RB,M.S.S. Murthy, U. Madhvanath, A.M. Mohan Rao, N. SankaraNarayan, K.B. Anjaria (1982).

5. Hyperthermia-mechanisms and use in radiotherapy (invitedpaper),B.S. Rao, DAE Symposium on Modifiers ofRadiosensitivity in Radiotherapy, Madras (1982) 43.

6. Modification of mutation induction in Chinese hamster ovc rycells exposed to gamma radiation, B.S. Rao and L.E. Hopwood,Radiat. Res. 91 (1982) 369.

7. Genetic control of budding cell resistance in diploid yeastsaccharomyces cerevisiae exposed to gamma radiation, B.S. Raoand N.M.S. Reddy, Mutation Res. 95 (1982) 213.

8. Modification of mutation frequency in plateau phase CHO cellsexposed to gamma radiation during recovery from potentiallylethal damage, B.S. Rao and L.E. Hopewood, Int. J. Radiat.Biol. 42 (1982) 501.

9. Absence of dose-rate effect and recovery from sub-lethaldamage in rad 52 strain of diploid yeast Saccharomycescerevisiae exposed to r-rays, N.M.S. Reddy, K.B. Anjariaand P. Subramanyatn;Mutation Res. 105 (1982), 145.

10. Mode of inactivation of cells by heat: A new concept^N.M.S.Reddy, K.B. Anjaria and V.V. Deorukhakar, AMPI Bulletin, 7(1982) 227.

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11. A factor which can lead to false positives in Ames test,{Abstract) K.B. Anjaria and M.S.S. Murthy, Annual Conferenceof Environmental Mutagen Society of India, Madras (1982) 18.

12. DNA alkylation-site specificity for mutagenesis in mammaliancells (Abstract) M.S.S. Murthy, 15th International Congressof Genetics, New Delhi (1983) 299(A).

13. Radiation equivalence of genotoxic chemicals : Validation inmammalian cell lines, M. S-S.Murthy, Mutation Res. 94 (1983)189.

14. Radiation equivalence as a basis for estimation for risk fromgenotoxic chemicals (Abstract) M.S.S. Murthy, Indo-FRGSeminar on Methodological Application of Radiation andchemicals in the Environment, BARC, Bombay (1983).

15. Inhibition of repair of premutational lesions in plateauphase Chinese hamster cells exposed to gamma radiation, B.S.Rao and L.E. Hopwood, Radiat. Environ. Biophysics 22 (1983)21.

16. Effect of hypoxia on the recovery from the damage induced byheat and radiation in CHO cells, B.S. Rao and L.E. Hopwood,Sixth Conference of Medical Physics, Srinagar (1983) 14.

17. Recovery from mutational lesions in CHO cells, B.S. Rao andL.E. Hopwood XV International Congress of Genetics, NewDelhi (1983) 319.

18. Identification of genetic loci associated with recovery fromradiation damage in diploid yeast, B.S. Rao and N.M.S. Reddy,Ibid (1983) 747.

19. Effect of hyperthermia on the induction of gene conversion inyeast cells exposed to gamma radiation (Abstract), B.S. Rao,K.B.Anjaria and V.V. Deorukhakar, XI Conference IndianBiophysics Society, Hyderabad (1983) 3.

20. Interaction between hyperthermia and gamma radiation ina radiosensitive mutant strains of diploid yeast, V.V.Deorukhakar and B.S. Rao, AMPI Bull. 8 (1983) 21.

21. Radiation equivalence of chemicals, M.S.S. Murthy,Encyclopaedia of Occupational Health and Safety, 2,International Labour Organisation, (1983) 1850.

j 15

22. Combined mutagenic action of chemicals and radiation indiploid yeast, K.B. Anjaria and U. Kidhvanath, Mutation Res,120 (1983) 111.

23. Effect of soium bisulfite on the repair of gamma ray inducedpotentially lethal damage in yeast, (Abstract), K.B. Anjariaand M.S.S. Murthy, VIII Annual Conference of EnvironmentalMutagen Society of India, Hyderabad (1983) 1.

24. Recovery from heat damage in stationary and log phase diploidyeast cells under growth and non-growth conditions, N.M.S.Reddy, K.B. Anjaria, V.V. Deorukhakar and B.S. Rao, Int. J.Radiat. Biol. 43 (1983) 465.

25. On the induction of gene conversion in yeast by sodiumbisulfite under radical reaction conditions, M.S.S. Murthy,V.V. Deorukhakar and K.B. Anjaria, Fd. Chem. Toxic, 21(1983) 499.

26. Mutagenicity studies of nitrazepam and its metabolite inSalmonella microsome test, R.L. Gupta, G. Lai, T.R. Juneja,M.S.S. Murthy, K.B. Anjaria and N. Sankara Narayanan. CurrentScience, 52 (1983) 424.

27. Role of extracellular pH on the modificatioin of OERassociated with gamma radiation, V.V. Deorukhakar, K.3.Anjaria and B.S. Rao, AMPI Bull. 9 (1984) 12.

28. Effect of hypoxia on the lethality of mammalian cells uponcombined gamma irradiation and hyperthermia. B.S. Rao andL.E. Hopwood, VII Medical Physics Conference, Calcutta(1984) 18.

29. Relationships between ethylation of haemoglobin, ethylationof DNA and administered amount of ethylmethane sulphonate inmouse, M.S.S. Murthy, C.J. Calleman; S. Osterman - Golkar, D.Sagerback and K. Svensson; Mutation Res. 127 (1984) 1.

30. Case study of a radiation incident involving a Co-60radiographic camera, P.K. Marathe, N. Sankara Narayanan andV.G.R. Subramanian, Bull, of radiat. Prot. 7 (1984) 69.

31. Effect of hypoxia on the recovery from damage induced by heatand radiation in plateau phase CHO cells, B.S. Rao and L.E,Hopwood, Radiat. Res. 101 (1985) 312.

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32. Effect of hypoxia on the repair of damage induced by heat andradiation in cultured mammalian cells and its possibleimplications in radiotherapy. B.S. Rao, VII Congress ofAROI, Bangalore (1985) 18.

33. Yeast in radiation biology, B.S. Rao, Yeast Biotechnology,Eds. R.K. Vashishat 6 P. Tauro (1986) 66.

34. Genotoxicity of selenite in diploid yeast (Abstract) K.B.Anjaria and U. Madhvanath, X Annual Conference ofEnvironmental Mutagen Society of India, BARC, Bombay (1985)181.

35. Mutagenic interaction between ionising radiation andchemicals in diploid yeast, K.B. Anjaria, M.Sc. Ther".,Bombay University (1985).

36. Failure of exogenous methylated adenine to induce cytotoxicand genotoxic effects in yeaat auxotrophic to adenine, M.S.S.Murthy and V.V. Deorukhakar, J. Biosci. 9 (1985) 223.

37. Pate of exogenously supplied 1 methyladenine in yeastauxotrophic to adenine, M.S.S. Murthy and V.V. Deorukhakar,XI Conference of EMSI, Madras (1986) S-7.

38. Effect of anoxia on cellular uptake of drugs, V.V.Deorukhakar and M.S.S. Murthy, Conference proceedings, AMPIBull. (1986) 365.

39. Induction of mitotic gene conversion in saccharomycescerevisiae by cigarette smoke condensate (CSC) N. SankaraNarayanan and B. S. Rao, Ibid (1986) 53.

40. Radiation Carcinogenesis, B.S. rao Proceedings of theworkshop on ICRP and Related Publications, Bombay (1986) 60.

41. Nonstochastic effects of radiation, B.S. Rao, Proceed:' js ofthe workshop on ICRP and Related Publications, Bombay (1986)80.

42. Hyperthermic inhibition of recovery from radiation damage indiploid yeast (Abstract), V.V. Deorukhakar, B.S. Rao and K.B.Anjaria, Symposium on Biophysical Aspects of Cell Structureand Function, Lucknow (1986) 65.

j 17 :

43. Genotoxicity of hypoxic cell sensitizers; An enquiry(Abstract) M.S.S. Murthy and K.B. Anjaria, Asian RegionalConference on Medical Physics, Bombay (1986) 381.

44. Absence of synergistic interaction between cigarette smokecondensate and radiation for the induction of genotoxiceffect in yeast, B.S. Rao and N. Sankara Narayanan, XIAnnual Conference of EMSI, Madras (1986) 55.

45. Effect of sodium selenite on methyl methane sulphonateinduced gene conversion in yeast (Abstract), K.B, Anjariaand U. Madhvanath, XI Annual Conference of EnvironmentalMutagen Society, Madras (1986) 56.

46. Yeast as a tool in screening environmental chemicals fortheir geno-toxic potential to man, M.S.S. Murthy, YeastBiotechnology, Eds.R.K. Vashishat and P. tauro (1986)58.

47. Effect of cycloheximide on the expression of gene conversionand cell killing induced by N-methyl-N'nitroso-N-nitrosoguanidine and gamma radiation in yeast, K.B. Anjariaand M.S.S. Murthy, XII Annual Conference of EnvironmentalMutagen Societyd of India, Hisar, (1987) 53.

48. Search for an inducible component in the recombination repairin yeast exposed to gamma radiation and two mutagenicchemicals, M.S.S. Murthy, K.B. Anjaria and V.V. Deorukhakar,ibid, (1987) 54.

49. Influence of anoxia on the lethal and recombinogenic effectsof mutagenic chemicals in yeast, V.V. Deorukhakar and M.S.S.Murthy, ibid, (1987) 60.

50. Effect of caffeine on the gamma radiation induced geneconversion and back mutation in yeast, B.S. Rao, N.Sankaranarayanan and K.B. Anjaria, ibid, (1987) 45.

51. Interaction between 3H beta and *°Co gamma rays in theinduction of genetic damage in yeast cells, NationalSymposium on Radiation Biology, Manipal, B.S. Rao, K.B.Anjaria, N. Sankaranarayanan and U. Madhvanath, (1987) 65.

52. Modification of radiation induced gene conversion in yeast byhyperthermia, K.B. Anjaria and B.S. Rao, ibid, (1987) 57.

: 18 :

53. Oxygen enhancement ratio (OER) for the induction of forwardmutation in Chinese hamster ovary cells, B.S. Rao and L.E.Hopwood, ibid, (1987) 67.

54. Late effects of low level radiation exposure in mammals,B.S.Rao, ibid, (1987) 71.

55. Risk evaluation for female radiation workers of medicalinstitutions in India, K.S. Shenoy and B.S.Rao, ibid,(1987) 93.

3. Dose modifier studies

D. Krishnan, Kamala Gopakumar & Gouri Unnikrishnan

3.1 Studies on radiolvsis of aqueous DNA

Kamala Gopakumar, Gouri Unnikrishnan & D. Krishnan

Simultaneous estimation of base damage and phosphaterelease from DNA & TMP on gamma irradiation showed that there isan inverse correlation with respect to these two end points asdose icreases. During this period this effect was further testedby comparing the results of TMP with the results of irradiating amixture of thymine (T) and ribose phosphate (RP) . Theoreticalprediction of the results based on rate constants of thecomponents in general agreed with the experimental results.

With a view to increase the sensitivity of estimation ofinorganic phosphate (Pi) in DNA irradiation experiments, thetraditional Berenblum and Chain method was improved upon. Thismethod can measure as low as 10*7 M of phosphate. Use of thismethod enable to have more confidence in the dose versus Pirelease in DNA irradiation to a dose of as low as 5 kilorads.

The effect of added chemical modifiers (viz cysteine,glutathione, NEM and flagyl) on Pi release from aqueous DNA in O2and N« was studied. Enhanced protection by SH compounds in N2was observed. This is due to H donation from SH compoundeffective only in N2. This property is responsible for theobserved fact that flagyl sensitizes Pi release only in N2 andthat too only in combination with SH compounds.

: 19

The non-linear dose response graph for Pi release fron; DNAbecame linear when the irradiated DNA solution was treated in0.1N NaOH before Pi i estimation. The increase in Pi was muchhigher (about 3 times) for an O2 saturated solution than for N2saturation. This resulted in an OER of approximately 3 (from anOER of less than 1) This was similar to OER for strand breaks inDNA (which is usually in alkali).

3 . 2 Ozone and radiation possibly..appl.icat ion in_.J!!LajLte.. watertreatment

Gouri Unnikrishnan, Kamala Gopakumar and D. Krishnan

Ozone from an electrical spark type apparatus was passuothrough DNA solution either before or during gamma irradiation.The Pi release showed a sensitization factor of about 1.5 to 4depending on ozone concentrations (1.5 x 10-fcM to 6 x 10-*M). Thesynergistic effect of ozone on Pi release (indicative of t:h*degradation of the niacromolecule) suggests that this could beuseful in sewage treatment.

3 . 3 Rad.iat_ij5.n xis.i<_^e7tim.ate.s for Jkeukaemia.t. .Atom-bomb

D. Krishnan, Gouri Unnikrishnan and P.K. Marathe

Published results of leukaemia fatalities were compiled.The old and the revised atom-bomb dosimetry data were alsoincluded. A graph of leukaemia versus bone marrow dose wasconstructed based on all these data. Assuming a linear non-threshold nature of graph, an upper & lower estimate forleukaemia risk were determined. The lower limit wasapproximately equal to the risk coefficient recommended by ICRPpublication 26. The mean was about 3 times higher than this.This suggests that ICRP values appropriate to a model of low LETcarcinogenesis based on linear-quadratic relation.

3 • 4 Internal dosimetry._caJLcu.lat.:Lon.s

Gouri Unnikrishnan and D. Krishnan

An attempt was made to arrive at an apparent half life(Tapp) extracted from the complicated eliminatioin equation (orretention function). This is calculated on the basis of asimplified hypothetical exponential elimination model for someselected radionuclides. The effective mean life calculated inthis manner can form a link between the old MPBB and the new ALIvalues. It is suggested that a quantity'annual limit of uptake'(ALU) incorporating fi or f» values) is more appropriate than ALIfor all body burden measurements qao values equivalent to MPBB(but based on ICRP Publication-30) making use of ALU and Tappvalues were calculated. q:i 0 is that activity of a radionuclide

: 20 t

which, if present constantly for one year, will give rise to aweighted committed dose equivalent of 5 rent in a year. A bodyburden measurement at any time can be compared with qao to decidethe seriousness or otherwise of an intake, qso was calculated for15 radionuclides.

PUBLICATIONS

1. Some suggestions for radiolysis of cysteine by absorptionspectrophotometry (Abstract), Kamala Gopakumar, GouriUnnikrishnan and D. Krishnan, Radiochemistry and RadiationChemistry Symposium, Pune (1982).

2. A comparison of radiation effects in aqueous solutions of DNAand its constituents (Abstract), D. Krishnan, KamalaGopakumar and Gouri Unnikrishnan, Radiochemistry andRadiation Chemistry Symposium, Pune (1982).

3. Radiotherapeutic trials with hypoxic sensitizers (Abstract),D.R. Singh, D. Krishnan and U. Madhvanath, IVth Congress ofAssociation of Radiation oncologists of India, Madras, Dec.(1982)

4. Alkali labile phosphate release from irradiated DNA-effect ofGlutions (Abstract), Kamala Gopakumar, Gouri Unnikrishnan andD. Krishnan, Radiochemistry and Radiation ChemistrySymposium, Bombay, Dec. (1985).

5. Radiation sensitization of phosphate release in DNA by flagyland NEM : significance of SH groups (Abstract), GouriUnnikrishnan, Kamala Gopakumar and D.Krishnan, Radiochemistryand Radiation Chemistry Symposium, Bombay Dec. (1985).

6. Correlation between the radiolysis of TMP and mixture ofthymine and ribose phosphate (Abstract), K. Gopakumar, G.Unnikrishnan and D. Krishnan, Radiochemistry and RadiationChemistry Symposium, IIT, Kanpur (1985) 286.

7. Effect of scavengers on gamma radiolysis of thymine in O2(Abstract), K. Gopakumar, G. Unnikrishnan and D. Krishnan,Radiochemistry and Radiation Chemsitry Symposium, IIT, Kanpur(1985) 290.

: 21 t

Leukaemia from radiation : Comparison of ICRP andrevised A-Bomb and other data (extended synopsis), GouriUnnikrishnan and D. Krishnan, 12th Annual meeting of IndianAssociation for Radiation Protection, Bombay, March (1985)

9. Estimation of some corrections in ALI and DAC for Indianconditions for unsealed radionuclides, G.N. Shaikh, U.C.Mishra and D. Krishnan, Phys. Bull. 11 (3-4) (1986) 540.

10. Patient dose in diagnostic medicine : How to quantitato,(Abstract), D. Krishnan, Med. Phys. Bull. 11 (1986) 456.

11. A theoretical approach to the effect of dose modifiers onfractionation in radiotherapy (Abstract), D. Krishnan, D.R.Singh, Med. Phys. Bull. 1 (1986) 339.

12. Routine internal monitoring and ALI, D. Krishnan and GouriUnnikrishnan, letter to the Editor, Radiation ProtectionDosimetry, 12 (1986) 277.

13. Estimation of inorganic phosphate in aqueous solutions ofDNA: a modification of the Berenblum-Chain method,M.H.Doshi, G. Unnikrishnan, N.S. Bhandari and D. Krishnan, J.Raciianol, Nucl. Chem. Letters 103 (1986) 291.

14. Ozone plus Radiation on aqueous solution of DNA - Asuggestion for treatment of water, Gouri Unnikrishnan, KamalaGopikumar and D. Krishnan, Radiat. Phys. Chem. 28 (1986) 281.

4. Tneoretical studies

4.1 1r°JP:P..utttli_satipn of advisory .servicesi data

c.P. Raghavendran , D.P. Bhatia and P.S. Bagarajan.

Work on computerising the data of a part of advisory

: 22 :

service work load was done. For this purpose two Fortranprograms, one each for medical teletherapy and industrialadvisory institutions were developed. These are in dialoguemode. The programs read the data from medical and industrialinstitution files and presents whatever is asked Cor jn thescreen and provide print output.

4.2 Neutron spectrum calculations in Dhruva reactor

P.S. Nagarajan and V.K. Sundaram

Using MORSE-CG and ANISN codes the neutron spectraldistributions in the ion chamber basket of DHRUVA reactor werecomputed. This is a very deep penetration problem and a hybridmethod was developed for the same.

4.3 Electron transport computations

M.A. Prasad

A new Monte Carlo method for electron transport wasdeveloped. This method has certain advantages over earliermethods in that it requires lesser data storage and also islikely to be more accurate at interfaces. Analytical expressionswere obtained for the variance associated with a contributionMonte Carlo game and it was shown that simple geometricalsplitting is more efficient than contribution Monte Carlo.

Investigations were carried out in the Glauberapproximation, Second Born approximation etc. For example, itwas shown that the complete first order Wallace correction to theGlauber approximation diverges in some cases. Walds Lemma wasgeneralised to include correlated random walks and partialabsorbing boundaries. Asymptotic expressions were obtained forcorrelated random walks on a one dimensional lattice with trapsand for restricted random walks on one dimensional random chains.

4.4 Computations of electron energy degradation in Kr.Xe andwater vapour

Dayashankar

A theoretical study of the problem of electron energydegradation in krypton and xenon was carried out using MonteCarlo method from the point of view of understanding thestochastic nature of the degradiation process. Quantities of

i 23 :

microdosimetric interest such as the Fano factor, a parametercommonly used for characterizing the ionization yieldfluctuations, and the probability distributions of the number ofionization events were obtained for a number of source energies.Electron degradation spectra for various source energies werealso calculated. The degradation spectrum plays a basic role inenergy degradation problems because it serves as an adjointfunction determining the mean yield as well as the informationabout the yield fluctuations.

A theoretical study of the spatial aspects of electronenergy degradation in water Vapor was carried out in the energyrange from 30 eV to 1 MeV. The simulation of electron transportwas carried out by Monte Carlo method considering variousprocesses of energy loss at molecular level in a detailed manner.The complex four dimensional spatial yield spctral distributionobtained from the computations was represented by a number ofsimple analytic forms which display the progession of shapes withincreasing incident energy. These forms were used to calculatethe spatial distributions of the initial species created byelectron energy deposition in water. The influence of diffusionin the steady state is calculated with the help of a Legendrepolynomial expansion of the source function. These analyticsource and concentration distributions can serve as conventionalinputs for studies of the chemical and biological stages ofradiation action.

PUBLICATIONS

1. Shielding calculations below 100 KV, C.P. Raghavendran, P.S.Nagarajan and G. Venkataraman, Health Physics 42 (5) (1982)717.

2. Applications of Monte Carlo methods in neutron dosimetry,P.S.Nagarajan, Workshop on Monte Carlo methods, BARC, BombayJanuary (1982).

3. Second order eikonal cross sections for the excitation ofatomic hydrogen, K. Unnikrishnan and M.A. Prasad, J. Phys. B15 (1982) 1549.

4. Ionization yield in xenon due to electron impact,Dayashankar, Physica 1134 C (1982) 1237.

5. Energy degradation of electrons in krypton, Dayashankar, M.A.Prasad and K. Unnikrishnan,Phys. Letters 90A (1982) 402.

6. On the second Born forward scattering amplimede for elasticelectron hydrogen collosions, K. Unnikrishnan and M.A.Prasad, Ind. J. Phys. 57 B (1983) 276.

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7. Path-length dependent flux from random with theory, K.Unnikrishnan and M.A. Prasad, Phys. Let. A. 97 (1983) 131.

8. Fluctuations in the ionisation yield in finite regions ofmatter due to electron degradation, M.A. Prasad and K.Unnikrishnan, Phys. Rev. A. 27 (1983) 536.

9. Eikonal expansion for inelastic scattering, K. Unnikrishnanand M.A. Prasad, J. Phys. B. 16 (1983) L. 781.

10. A different approach for the application of Monte Carlomethods to electron transport, S.K. Gupta and M.A. Prasad,Nucl. Sci. Eng. 90 (1983) 256.

11. Neutron depth dose calculations for treatment planning infast neutron radiotherapy, G. Burger, A. Morhart and P. S.Nagarajan, Report of the advisory Group Meeting on Advancesin Dosimetry of Fast Neutrons and Heavy Charged Particlesfor Therapy Applications, IAEA, Vienna (1984) 53.

12. Quantities relevant for external neutron irradiation inradiation protection, G. Burger, A. Morhart, P.S. Nagarajanand A. Wittmann, CENDOS 84-1, Euratom, Commission of theEuropean Communities, Luxembourg (1984).

13. Biareel random walls on a multidimensional lattice withabsorbing boundaries, M.A. Prasad and K. Unnikrishnan,Physica A. 127 (1984) 659.

14. Random walk on a one dimensional lattice with a randomdistribution of traps, M.A. Prasad and K. Unnikrishnan,Phys.Lett. A. 100 (1984) 19.

15. Electron-hydrogen scattering in an intense laser field, K.Unnikrishnan and M.A. Prasad, Phys. Rev. A 29 (1984) 3423.

16. Estimation of population variance in contribution MonteCarlo, P.K.Sarkar and M.A. Prasad, Nuc. Sci. Eng. (1984) 136.

17. Occupancy time for correlated random walks with partiallyabsorbing boundaries, K. Unnikrishnan and M.A. Prasad^ActaPhysica Austriaca 56 (1985) 253.

18. Eikonal expansion for inelastic scattering, K. Unnikrishnanand M.A. Prasad, J. Phys. B. 18 (1985) L. 699.

19. Asymptotically exact solution <&f the one-dimensional trappingproblems with correlation, M.A. Prasad and K. Unnikrishnan,Phys. Rev. A 31 (1985) 523.

20. Yield and concentration microplumes for electron impact onwater, A.E.S. Green, Dayashankar, P.F. Schippnick, D.E. Rioand J.M. Schwartz, Rad. Res. 104 (1985) 1.

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21. Spatial aspects of electron energy deposition in water vapor(Abstract) A.E.S. Green, Dayashankar, P.F. Schippnick andD.E.Rio, Radiation Research Society Annual Meeting, LosAngeles (1985).

22. A restricted random walk on a one-dimensional random chain,M.A. Prasad,Phys. Lett. A 117 (1986) 217.

23. Electron impact cross sections and spatial aspects ofelectron energy degradation in water vapor, Dayashankar,S.T. Suh and A.E.S. Green, Int. J. Quantum Chem. Symp. 20(1986) 547.

24. Analytic electron impact cross section^for water vapor(Abstract). A.E.S. Green and Dayashankar, 50th Annual Meetingand Golden Anniversary of the Florida Academy of Sciences,Gainesville, Florida (1986).

25. Yield spectra in water vapor for electron impact (Abstract)Dayashankar, S.T. Suh and A.E.S. Green, Sixth NationalWorkshop on Atomic and Molecular Physics, Varanasi (1986) 75.

26. Stopping cross sections of Krypton and Xenon for low energyelectrons, Dayashankar, Ind. J. Pure & Applied Phys. 25(1987) 363.

27. A Hybrid approach to very deep penetration problems inshielding and dosimetry, P.S. Nagarajan and V.K. Sundaram,Sixth Symposium on Neutron Dosimetry, Neuherberg, October(1987).

28. Suggested refinements to the ICRU quantities. The energyimparted and the energy deposit in the context of low energyneutron radiation. P.S. Nagarajan, Sixth Symposium on NeutronDosimetry, Neuherberg, October (1987).

29. A comparative study of pseudo and quasi random sequence forthe Solution of integral equations, P.K. Sarkar and M.A.Prasad, J. Comput. Phys. 68, (1987) 66.

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B. RADIATION METROLOGY SECTION

P. Gangadharan

The objective of the section is to maintain and developNational Standards for radiation measurements, whose accuraciesare traceable to and comparable with international standards.This activity is a statutory obligation and demands continuousand intensive research. One reason for the active engagementof the section in rdiation measurements and dosimetry was therecognition that high standards in these would be required toachieve traceability to international standards and acceptablecure results in radiation therapy. Another reason was theincreasing interests of Indian public in the problem of radiationprotection. Moreover the activity of the section has to bemaintained to effect the change from the old radiation units suchas Roentgen, Rad, Rem and Curie to the new SI units such asCoulomb/Kg, Gray, Sievert and Becquerel. To realise thisobjective additional standards have to be developed. The schemeof calibration heirarchy and the pivotal role of the section aredepicted in Fig.l.

Various standards developed and maintained at the RadiationMetrology Section (RMS) are listed in Table 1. These standardswhich are used for calibration are periodically intercomparedwith international standards to ensure accuracy and traceability.

Table 1: Primary standards maintained at R.M.S.

Free air chamber : Exposure ± 1%(for X-rays)

Cylindrical Graphite : Exposure (± 1%)Chamber (for Co60 rays)

Graphite Calorimeter : Dose ( ± 1%)

4n3 gamma coincidence : Activity { ± 0.2%)Counter

Manganese bath : neutron yield ( ± 1%)

Neutron telescope : Fast neutron flux ( ± 3%)

Graphite Assembly : Thermal neutron flux i 2%

This report, which is divided into five parts, describes inbrief the technical activities of the section.

1. Radionuclide sjka.ndards.

P.K. Srivastava, H.K. Sahoo, R. Nathuram and G.D. Khera

The R.M. Section has established primary standards of acomprehensive range of radionuclides decaying by a,($-, &• , andgamma emission as well as by electron-capture. Considerableamount of R&D has been done for the development of special

27 :

1

2 A a z

n s -

HOSPITALS

A N D

PRIMARY

St AHDHDS

* T

Pig. 1 . Calibration scheme

: 28 s

techniques and instruments required for the standardization ofradionuclides to the highest accuracy achievable with the presentstate of art. These have been rigorously tested for theiraccuracy, precision and reliability over the years. The nationalstandards have been compared with those of other standardslaboratories of the world under a program of internationalintercomparison.

Standards of radionuclides have been supplied to users ofradioisotopes in various Divisions of BARC as well as constituentunits of the DAE family, so that, almost all measurements onradioisotopes and interpretation of results in these laboratoriesare related directly or indirectly to the standards supplied bythis Section.

1.1 Dilution and qource-preparation

The most satisfactory physical form of a standard ofactivity is a stable solution in a flame sealed glass ampoule.For the standardization of such a solution, dilution and sourcepreparation are carried out for preparing samples suitable forcounting in nuclear counting systems.

Dilution and source preparation are carried out on constantsensitivity balances installed on vibration-free platforms in anactive laboratory. In general, four dilutions are made from theoriginal solution using specially prepared diluent so that thechemical composition is not altered. About 10 sources arepreparedby the Pycnometer method on a microbalance. The accuracyof dilution and source-preparation is about 0.1%.

1. 2 Counting techniques

Almost every radionuclide needs a special technique ofstandardization because of differences in decay-schemes and inchemical behaviour. Therefore, special methods have beendeveloped for the standardization of specific radioisotopes.However, to cover the most radionuclides of interest, thefollowing counting techniques have been set up.

1.2.1 Efficiency-tracer technique

The efficiency-tracer technique was developed for theprimary standardization of pure beta emitters, like Phosphorus-32, and beta emitters followed by, delayed gamma rays, likeCaesium-137. In this technique, a suitable beta-gamma emitter isadded to the source of pure beta emitter and is used for tracingthe beta efficiency of the sample. A number of samples withdifferent beta-efficiency are prepared and counted inconventional 4 n,p,gamma coincidence system. The observedactivity of the pure beta source is plotted against the beta-efficiency of the tracer. A linear Least Squares fit is used toextrapolate it to 100% beta efficiency to get the disintegration-rate of the sample. The counting system accepts sources havingan activity in the range from 1 to 30 kBq. The overall accuracyof standardization is of the order of 0.1 percent.

: 29 t

A dedicated microcomputer has been added for dataacquisition, statistical analysis and calculation of the activityof the sample by Bryants method. It prints the raw data as wellas calculates results from the source and the background. Thecriteria of rejection of a reading is also included in thesoftware.

1.2.2. Large diameter 4 n proportional counter

A 30 cm diameter cylindrical 4 n gas flow counter has beenconstructed for the standardization of Cadmium-109 sources bymeasuring the number of conversion electrons in the presence ofX-rays and Auger electrons. Cadmium-109 (half-life 464 ± 1 days)decays to Silver-109m by electroncapture, which de-exites byemission of highly converted (96%) gamma rays of 88 keV. Thepath length in this counter is such that upto about 90 keVelectrons can spend their full energy in the sensitive volume.The lower energy X-rays and Auger electrons from electron captureevents are not in coincidence with conversion electrons and henceare discriminated from them. The self absorption is negligiblebecause the conversion electrons are of relatively high energy.The 4 n counter has been designed and constructed.

1.2.3. Re-entrant type gamma ionization chamber

A re-entrant type high pressure gamma ionizction chamber hasbeen set up as a secondary standard instrument. It cosists of acylindrical ion-chamber having volume of about 10 litres with are-entrant cavity of 5 cm diameter resulting in almost 4 ngeometry. The sensitive volume is filled with Argon to apressure of about 20 atmospheres. The current from the ion-chamber is measured with a Varacter bridge type Electrometer.The chamber is shielded with 5 cm thick lead enclosure to makethe detection efficiency independent of various in surroundingsand to ensure radiation safety.

The 4 n geometry has resulted in high detection efficiencyand low sensitivity to changes in source-position or source-size.Also, it has a high inherent precision and large dynamic rangefrom 10 kBq to 500 MBq.

The ionization chamber has been calibrated with more than 20radionuclides decaying by gamma emission to an accuracy of 1 to3%. A plot of calibration factor versus gamma energy is used forcalculating the calibration factor for radionuclides for whichthe direct measurement is not available. The ion chamber has beencompared with international standards for several radionuclides.The reproducibility of the system as measured with a speciallyprepared old Radiun-226 source, in which daughter products havereached an equilibrium with parent and half-life remains 1600years, has been found to be better than 0.03% per year. Thesystem has been used for calibrating a large number of samples ofradioisotopes.

: 30 :

1.2.4. Well scintillation spectrometer

For the standardization of sources having an activity ofless than 10 kBq, a 76 mm x 76 mm Nal (Tl) crystal having a wellof 25 mm x 50 mm has been setup. The variation of the detectorefficiency as a function of source position and source volume hasbeen studied. The system has been calibrated with a number ofradionuclides to an accuracy of 2 to 5%. The reproducibility ofthe system, as measured with a reference source of Caesium-137,has been found to be better than 1%.

1 * 3 International intercomparison

1.3.1 Caesium-134

International intercomparison of the activity measurementsof Caesium-134 was organised by the Bureau International desPoids et Measures (BIPM), France. Twenty four national andinternational laboratories of the world, including BARC, tookpart in this intercomparison.

The solution of Caesium-134 was standardized by the 4n,p,gamma coincidence system using an "efficiency extrapolationtechnique" which was developed for this radionuclide. Apolynomial Least-Squares fit was used for this purpose. Ourresult

A = (832.1 ± 2.5) Bq.mg-»was sent to the BIPM.

The results received from all standards laboratories wereanalysed by the BIPM and a report psublished by them has proposeda world mean of

A = (830.0 ±1.4) Bq.mg.-1

on 1980 -10-15, ooh UT. The results are shown in Fig. 2. It isseen that BARC standard of Caesium-134 is in agreement with theinternational value within 0.25%.

1.3.2. Caesium-137

Primary standards of Caesium-137 are of great importance forprecise radiation measurements because, due to its long half-life(30.39 ± 0.27 years) and single gamma ray (661.6 KeV), thisradionuclide is widely used for the calibration of gamma rayspectrometers and other nuclear radiation detectors. In view ofthese, an international intercomparison of activity measurementof a solution of Caesium-137 was organized by the BureauInternational des Poids et measures (BIPM), France in which 19national and international laboratories, including BARC, haveparticipated.

Standardization of this radionuclide is complicated due tothe fact that the 661.6 KeV level in the decay of Caesium-137 ica meta-stable state (2.55 min) and hence coincidence countingcannot be directly applied. To overcome this difficulty, anefficiency-tracing technique (using Caesium-134 as a tracer) wasused.

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Each participant received from PTB, West Germany, oneampoule of Caesium-137 solution for standardization and oneampoule of Caesium-134 to be used as an efficiency tracer. Bothsolutions had similar chemical composition and activityconcentration.

For the absoluteprepared for counting.1 3 4 C s , ten contained1 3«Cs only.

activity measurement, 34 sources wereFourteen sources contained mixed 1 3 TCs +

1 3 7Cs only and remaining ten contained

These sources were counted on the 4 n, ft, gamma coincidencecounting system. The activity of Caesium-134 was calculated frompure 13 •'Cs sources. This was used to substract the activity ofCesium 1" * from the mixed sources which were counted byefficiency-tracer technique which involved extrapolation ofresidual beta counting rate from Caesium-137 to 100% betaefficiency of Cesium-134.

The activity concentration of the 1 3 7Cs solution wascalculated after correcting for the detection of internalconversion electrons and 661.6 JceV gamma rays in the 4 n, Pcounter. The final result

A « (605.4 ± 5.9) kBq.g'1

on the reference date (1982-05-01, 00 h UT) was aent to BIPM forintercoraparison. Other details were also sent. The uncertaintyin the final result was calculated according to the recentrecoaunendations of the BIPM.

The BIPM have analysed and compiled the results ofmeasurements and other details of different participatinglaboratories. A draft report circulated by the BIPM, shows thatthe unweighted mean of the result of 18 participatinglaboratories is

A = (604.1 ± 4.0) kBq.g-1

The total range of results of 19 participants is 2.4%. Out ofthese,the results of 15 participants are within 0.66%. Theagreement between the results of BARC and the internationallyaccepted value is better than 0.22%. The results of allparticipants are shown in Fig. 3.

1.4 List of standards

The following is the list of standards of radionuclidesestablished during the period under review.

t 33 :

FINAL RESULTS FOR 137Cs5

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The accuracy of standardization for a few radionuclides isgiven in Table No.2.

Table No.2: Some of the radionuclide standards established by RMS

RadionuclidePercentage uncertainty

Total systematic Random uncertainty Overaluncertainty at 99% C.L. uncertainty

Ajnaricium-241Barium-133Caesium-134Caesium-137Cobalt-57Cobalt-60Europiua-152Gold-198Iodine-131Iron-59Manganese-56Potassium-42Sodiura-22Sodium-24

0.230.450.250.690.820.240.790.280.320.630.500.550.680.46

0.140.230.140.280.250.180.310.190.250.350.320.310.280.24

0.370.780.370.971.050.421.100.470.570.980.820.860.960.70

1. 5 Services

1.5.1 Issue of standards

Standards of radionuclides are prepared for distributionamong users from time to time specially on the occasion ofinternational intercomparisons. These are supplied to thevarious Divisions depending on their requirement. In addition,calibration facilities are provided to those who submit theirsources for standardization. The present requirement of about 40calibrations per year is fully met. Some 18 Divisions/Sectionsof BARC and 6 outside institutions have been provided with

: 35 :

standards of radioisotopes.

1.5.2 National inter comparison with Iodj.ne-131

To coordinate the isotope measurements in our country and tomake these measurements traceable to the national primarystandards, three national intercomparisons of activitymeasurements with the radioisotope Iodine-131 were organized.Iodine-131 was chosen because it is extensively used in nuclearmedicine and has a convenient half-life of (8.02 ± 0.001) days.

The results of the three intercomparisons are shown in Fig.4. Analysis shows that there is an overall improvement inactivity measurements. Also, the number of participants hasincreased over the years.

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2. Neutron Standards

2.1 International intercomparison o£ Californium-252 neutronemission rate

M.G. Shahani, B.K. Kamboj, D. Sharma, U.V. Phadnis

Fourteen countries including India took part in aninternational intercomparison of Californium-252 neutron sourcestrength organised by the International Bureau of Weights andMeasures, France. Three Californium sources provided by theNational Bureau of Standards, U.S.A., National PhysicalLaboratory, U.K. and Idaho National Engineering Laboratory,U.S.A., were circulated to the participant laboratories.Participants were free to choose their method of standardizationand four different methods were used namely (1) Manganese bathtechnique, (2) Gold foil integration of neutron density in waterbath, (3) Associated alpha particle counting in T(d,n) reactionand (4) Fission counting of Californium source.

Detailed measurements were carried out at BARC on the NPL3ource using an improved manganese bath technique. In order tocheck the consistency of the coincidence measurements onManganese-56 a standard re-entrant high pressure ionizationchamber along with a reference Radium source was circulated. Theresults of the intercomparison are shown in Fig. 5. The BARCvalue agrees within 1% with the international mean when the inputvalues are normalised to a common set of standard cross-sectionand to a common basis for calculation of corrections.

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1A MeV neutron flux measurementinternational intercomparison

foils and i_t_s

O.Sharma, M.G. Shahani, U.V. Phadnis, B.K. Kamboj andS.K. Sadavarte

14 MeV fast neutron flux was produced and measuredabsolutely using the neutron telescope. The telescope measuresthe flux in terms of n-p scattering cross-section which isconsidered a standard cross-section for fast neutronmeasurements. The telescope was used to measure the Pe 56 (n,p)Mn56 reaction cross section at 14.7 MeV to develop Fe 56 assecondary fast neutron detector at BARC. This involved adetailed estimation of the corrections due to the elastic andinelastic scattering of neutrons. The value of this cross-section was found to be 104 ± 4% barns.

An international intercomparison of the flux measurementswith nine standards laboratories around the world was carried outthrough the auspices of NPL, U.K. The Fe 56 was used as detectorfor the flux measurement at BARC whereas the NPL, U.K. circulatedNiobium and Zirconium as the transfer standards for simultaneousirradiation during the flux measurements. This combination ofthe detectors not only measures the fast neutron flux but alsodetermines the average energy from the knowledge of the ratio ofniobium and zirconium induced activities. The results of thisintercomparison are shown in Fig. 6.

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2.3. Improvements in t_he thermal neutron fl_u>c density standard

U.V. Phadnis, M.G. Shahani, D. Sharma, B.K. Kamboj

Several improvements were carried out in the thermal neutronflux density standard established at BARC as a result of theexperience gained during the course uf its use for various R & Dand other applications. A precise calibration of the fluxdensity was carried out at various locations including thecentral cavity to make it more compatible for a wider range ofneutron detectors. It became necessary to reevaluate the fluxdensity at the central position as parameters like impurities inAm-241, change in the location of the standard and structuralchanges, resulting in a change in the reflected components of theneutron may have effected the flux density. The standard wasrecently enclosed in 0.5 mm thick cadmium shield to reduce thesurface dose which may also lead to a reduction in the flux inthe cavity. The new value of the thermal flux density in thecentral cavity is found to be 6454 ±1.3 % n/cm2 sec (January1987) based on Au 197 cross section. This value was alsocomputed using a Monte-Carlo Morse code and was found to be 6451± 11 % n/cm8 sec having an epithermal fraction of 0.03.

To accommodate large sire detectors two rectangularapertures (60 cm x 45 cm) on the front and side face have beenprovided. A 76 cm long channel has also been created at thecentre of the stack. Thermal flux values on these apertures andalong the entire channel have been measured using manganese andgold foils respectively and are shown in Fig. 7 and 8. The fluxvalues are found to be constant within 5% over a length of about30 cms on the front face.

2.4. Developement of. Indjyjjrn as a secondary standard for 14 MeVneutrons

B.K. Kamboj, M.G. Shahani, U.V. Phadnis, D. Sharma

In order to test the validity of Indium as an activationdetector for 14 MeV neutrons, an experiment was performed todetermine the 14 MeV flux from the (D,T) reaction using Indiumactivation simultaneously with Iron activation which isestablished as a secondary standard for 14 MeV measurements.

Measurements were made with a (D,T) neutron generator usingdeutron particle beam accelerated to 130 KeV and impinging onTitanium-Tritium target. The natural Indium foil (20 mm dia and5 mm thickness) aandwitched between two iron foils (17.5 mm diaand .076 mm thick) was put at O° to the deutron beam at adistance of 108 mm. Irradiation times varied from one hour tofour hours for several measurements. During irradiation neutronflux variation with time was monitored by a long counter and aplastic scintillator detector. An average correction of 0.5 *was obtained.

The 336 keV gamma of In (n,n') reaction was counted on a 30

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: 40 :

cc Ge (Li) detector. A computer code sampo was used to determinethe photo peak area of 336 keV gammas. The activity induced inthe sample was corrected for the effect of secondary neutron.The secondary neutron flux ard spectrum at the sample positionwas calculated from the knowledge of neutron cross sectionobtained from ENDF IV B file. A standard Eu-152 source was usedto obtain the absolute efficiency of 336 keV gamma for the Ge(Li) detector. Weighted mean efficiency of 3.97 x 10-8 ± 2* wasobtained corresponding to source detector distance of 10 cms.Finally neutron fluence rate was obtained from the knowledge ofcorrected saturation activity, efficiency, branching ratio andfoil weight etc.

For iron foils, neutron fluence rate was measured from theabsolute activity measurements using 4 n, (J, gamma coincidencesystem. For this purpose Fe-56 (n,p) Mn 56 cross-section valueof 105 mb ± 4.3 % at 14.75 MeV as measured in our laboratory withneutron telescope was used.

These measurements gave an average value of 1.14 for theratio of the fluences obtained using Indium and Iron foils. Thiscould b« due to a large correction for the secondary neutrons inthe case of Indium due to its (n,n*) cross-section profile.

2.5 Neutron detection using recoil proton registrationin CR-39.

D. Sharroa, U.V. Phadnis, M.G. Shahani

Due to its high sensitivity to protons over a wide range ofenergies from 0.2 MeV to 14 MeV CR-39 has a high potential to beused as a fast neutron detector. Various measurements have beencarried out to determine its characteristics in relation to theprimary standards at various energies.

The sensitivity of this detector covered with a 1 mm thicksheet of polyethylene serving as proton radiator, was measuredusing a number of laboratory neutron sources such as Am-Li, Am-B,Am-F, and Am-Be, covering an energy range of 0.46 to 4.5 MeV.For these studies the etching parameterc as found in thislaboratory were 6 N NaOH solution at 70°C for 16 hours durationcorresponding to an etched thickness of 21 micron. The doseresponse curve for this range of energy was found to be uniformwithin ± 25%. Work is in progress to determine the sensitivityof this detector to 14 MeV neutrons.

i 4 1 t

2.6 A microprocessor based on line dat* ILt. 1L- gamma coincidence set up.

processing system for

V.V. Shaha, V. Singh, U.V. Phadnis, M.G. Shahani

For the absolute standardization of various types ofdetector foils such as gold, manganese, cobalt etc. used for themeasurement of neutron flux and source strength, a dedicatedmicrocomputer has been developed. It performs on — linecalculations and obtains statistical parameters on the 4 n, 3,gamma coincidence set up. It acquires data on-line and afterreduction and processing, the results are printed out. Fig. 9.shows the block diagram of the system.

7S.Q £<lja/. COINCIDENCE SETUP

.«-!

2.7 Gamma to neutron ratio for Am-Be source

B.K. Kamboj, M.G. Shahani

A precise measurement of gamma to neutron ratio for Aa-Beneutron source was carried out. The total neutron output wasdetermined using an improved manganese bath technique and the4.43 MeV gamma ray associated with neutron producing reaction wasmeasured with a NaKTl). The experimental ratio so obtainedagrees well with the theoretically computed value. It isrecommended to us* the experimental value of this ratio namely0.56 t 6% as it is traceable to primary standard.

t 42 t

2.8 Response of precision long counter to intermediate energyneutrona

B.K. Kamboj, M.G. Shahani

The precision long counter established in this laboratoryhas been calibrated in the energy range 24 KeV to 4.5 MeV usingprimary radioactive neutron source standards such as Sb-Be, Aro-Be, Pu-Be and Cf-252 etc. These sources were absolutelystandardised with an overall accuracy of better than 2% using animproved Manganese bath pumping technique established in thislaboratory. This secondary standard was recently used todetermine the neutron emission rate and anisotropy factors of anintermediate energy neutron source developed in this laboratoryand having a mean energy of 0.53 KeV. This source was too bulkyand contained a large amount of boron. as this would require avery large self absorption correction, the bath technique couldnot be used. The response of the precision long counter for 0.53KeV neutrons was obtained by interpolation from the knowledge ofefficiencies obtained in this laboratory for 24 KeV and 300 KeV,as well as for thermal neutrons obtained from literature, and wasfound to be 3.44 ± 0.3 counts n-* cm*. Work is in progress todetermine experimentally the response of PLC to thermal neutrons.

3. Standards for Photon Beams

3.1 Primary standard for dose i Graphite Calorimeter

S.B. Naik, A. Kannan

A graphite calorimeter has been designed to serve as aprimary standard for absorbed close measurements of Co-60. Thecalorimeter consists of a graphite absorber (core) identical inshape and size to a thimble therapy chamber of 0.6 cc volume.This absorber is kept inside a 5 mm thick graphite jacket. Thecalorimeter is operated under semi adiabatic mode. Thetemperature of the jacket is always maintained constant. Thecalorimeter assembly is placed in a perspex tube identical inshape & size to an SSD probe and, this assembly is positioned ina water phantom maintained at a constant temperature. Fig. 10shows the arrangement of the graphite calorimeter system.

The perspex tube is evacuated to 10-« mm Hg pressure tominimise core-jacket heat transfer by air conduction andconvection. By maintaining the core-jacket temperaturedifference close to zero at all times, semi adiabatic operatingconditions are achieved. Small bead thermistors are used asheating elements and sensitive temperature sensors in the coreand jacket. This incidentally, also reduces the percentage ofimpurity present in the core. Absorbed dose to graphite isdetermined using accurate electrical calibration and from themass of the core. The overall accuracy in the absorbed doseestimation is estimated as ± 1.0% at a dose rate level of about50 mGy/s (5 rad/s).

j 43 t

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3.2 Standard for calibration of protection level dosimeters

P.N.M.R. Vijayam and A. Kannan

A standard for measurement of exposure at protectionfor photons of energies above 300 keV has been developed.

levels

This is a spherical chamber of about 62 cc volume made ofhigh purity reactor grade graphite and is used for exposure/AirKerma Measurements at protection level intensities. Fig. 11shows the cross section of the chamber. Corrections such asphoton attenuation and scatter in the wall, collection efficiencyetc. were experimentally determined. The ionisation current ismeasured using Townsend Balance system and the maximum estimateduncertainty in the realisation of Air Kerma is ± 1.5% as listedin Table 3, at a level of 88 uGy (10 mR). This standard is usedto calibrate reference standards which in turn are used tocalibrate field radiation monitors.

: 44 x

Table 3 : Uncertainties in the measurement of Air Kerma

Component

VolumeChargeTineAir densityHumidityWall attenuationCentre of electron productionCollision Mass stopping power ratioPolarity affectMass energy absorption coefficient ratioStem scatterSaturationW/e(1-g)

Overall uncertainty -

3.3 Calibration of radiation monitors in terms ofeauivalent units

% uncertainty

0.70.10.10.10.31.00.20.50.10.10.10.50.50.1

1.5%

dose

P.K.M.R. Vijayam, A. Kannan, P.S. Jadhavgaonkar

To facilitate calibration of radiation monitors in terms ofambient dose equivalent units as suggested by ICRU, a procedurehas been formulated for routine applications.

As a first step, the air kerma (K.)at a point isusing a primary standard under scatter free conditions.

measured

This is converted to the required ambient dose equivalent(H*) using appropriate conversion factors as given in Table 4applicable to the incident photon energy used. By substitutingthe radiation monitor in the same location, the instrumentcalibratioiifactor in terms of Sv/meter reading can be determined.

Table 4 : Conversion factors H* (10)/Ka for monoenergeticphotons of energy B

E(KeV) 1000 125 150 300 500 662 1250

HM1O/K. 1.65 1.56 1.49 1.31 1.23 1.20 1.16

i 45 :

3.4 Postal dose TLD intercomparison programme for high energymachines and Cs-137 units

A. Kannan, S.B. Naik, V.D. Kadim and J.B. Shigwan

SSDL has been carrying out since 1976, postal dose TLDintercomparison for CO-60 units usir>7 mailed TLD(LiP) capsules.The participants are asked to irradiate the TLD capsules to aknown dose (usually 200 cGy) in a standard Hater phantom at 5 cmdepth on a particular date and then send the capsules back to theSSDL where the dose received by these capsules is evaluated andthe results are communicated to the participants. Continuedrunning of such a programme has resulted in marked improvement indosimetry accuracy at the centres which is reflected inconsistently better results obtained in the .intercomparison.

With the introduction of medical linear accelerator inradiotherapy, the programme has been extended to these machinessine* 1983. Cs-137 units are also included since 1985, as largenuabar of them are being used for treatment purposes in ourcountry. The irradiation procedures followed in theseintercoaparisons are same as that for Co-60 units.

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: 46 t

The results of intercoroparison for high energy machines areobserved to be much better and consistent presumably due to goodmachine controls and better physics support available at theseplaces. However the results for Cs-137 units show largedeviations indicating the need for improvement in the dosimetrywith these machines. Details about the number of machinescovered and the results obtained are given in Fig. 12-14.

3.5. Patient doae monitoring

A. Kannan, S.B. Naik and V.D. Kadem

In order to estimate the accuracy of the actual dosedelivered to the patient during treatment, a programme to monitorpatient dose delivery was taken up. For this purpose, LiF in aplastic capsule was kept in a perapex container sufficientlythick to provide build-up and they were fixed by tape on theirradiated portion of the skin of the patient during treatmentfor five consecutive fractionations of the treatment. About 22patients were monitored so far. Our results indicate that for50% of the patients, the deviations were within ± 5% and for theremaining 50%, it was more than ± 5% and in some cases thedeviation exceeded ± 20%. Since the correct dose delivereddepends upon precise and careful control and adjustment of themachine parameters, proper positioning of the patient etc., suchlarge deviation indicate the extent of control exercised duringtreatment is not entirely satisfactory.

3.6 Protocol for absorbed dose calibration for clinicalradiation beams

A. Kannan, S.B. Naik, P.N.M.R. Vijayam and K.G. Rajan

Inconsistencies in the evaluation of water absorbed doseusing Co-60 exposure calibrated chambers and C^\ CE were observedby various investigators due to proximal wall effects anddisplacement corrections of individual chambers. To improve dosemeasurement accuracy, IAEA has recommended a protocol to befollowed uniformly by all radiotherapy centres. This involvedthe calibration of dosemeters in units of Air Rerma and knowledgeof wall material composition and thickness. This laboratory hasevaluated all these factors for the BARC make SSD chambers whichare in use in many centres. A calibration procedure to determinethese factors along with other factors to be uaed for doseevaluation has been formulated and measurements were made toconfirm the values. Based on these measurements a procedure fordose evaluation by the physicists is being prepared for routineapplications.

3.7. Intercomparison of! BARC standards wjLth IAEA standards

S.B. Nak, A. Kannan, P.N.M.R. Vijayam, K.N. Govinda Rajan

A) IAEA SSDL network secretariat has been organisingworkshop & seminar under their programme CARE (Coherence &

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s 48 x

Accuracy in Radiation Instrumentation) in different parts of theworld providing facility for intercomparing SSDL referencestandards against IAEA standards. Recently one such workshop &seminar was organised at SSOL, Kuala Lumpur which was attended byone of the members of RMS (SSDL, India). The following ReferenceStandards are intercompared against those of IAEA : (i) Therapylevel graphite chamber reference standard of NE - 2560 along withmeasuring assembly NB 2561 (ii) Therapy level graphite referencechambers of BARC make, and (iii) protection level 400 CCionisation reference chambers of BARC make. Intercomparisonswere carried out for Cs-137, Co-60 energy points and for severalX-ray qualities. Results of intercomparisons show good agreementof our reference standards with those of IAEA.

E) IAEA also carries out periodically intercomparison of ourdosimetry by sending TLD capsules by mail for irradiation at thislaboratory to a known dose on a specified date at »°Co energy.These capsules are irradiated in a water phantom in ourlaboratory to 2 Gy and mailed back to IAEA laboratory where thedose is evaluated. So far there has been agreement of ± 1% orbetter in our stated dose and the dose read by IAEA during allthe intercomparisons.

These periodic intercomparisons of our standards with thoseof IAEA, which show good agreement, ensure uniformity andtraceability of our standards with international standards.

4. Calibration of radiation instruments

4.1. Reference standard for protection level calibration and 60keV standard field

P.S. Rao, S.C. Misra and Vijaya Krishnan

A reference chamber has been designed for calibration ofprotection level gamma detector systems in the energy range from40 keV to 2 MeV. The chamber is made of graphite with a wallthickness of 4 nun and a volume of 100.9 cc. The response of thechamber has been computed using Burlin's general cavity theory.With this chamber radiation field intensities down to few tens ofmR/h can be standardized with an uncertainty of better than 5%.

This chamber has been used to measure the air kerma rate ofthe photon field from a 5 Ci americium source. The field (0.9mGy/h at 50 cm from the source) is used for energy responsedetermination of detector systems, as recommended by I S O .

4.2. An intermediate energy neutron source for calibration ofneutron monitors

S. Ramboj and S.C. Misra

A convenient intermediate energy source for calibration ofneutron monitors has been established using a Sb-gamma-Be neutronsource surrounded by an optimum thickness of polythene moderatorand boron carbide thermal neutron absorber. Calculations were

: 49 :

made using the MORSE code for a cylindrical Sb-gamma-Be sourceenclosed in a polythene moderator which in turn was surrounded bycylindrical boron carbide shell Pig. 15. Energies of theneutrons emitted from this source have been calculated forvarious thicknesses of polythene and boron carbide. Polythenecylinder of thickness 1.5 cm and boron carbide cylinder ofthickness 1.5 c» were optimised for a peak energy of 0.1 keV.The energy spectra of neutrons emitted in axial direction (9=0)and radial direction <e=n/» ) are given in Fig. 16. The emissionrates of the bare gamma Sb-Be and moderated source as well astheir anisotropy factors were determined using De Phanger typeprecision long counter {PLO. The experimental value of thesource strength ratio for the moderated and bare source (0.303)agreed well with the calculated value of 0.262.

I5

' 10 100 IK 10K

NEUTRON E.'J^CY ( ev)

,16 Calculated neutron apoetra

Pif.15 Neutron souroe assembly

4.3. A neutron howitzer for calibration of neutron monitors a£thermal energy

Suresh Rao, K.C. Pant and S.C. Mlsra

The neutron howitzer is a thermal neutron source withcomparitively small moderating assembly for calibration of

: 50 »

detectors in free air. It consists of a polystrene assembly ofdimensions 41 x 41 x 37 cm with a 16 x 16 x 15 cm cavity on thefront surface. A 5 Ci Am-a-Be neutron source is kept in thecavity for obtaining thermal neutron beam from the front surface.The thermal neutron flux as measured by gold foil activation at50 cm from the source was found to be 158 n.cnr's-*. Thevariation of the thermal neutron flux in vertical and horizontalaxes at various distances from the howitzer was mapped using aBF* counter and is found to remain constant to within 5% over 19and 15 cm along the horizontal and vertical axis respectively ata distance of 50 en. The system is being used as a referencestandard for calibration of neutron detectors at thermal energy.

4.4. A portable thermal neutron source for calibration ofneutron detectors and chambers

S.C. Misra, Suresh Rao, K.C. Pant and P.S. Rao

The portable thermal neutron source is a water filledperspex tank 30 x 30 x 30 cm. Two aluminium tubes attached tothe top plate project into the tank, one for positioning thesource and the other for irradiation. Calibration of neutronchambers/detectors is done by inserting them in the irradiationtube and measuring the response relative to a referencechamber/detector. With a 5 Ci Am-a-Be neutron source in thesource tube, the thermal neutron flux at the centre of theirradiatioin tube is found to be 1.22 x 10* n. cm-•sec1 asdetermined by gold foil activation. The variation in the thermalneutron flux along the central axis of the tube as determined bythe same method was found to remain constant within ± 6% over a.length of 15 cm. Using a BFs counter the average flux at theperiphery of the irradiation tube was mapped and the maximumvariation is found to be 12%. Due to its portability and simpledesign, the system is useful for calibration of neutron countersand chambers at plant sites.

: 51 :

4.5 Design and fabrication of digital pico-ammeter

A.K. Mahant, S.C. Misra and P.S. Rao

A digital picoammeter has been developed for the measurementof low level currents obtained in ionometric technique ofradiation metrology. It incorporates "rate of charge" methodwith a varactor bridge amplifier as the input device. The systemis completely automatic with print out and recycling facility.The measuring range of the instrument is from 10-13A to 10'*A.Precision obtained at current levels of few picoamperes is betterthan ± 0.1% and the estimated uncertainty in the currentmeasurement is less than ± 0.5%.

4.6 Computation of scattering correction in. calibration ofneutron monitors

S. Kamboj and S.C. Misra

The contribution of the scattered neutrons was calculatedfor a concrete flooring of thickness 20, 30, and 40 cm, fortwelve source to detector distances ranging from 10 cm to 200 cmat five different heights from the floor level (30 to 150 cm).It was calculated for detectors having flat energy respose andREM response, for seven neutron source energies from 1 keV to 14MeV and also for Am-o-Be and Sb-gamma-Be neutron sources.Calculations were done using MORSE-CG code. The variation ofscattering contribution with source to detector distance andheight from the floor level for Am-a-Be source is given in Fig.17.

iiS: lu a«

f- f

- *

;

II

II • 60 tm

II ' II! I)

112

(-in

I I •

i

u. 1IG

; iu vs S I ; A I ii£WlNC3 a

t 52 s

4.7 Studies on self-powered neutron detectors.

P.S. Rao, S.C. Hisra, Suresh Rao and A.K. Mahant

Thermal neutron sensitivity of Vanadium self powered neutrondetectors (SPND) was measured by irradiating them in APSARA. Theneutron flux at the position of irradiation (D-8) was determinedby activation of gold foils. Other parameters measured duringthe experiment included, the magnitude of prompt component in theemitter and compensating lead currents, decay constant, linearityof the emitter lead current with power and the lead resistancesduring irradiation at 400 kW power level, as shown in the Fig.18.

The thermal neutron sensitivity of the detectors has alsobeen computed, using the calculational model developed by Warren,taking into account additional factors viz.

a) neutron flux depression by the emitterb) Vs* gamma interaction with the emitter.

The Calculated and measured values ofobserved to agree within 4%.

the sensitivity are

CjfcT6CT0H REMOVED

PROMPT DECAV 3 V,

2 J '. 5

Tll.ic (WIN )

F I G . I & CECAV OF EHITTEH LEAD CURIIEMT

AFTE' l HAPIU REMOVAL OF THE

OETLXTOn FROM rtcACTOfl COHE

4.8 Scintillation spectrometer for measurement of neutronenergy

S.C. Misra, S. Kamboj, K.C. Pant and Suresh Rao

Measurement of neutron spectra is required forcharacterisation of neutron field used for calibration of neutrondose/dose rate meters. The proton recoil method with a•cintillation detector was used for measurement of fast neutronspectra. The spectra of neutron from D-D and D-T reactions war*measured with NB 102A, a plastic scintillator with no gamma

: S3 :

discrimination capability. A simple differential unfoldingmethod was used to obtain the neutron spectrum from the recoilproton distribution. Work is in progress to use NE 213, a liquidscintillator which has excellent pulse shape discriminationproperty for neutron counting in presence of gamma rays, for meas-urement of neutron energy spectra of sources having associatedgamma rays.

4 . 9 Other &tudi«.s

4.9.1 Studies or />KC SSL).

P.S 'c.-'-.o and A. Kannan

The performance evaluation of the BARC SSD has been carriedout with particular reference to its stability andreproducibility. The evaluation was baaed on the determinationof the magnitude; of limits of variation of ten influencequantities using an overall stability check device, and theircomparison with the values of the same recommended by the IEC.The analysis of the results revealed:

a) tb.~ importance of maintaining a constant geometricalconfiguration while obtaining check source readings.

b) the necessity of reducing the instrument leakage.

Besides the C^ factors applicable for the exposurecalibrated BARC SSD hava been computed for the standardization ofphoton beam in the energy range from Co-60 to 30 MV. Theintervening parameters such as ths tufnol wall contribution todetector response, displacement correction factor have also beenmeasured at Co-60 photon energy.

4 . 9 . 2 • Me as tire me nt QJ£ the effectiveness of_ Boral Sleeve fornejiL1!?.'' P.hMiberjs end shie.ldijig. adequa.cy_ of lead housingmade for NAPP control chjtnnel

S.C. Krsra, P.S. Rao Suresh Rao and A.K. Mahant

In vifaw of the modification in the location ofcontrol/prat.K rice channel ion-chambers in NAPP the data on theabove paramet'.'i s required by NPB, has been obtained by theexperiments --•irried out in the shielding corner of APSARA, withreactor core a\ C position. The magnitude of the neutron fluxattenuation b/ three different types of boral sleeves has beenmeasured to be in the range 20 to 35%. The Lead shield gammadose attenuation factor has been determined to be better than450.

5. Servic e_s

The activities of the section are geared to serve the needsof nuclear industry, radiation therapy, research and radiologicalprotection for assuring reliable and accurate measurement ofionizing radiations. Radiation detector systems' calibration iscarried out as per the recorraendation of international electro

: 54 :

technical commission (IEC) and to the specifications ofOrganisation International de Metrology Legal (OIML). Variousservices provided to different units of DAB and otherinstitutions are listed in the Table 5.

Table 5: Services for the period 1982 - 1987

S.No

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

. Nature of Services

RadionuclideStandardization andIssue of Standards

Neutron Source and FluxMeasurement

Brachytherapy SourceStandardization.

Secondary StandardDosimeter and ClinicalDosimeter Calibration.

Neutron DetectorCalibration

Standard Gamma andNeutron Irradiations

Radiation MonitorCalibration

NationalIntercomparisons

Radioactive ContaminationMonitoring of Beta Gauges

Beta surface contaminationStandards

No.

200

50

60

103

138

491

197

3

50

15

Institution

BARC, Power Projects,Defence Labs andMedical Centres

BARC, IGCAR, and PowerProjects.

Medical Centres

Radiation TherapyCentre

BARC, IGCAR, PowerProject and ISRO.

BARC, IGCAR and ISRO.

Power Projects,Medical Centres andIndustry.

Nuclear MedicineCentres

Electronic Industries

NPB

: 55 :

PUBLICATIONS:

1. Inner wall contribution of an ion chamber at Co-60, P.S. Raoand A. Kannan, AMPI, Med. Phys. Bull. 7(1982) 217.

2. A simple modification to improve the energy dependence ofion-chamber survey meters, A. Kannan, V.W. Naik and P.N.M.R.Vijayam, Radiat. Prot. Dos. 3, (4) (1982) 223.

3. Air tissue *<juivalence and the utility of effective atomicnumber concept, A. Kannan and P.N.M.R. Vijayam, Bull.Radiat.Prot. 5, (1) (1982) 23.

4. Mass absorption coefficients and range of beta particles inBe, Al, Cu, Ag and Pb, R. Nathurant, I.S. Sundara Rao andM.K. Mehta, Pramana, 18 (1982) 121.

5. National intercomparison of activity measurements withIodine-131, P.K. Srivastava and Sunita Kamboj, BARCReport - 1149 (1982).

6. International intercomparison of Caesium-137, P.K. Srivastavaand Sunita Kamboj, 6th AMPI Conference, Srinagar, (1983).

7. Water absorbed dose measurement for 6 MV and 10 MV X-raybeams, P.N.M.R.Vijayam, K.D. Pushpangadan, S.B. Naik,I.S.S. Rao, AMPI Conference, Srinagar (1983).

8. Measurement of percentage depth dose values for orthovoltageX-Rays, Co-60 Gamma radiation and high energy X-rays,S.B. Naik, K.D. Pushpangadan, P.N.M.R. Vijayam, I.S.S.Rao, AMPI Conference, Srinagar, (1983).

9. Displacement correction at Co-60 for a SSD, A. Kannan andP.S. Rao, AMPI Med. Phys. Bull., 8 (1983) 29.

10. A Neutron Howitzer for calibration of neutron monitors atthermal energy, K.C. Pant, Suresh Rao, S.C. Misra andU.C. Gupta, Bull. Radiat. Prot. 6 (1983) 39.

11. A D-D neutron generator, measurement of its yield and neutronenergy, Suresh Rao, S.C. Misra and Suni'ca Kamboj, BARC-1205(1983).

12. Preparation and standardisation of beta surface sources forcalibration of contamination monitors, I.S. Sundara Rao,R.N. Vadiwala & R. Nathuram, Int. J. Appl. Radiat. Isot.34 (1983) 1398.

13. Experimental mass absorption coefficients for low energyphotons in Beryllium, Carbon, Aluminium, Silicon, Copperand Lead, R. Nathuram, I.S. Sundara Rao, M.K. Mehta, Ind.J. Phys. 58 A (1984) 300.

: 56 :

14. Elastic scattering cross-sections of electrons in detectormaterials, R. Nathuran and S.K. Gupta, Ind. J. Phys. 58 A(1984) 305.

15. Determination of C / for graphite walled reference chamber,A. Kannan, P.S. Rao and G. Subrahmanian, Strahlentherapie160 {1984) 35.

16. Production and measurement of 2.9 MeV neutrons, Suresh Rao,S.C. Misra, Sunita Kamboj and U.C. Gupta, Ind. J. Phys. 58A (1984) 260.

17. International interconparison of (d+t) neutron fluence andenergy using Niobium and Zirconium, Metrologia 20 (1984)49.

18. Second national intercomparison Kith Iodine-131, P.R.Srivastava, 7th AMPI Conference, Calcutta, (1984).

19. Primary standard for calibration of protection leveldosimeters, P.N.M.R. Vijayam and I.S. Sundara Rao, Bull, ofRadiat. Prot. 13th Annual IARP Conference, Bombay (1985).

20. Measurement of the Characteristics of Vanadium Self poweredneutron detectors, S.C. Misra, P.S. Rao, Suresh Rao andA.K. Mahant, BARC 1-850 (1985).

21. Neutron sensitivity of Vanadium self powered neutrondetectors, P.S. Rao and S.C. Misra, Nucl. Instr. & Meth. inPhys. Res., A 253 (1986) 57.

22. Calibration of radiation monitoring instruments in terms ofDose Equivalent Units, P.N.M.R. Vijayam, V.H. Naik, A.Kannan, AMPI ARCOMP Conference, (1986).

23. Calibration of brachytherapy sources, V.W. Naik, P.N.M.R.Vijayam, A. Kannan, P.S. Jadhavagaonkar, AMPI ARCOMPConference, (1986).

24. An Improved thermal neutron flux density standard for thecalibration of large detectors, U.V. Phadnis, B.K. Kamboj,M.G. Shahani and D. Sharma, NSRP-6, IGCAR, Kalpakkam,(1986) .

25. 14 MeV neutron flux measurements using Fe"» and itsinternational intercomparison, D. Sharma, M.G. Shahani, U.V.Phadnis, B.K. Kamboj and S.K. Sadavarte, NSRP-6, IGCAR,Kalpakkam, (1986).

26. Indium as a secondary standard for 14 MeV neutrons, B.K.Kamboj, M.G. Shahani, U.V. Phadnis and D. Sharma, NSRP-6,IGCAR, Kalpakkam, (1986).

: 57 :

27. Microprocessor based online data processing system forcoincidence set up, V.V. Shah, V. Singh , U.V. Phadnis andM.G. Shahani, All India Seminar on DigitalInstrumentation, P.S.G. College of Technology, Coin/Datore,(1986).

28. Precise measurement of the gamma to neutron ratio of a Am-Beneutron source using an improved manganese bath technique,B.K. Kamboj and M.G. Shahani, Nucl. Instr. and Meth. inPhys. Res., A 244 (1986), 513.

29. Third national intercomparison of activity measurements withIodine-131, P.K. Srivastava, H.K. Sahoo and P. Gangadharan,AMPI Conf., Trivandrum, (1987).

30. An intermediate energy neutron source, S. Kamboj, S.C.Misra, B.K. Kamboj, M.G. Shahani, U. C. Gupta, Nuclear Instr.Meth. in Phys. Ras. A 261 (1987) 601

31. Intercomparison of source emission rates (1978-84),Metrologia, 23, (1986 -87) 129.

32. Behaviour of G.M. type survey meters, P.N.M.R. .Vijayam, A.Kannan, P.S. Jadhavagaonkar,, 9th AMPI Med. Phys. Bull. 12 (4)(1987) 26.

33. Status of radiation standards for exposure maintained at DRP,S.B. Naik, K.N. Govinda Rajan, A.Kannan, AMPI Med. Phys.Bull. 12 (4), (1987) 9.

34. Limitation of a semiconductor dosimeter in patient dosemeasurements, A. Kannan, S.B. Naik, K.N. Govinda Rajan, AMPIMed. Phys. Bull. 12 (4) (1987).

35. International intercomparison of Californiura-252 neutronemission rates, M.G. Shahani, B.K. Kamboj, D. Sharma andU.V. Phadnis (Abstract), Proc. of 7th NSRP Symposium, Magalore(1987), 54.

36. Traceability in Radiation Metrology, S.C. Misra, AMPI Med.Phys. Bull. 12 (1) (1987) 29.

37. Extension of Burlin's general theory for dosimetry of photonsin low energy region, P.S. Rao and S.C. Misra. (Abstract),Vllth NSRP Symposium, Mangalore, (1987), 55.

38. Response of Brass-encapsulated CaFa TLD to high energyphotons, P.S. Rao, K.S.V. Nambi and P. Viswanathan, Bull.Radiat. Prot. 10 (82), (1987) 65.

39. Third National intercomparison of activity measurements withIodine-131/P.K. Srivastava, H.K. Sahoo and P. Gangadharan,AMPI Med. Phys. Bull, paper V 18, 12 (4), (1987) 11.

: 58 :

40. Photon attenuation coefficients for compound materials, R.Nathuran and M.K. Mehta (Abstract), VHth NSRP Symposium,Mangalore (1987). 56.

41. Range of 0 particles, R. Nathuram, G. Subrahmanian and S.R.Thontandarya, Ind. J. of Physv 61-A, (1987) 209.

42. Absorption of 0 particles in thin aluminium foils used assource mount in 4 n p counting, R. Nathuram and M.K. Mehta,Ind. J. of Physv 61-A, (1967) 499.

43. Use of system design kit for 4 n fl gamma coincidence set-up,V.V. Shah, V. Singh/U.V. Phadnis, M.G. Shahani and P.Gangadharan, All India Seminar on Microprocessor Applica-tion in Industry, Quality, Reliability and Availability ofElectronic System, Seminar Proceedings (1987) 1.

44. Mass attenuation coefficients of beta particles, R. Nathuram,G. Subrahmanian and S.R. Thontandarya, Physica (1987) inpress.

45. Photoelectric cross-section for 6-20 keV photons inBeryllium, Carbon, Magnesium, Aluminium, Silicon, Copper,Silver and Lead, R. Nathuram, I.S. Sundara Rao and M.K.Mehta, Phys. Rev. A 37 (12) (1988) 4978.

: 59 t

C. PERSONNEL MONITORING AND RESEARCH SECTION

S.J. Supe

1. Personnel monitoring service

Personnel monitoring service is rendered to radiationworkers in the country by this Section. Both, the film badgesand the thermoluminescence dosemeter badges, are being used. Theservice is generally being provided on monthly basis. Table 1.shows the number of radiation workers and institutions in variouscategories who availed the service during 1984 to 1986.

Table 1: Number of institutions and radiation workers inpersonnel monitoring service

Year

198419151986

Inst.

757582

D.A.E.lad.Vorks

133501261312032

Industriallast.

373402421

Rad.Horks

446348985255

MedicalInst. Rad.Vorks

1800 129541884 134802006 14292

Researchlost, tad

196205205

.Vorks

185511031)92

Inst

244425692714

Total. Had. Horks

326223286433571

Table 2 gives the average doses per person per year from 1984 to1986 for various categories.

Table 2 : Average doses per year per person (mRem)

Year

198419851986

DAE

472429456

IND

214227191

MED

677966

RES

232226

Total

250233240

During 1982 to 1986 rapid expansion of TLD personnelmonitoring programme has been achieved and 48% of the radiationworkers are now availing TLD badges. Table 3 gives the data onthe number of radiation workers availing TLD badges.

: 60 :

Table 3: The radiation workers availing TLD badges

Persons using TLDs Percentage of Total

DAEINDMEDRES

1128416462860390

94312020

Total 16180 48

For efficient and prompt reporting of the doses for theoutstation DAE units^six personnel monitoring laboratories usingTLDs have been started (Table 4). Some of these laboratoriesare also providing the service to the local non-DAE units.

Table 4: TLD personnel monitoring laboratories

PLACE

TAPSRAPSMAPSNFC,(Hyderabad]VEC,(Calcutta)INMAS

Inst

1166

)7

-(Defence Unit)TROMBAY

TOTAL

59

80

1.1 Excessive

DAE. Rad.Workers

110017341900567

612

-

5371

11284

Inst,

—--42

68

152

241

503

NON-DAE, Rad.Workexs

_--506

676

770

2944

4896

exposure investigations

Inst.

11648

75

152

300

583

TOTALRad.Workers

1100173419001073

1288

770

8315

16180

The dose recorded by the badges in excess of 1000 mrems(over a period of calender month) are treated as excessiveexposures and therefore communicated to the respectiveinstitutions on a priority basis. The excessive exposures ofDAE units are investigated by the committees appointed by therespective units as pesr guidelines provided by Safety ReviewCommittee (DAE). In case of Non-DAE units the excessiveexposures are investigated by a committee appointed by theDirector, BARC to decide genuineness of the exposures and

: 61 :

necessary further actions. On the basis of the investigationreports received from the institutions and other available datathe committee recommends necessary follow-up action. Ananalysis of the excessive exposures reported to the non-DAEunits which are investigated by the committee is shown in Table.5.

Table 5 : Analysis of the excessive exposures reported tonon-DAE institutions, 1984-86(1000 mrem in a calender month and higher)

Dose Range(Rent)

IND1984 MED

RES

Total

IND1985 MED

RES

Total

ZND1986 MED

RES

Total

11.99

109428

159

86500

136

60582

120

22.99

19108

37

11120

23

11171

29

34.99

580

13

1280

20

3140

17

59.99

111

12

13120

25

3190

22

>, 10

9154

28

10151

26

14132

29

Total

1438620

249

132971

230

91121

5

217

The persons whose badges recorded doses exceeding 10 reraand those suspected to have received high doses (10 rem andabove) are called to this Research Centre for medicalexamination and Chromosome Aberration Test. Table 6. givesanalysis of C.A. test conducted in collaboration with MedicalDivision of B.A.R.C.

Table 6

198419851986

Total

: Number of

MED

3916

28

persons

IND

4910

23

subjected to C.A.

RES

021

3

Test

Total

72027

54

s 62 *

1.2 A suggested modification in a commercially availablepersonnel monitoring film pack to improve itssuitability in high humidity areas.

R-V. Dhond, R.M. Worlikar, M.P. Sankaran and P.H. Patel

The Agfa-Gevaert films are preferred during monsoon as theyexhibit lesser latent image fading. However during monsoon whenrelative humidity is high the two films inside the film packtend to stick to one another and their physical seperation atthe time of processing becomes difficult resulting in damage ofthe films, which makes the dose estimation difficult.

The Agfa-Gevaert film pack was modified by introducing athin black paper of same size of film having thickness of 8.2mg/cm2 and sealing it to make it light proof. The modifiedfilms were stored in a humidity box having 90% relative humidityand 20°C temperature for a period of one month. In case of themodified film packs no sticking was observed. Furtherexperiments revealed that the response of the modified films tovarious doses of gamma and beta rays was almost same as thenormal films. Further, it was also seen that the pressurenumbering of the modified films could be done without anydifficulty.

The experiments showed that the proposed modification inthe commercially available Agfa-Gevaert personnel monitoringfilm pack will improve its usefulness for personnel monitoringprogramme during monsoon season.

1.3 Criticality accident dosimetry (CAD) badgeN.P.S.SiddhuA counting set up for beta and two gamma spectrometers (Nal

(Tl)) are kept in ready and calibrated condition for measurementof doses from CAD badges. Table 7 shows the number of CADbadges in use at various units of DAE.

Table 7. CAD badges used at various DAE UnitsName of Unit No. of CAD badges1. Radiometallurgy Division, Trombay 1402. P.P. , Trombay 523. Purnima, Trombay 294. C.S.O. 15. RAPS. Kota 156. PREFRE, Tarapur 1107. MAPS, Kalpakkam , 308. FBTR, Kalpakkam 209. N.F.C., Hyderabad 10

Total 407

: 63 :

2. Neutron monitoring

O.P. Massand

2.1. Fast neutron monitoring service.

The group conducts countrywide fast neutron monitoringservice using Kodak NTA nuclear emulsion. From 38 institutionsand 482 person*monitored in 1982, the service has grown to 47institutions and 876 persons during 1986. The service was madetwo monthly from May 1983 with improved moisture-proofpackaging. A total of 5600 Kodak NTA films packs were usedduring 1986.

2.2. Physical verification of »39Pu-Be neutron sources

O.P. Massand

Pu-Be neutron sources made by BARC are loaned out tovarious institutions all over the country and these are requiredto be verified physically -gvory year. During 1986, physicalverification of 36 Pu-ue sources in 24 institutions was carriedout.

2•3. Post-irradiation fading studies in Kodak NTA films

O.P. Massand, H.K.Kundu and P.K. Marathe

Post-irradiation latent image fading in Kodak NTA fastneutron personnel monitoring films is a problem of great concernparticularly in a tropical country like India. With theavailability of better moisture proofing materials in ourcountry, these studies were continued further. Using triplelaminate foils {Paper/Aluminum/Poly) for sealing the filmsdessicated in dry nitrogen no fading was observed for a periodof four months at 30°C and 76% R.H. Based on these studies theperiod of use of these films was extended thus reducing workloadand resulting in savings in foreign exchange.

2.4. Computed response of Kodak NTA to moderated neutron spectra

O.P. Massand and D. Singh

The energy response of the Kodak NTA dosimeter was computedto four radioactive neutron sources and twenty two sealedmoderated neutron spectra. This data provides usefulinformation regarding the correction factor to be applied whenthe Kodak NTA dosimeter is used in a particular known neutronenvironment.

: 64 t

2.5. Neutron measurements at 15 MV medical linear accelerator

O.P. Massand and U.B. Tripathi

Accelerators producing beams of 10 MV and above producesignificant quantities of photoneutronjfrom target, collimatorand beam flattening filter materials. Neutron measurementswere carried out with 15 MV Varian Clinac-20 linear acceleratorat Institute Rotary Cancer Hospital, A.I.I.M.S., New Delhi withIndium foils kept at the centre of a paraffin cylinder of 15 cmdiameter and 15 cm height. Indium foils activated as per thereaction l»sIn (n,x) ll6"In, emit photons of which one is 1.269MeV with a half-life of 54.2 minutes. Counting was done on aNal (Tl) single channel analyser. It was found that the doseequivalent of leakage neutrons to the X-ray dose at lm was 0.17%for this machine.

2.6. Computed response of CR-39 SSNTD to moderatedneutron spectra

O.P. Massand, M.P. Dhairyawan and P.K. Marathe

CR-39 solid state nuclear track detector shows a lot ofpromise for use as a neutron personnel monitor. The system hasbeen developed in our laboratory. Its energy response to twentythree selected neutron spectra was computed. Its neutron energythreshold is lower and it can be useful in the range 100 keV to10 MeV.

3. TLD personnel monitoring service

3.1 TLD badge service and evaluation of personnel doses

R.K. Kher and S.K. Gupta

On the basis of enormous general experience in the actualuse of TLD badge for personnel monitoring in nuclear reactor,Juel reprocessing plants, Waste management facilities and otherresearch units, the Division has planned and implementedambitious expansion programme over the period 1982-86 as shownin Tables 8 and 9. At present TLD monitoring service coversmore than 48% of radiation workers in our country. The presentTLD badge was basically designed as a beta-gamma badge. Thecapability of the present badge to estimate beta dose inpresence of both low and high energy gamma radiation was studiedand an evaluation procedure based on TL readouts of all thethree dosemeter discs of the badge is formulated. The presenceof different components of the radiation field is determined bythree checks during evaluation, based on relative TL readouts.A different approach is used for beta dose evaluation, which is

: 65 t

energy independent, in the beta energy range Baax = 1 MeV to 2.2MeV. from the pattern given by relative values of TL readouts ofthe three discs, nature of radiation could generally be judgedwhich helps in detection of contamination and investigation ofover-exposure cases. The badge could also be relied on todetect high background in working area. Its characteristic ofalmost no fading of TL response over the period of one to threemonths and less than 10% fading over the period of one year isimportant in optimization of efforts and affective control ofradiation doses in country wide personnel monitoring programme.Results of intercomparison studies among TLD badge, -film badgeand Quartz fibre pocket chambers in field conditions for nuclearreactor environment and TLD badge and film badge for medicalradiation workers have indicated good agreement.

Table 8: Expansion of TLD service at Trombay (1982-1986)at a glance

Year Inst. PersonsOERCases

UrgentProcessing

New TLD u n i t sCommssioned

82-8383-8484-8585-86

5556565

5700600060006000

5080

12415

200180350250

RAPS,

—MAPSINMAS, NFC

VEC

Table 9: Details of countrytide TLD service as OD January 1, 19t7

PlaceDIE Medical Industrial Research Total

Inst. Korkers Inst. forkers Inst. Korkers Inst. lorkers Inst. Borkers

TroiiayHyderabadCalcuttaTAPSMAPSRAPSDelhi

64i7161-

5451567612

110019001734

1672125---

147

1596230284---

700

591134---

1197105324----

15109----

15117168----

3054875161

147

138510731288110019001734700

Total 85 11354 360 2810104 1626 34 390 583 16180

3.2 On the design of TLD badge and calibration setup forpersonnel monitoring

R.K. Kher, H.R.S.M. Achar, K.L. Popli and A.V. Dere

Effects of backscatter photons and buildup electrons for variousenergies from 29 keV to 120 keV, in the design of TLD badge isstudied. The backscatter photons which essentially are of low energy,

: 66 :

affect the TL response, thereby resulting in uncertainty in doseassessment. It is recommended that for improved design of the TLDbadge, the TLD card should be closely packed in the cassette havingmettalic filters. To assess the contribution of bremsstrahlunggenerated in the metalic filters, simple computations have been done.The estimated contribution due to bremsstrahlung photons byattenuation of incident beta rays in the metallic filters (Al + Cu) isaround 0.65% of beta dose which is negligible and does not require anycorrection in beta-gamma dose estimation.

IAEA stipulates that accuracy of calibration for personnelmonitoring for energies 200 keV to 2 MeV must be within 5% . Thedesign of the calibration setup for high Z personnel monitors(CaSCU :Dy and Film) was studied for *°Co and l3TCs gamma sources forvarious heights (from 30 cm to 150 cm) from concrete floor usingspherical graphite chamber. The measurements also have been done byplacing the dosemeters on calibration jigs made up of wood and (steel+ wood) at a height of 80 cm from floor. It was found that wooden jigshows over response by 8% to 10% and (steel + wood) jig show 30% to33% over response.

3• 3 Reusability of TL dosemeters for personnel.monitoring

R.K. Kher and K.L. Popli

Reusability and uniform sensitivity of TL dosemeters (whicheliminates individual calibration) is a unique feature of our TLDsystem. Effects of change in optical density and deformation of discswhich lead to variation in sensitivity were studied. It was foundthat after 20 cycles of use, spread (S.D.) in sensitivity was ±18%.Treatment at 400°C -lh in air oven improves optical properties (andhence sensitivity). Further studies on treated discs show that spread(S-D) in sensitivity remains constant (i.e. 8%) for further20 cyclesof use. Glow curve profiles were studied to assess effect ofdeformation leading to poor contact with heating element. Thesestudies have shown that TL dosemeters could be used upto 100 cycles ifa different annealing procedure is adopted which will minimizedeformation.

3.4 Methods of assessment of individual dose and collective doseto transport workers and members of public resultingfrom radioactive shipment (IAEA RC No. 2740/RBj_

K.G. Vohra, G. Subrahmanian, R.K. Kher, A.N. Nandakumarand R.K. Iyer (Isotope Division)

The study carried out in BARC relates to wlnods of assessment ofindividual and collective doses co transport •> irkers and members ofpublic, incidental to the carriage of radioactive material. On thebasis of observed work practice, individual doses of selected personswere computed. The estimated doses agraed within 25% with the

: 67 :

measured doses using TLD personnel monitoring badges. Collectivedoses to the public were evaluated by computation on the basis ofmeasured exposure rate at locations around the vehicle carryingradioactive cargo and population occupancy at the same locations.

The personnel doses were also evaluated with reference to thetotal transport index handled by transport workers at the air port,yielding results consistent with those reported elsewhere by earlierresearchers. The estimated annual collective dose to the transportworkers is 14.2 person-mSv (i.e. 1.42 person-rem) for the movement ofabout 12,000 packages of radioactive materials and collective dose forthe members of the public is estimated as 0.1 person-Sv (i.e. 10person-rem) in our country.

3.5 Dose estimates uaing DRP criticality badge in IAEA/ORNLinternational intercomparison study on .nu. cigar..Ji^cidentdosimetrv (NAD-1983)

R.K. Kher and N.P.S. Siddhu

DRP participated in the above study convened by IAEA and ORNLjointly at ORNL, Oak Ridge, Tennessee, USA during Sept. 12/16, 1983.DRP had participated in earlier NAD intercomparison studies at CRACfacility, Valdue, France (1970); HPRR facility, Oak Ridge, USA (1971);RB-2, Vinca, Yugoslavia (1973) and Viper facility, Harwell, UK (1975).Criticality accident dosimetry badge system of DRP/BARC was used formeasurements of neutron and gamma doses in (a) free air and (b) onBOMAB phantom at a distance of 3 metres from the core of HPRR reactorin the three experiments with neutron spectrum (i) Unshielded, (ii)shielded by 13 cm steel and (iii) shielded by 20 cm concrete.

Measurements on activation detectors (Au, Cu, In & S) were madeimmediately after each experiment at DOSAR facility at ORNL. Table 10shows the results of fluence estimation in the three experiments infree air measurements. Estimates of neutron dose (KERMA) and gammadose are obtained using appropriate dose conversion factors from thedata compiled by IAEA and compared with reference dosimetry data forHPRR. The agreement is good.

Overall, about 83% of all neutron measurements by participantssatisfied regulatory standards relative to reference values but only39% for gamma measurements.

: 68 i

Table 10: Results from measurements using DRP criticality badge systemand comparison with reference doaimetry data

Experiment Number

Yield (fission)Neutron fluence

Thermal0.4 eV to 100 KeV

> 0.1 MeV> 1.0 MeV> 2.5 MeV

Total fluence(Reference)

I

9.37

0.799.14

12.86.462.6522.79(18.64)

Maxwellian Past Spectrumo (In)/ a (S)

EIntermediate Energyo (Au)/o (Cu)

aIn air stationNeutron dose KERMA

(Reference)Gamma dose

(Reference)On phantomNeutron dose KERMA

(Reference)Gamma dose

(Reference)

2.82.1

Range71.519.5

305.0(375.0)44.0(62.0)

477.0(430.0)96.0

(105.0)

II

7.86

0.43.15.842.220.389.34(9.48)

5.11.2

117.517.0

121.0(137.0)13.0(18.0)

175.0(141.0)30.0(42.0)

3.6. Radiation transport calculation

S.K. Gupta

(a) Electron : Electron Monte Carlo program

III

5.89

1.11.292.891.030.155.26(5.89)

7.01.0

260.07.0

58.0(51.0)15.0(20.0)

89.0(59.0)27.0(33.0)

based on

lx.10")[x 10'°}

[x lo-3]

trad]

[rad]

trad]

[rad]

conventionalcondensed random walk model has been fully developed. Electron singleelastic scattering cross-sections were computed using Mott'srelativistic theory. These were incorporated in Gondsmit-Saundersontheory of multiple scattering to obtain multiple scatteringdistribution at the end of pre-determined path length of the electrontrajectory. The inelastic collisions were treated under continuousslowing down approximation.

Further, an alternate approach for the electron transport hasbeen fully developed. In this approach, we have generated and usedpseudo-reduced single elastic and inelastic scattering cross-sections.The electron is thus followed collision by collision. Our approach,in addition to simplicity, has distinct advantage over conventional

i 69 t

Monte Carlo scheme particularly for calculations at interface andinclusion of Bremsstrahlung collisions.

The transmission and albedo facors for 1 and 0.5 MeV electronsnormally incident on materials of low and high atomic number (Al & Cu)have been obtained and compared with earlier results. The agreementis reasonably good.

(b) Gamma; Gamma-ray Monte Carlo program has also been fullydeveloped. The calculations have been done for the distribution ofabsorbed-dose in ICRU sphere for a broad parallel beam, a pointisotropic source and an isotropic flux and energies below 1 MeV.Special Monte Carlo techniques have been adopted to increase theefficiency of our calculations. The results of our calculations agreewell with available results in the literature.

3.7 Evaluation of ICRP person dose and risk estimates for reactorpersonnel and medical radiation workers

R.K. Kher, M.M. Adtani and K.S. Shenoy

For evaluation of effective dose equivalent for workers inwuclear power stations, from chest dose,a factor of 0.86 is suggstedon the basis of measurements on mix-D phantom. From the average ofcollective dose equivalent for 15 years for various categories ofworkers, risk estimates were obtained and compared with risk involvedfor the workers in various industries. It is concluded that theworkers in nuclear power Stations are more safe than workers in otherindustries.

It is also shown that it is practicable to convert the measuredsurface dose as estimated from personnel monitoring system to theeffective dose equivalent for medical radiation workers. An averagevalue of correction fetor for all medical institutions is 0.59. Riskestimates for medical and industrial radiation workers are alsoobtained.

3.8 Personnel dose distribution analysis

R.K. Kher and K.S. Shenoy

Analysis of occupational annual exposure data of different groupsof radiation workers is expected to follow lognormal distribution atleast in the lower dose range upto 2 rem. From parametric studies ofUNSCEAR reference distribution (1977) (withdrawn after 1983)difficulties in its use for comparison are analysed. Dosedistributions for industrial radiography workers or workers of |>uclearfacilities deviate considerably from lognormal distribution. Hybridlog-normal distribution is shown to be more appropriate for study ofsuch distributions. The parameters of distribution and numericalevaluation of relevant statistical quantities are obtained for dose

: 70 i

data for workers in industrial radiography and nuclear power stationsfor a few years.

3.9 Depth dose measurements using TL dosimeters for *0Co andMV photon beams

R.K. Kher, K.L. Popli, V.K. Nelson (DRP Trainee)

The suitability studies of two TL systems viz. CaSO«:Dy PTFEdiscs, LiF (100) for the measurement of central axis depth dose of Co-60 and megavoltage photon beams were done. As the CaSO«:Dy PTFE discsare locally made the effect of energy dependence on these discs tohigh energy photons was also studied. The result obtained by these twoTL systems viz.TLD-100 and CaSO<:Dy were found to be reproducible andwithin 1.5* & 1.3% respectively for60Co and 10 MV X-raya. The resultswere found to be within ±4% when compared with BJR supplement 11values.

3.10 Use of TLD and film badga for medical workers - a comparativestudy

R.K. Kher, A.V. Dere and S.J. Supe

Majority of radiation workers in our country are engaged inmedical diagnostic X-ray instituions. Due to many advantages offeredby TLD system over the presently used film badge monitoring system theTLD system has been introduced in about 130 institutions. Acomparative study of the doses shows that the average dose recordedper radiation worker by TLD is 21.1 mrem for six months whereas forfilms it is 11.6 mrem for previous 6 months of the same year. Nearly65% of the TLD cards recording non-zero doses showed clear pattern ofexposure to x-rays.

4. Dose records and statistics

S.K. Gupta

One SN/23 computer with 3 terminals and two personal computerswith one dot matrix printer are available in this group. Theactivities of the Group are given below:

I. (a) Maintaining personnel montoring data

(b) Monthly and annual reports for personnel doses.

II. Developed data base for radioisotopes (open/sealed) handled byvarious institutions. Data received through packing notes fromIsotope Group was used for this purpose.III. Details of the candidates undergoing various training courseswere compiled.

: 71 :

IV. Software development for data tranfer from 8 inch floppy disksused in DCM/HCL/NELCO etc. workstations into industry standardmagnetic tape or IBM-PC compatable floppy disks. Such a facility isavailable only in this group in BARC and is being used by users fromother divisions in BARC and DAE units.V. Associated with a project, in Instrumentation Section, to recordfilm's optical density/TLD reading directly to personal computer.VI Compilation & preparation of quarterly report of the safetyrelated activities.VII. Nuclear medicine data (85 institutions).

5. Personnel monitoring and TLD development work

5.1 Production of TLD discs

R.C. Bhatt

CaSO«:Dy teflon TLD discs developed in the Division have foundwide applications in personnel monitoring. At present about 16,000radiation workers are being monitored by using the TLD badge systemdeveloped by the TLD development group. For producing CaSO< :Dy TLDdiscs, the CaSO«:Dy phosphor powder(received from Chemistry Divisionof BARC) is ground to below 7 5 micron grain size and its TLsensitivity is checked against a standard batch of CaSCu :Dy. Thepresent method of production of TLD discs by us involves mixing ofCaSCu :Dy powder and Teflon powder in a weight ratio of 1:3, weighingsamples of 280 mg each from the mixture, cold-pressing of discs of 280mg each from the samples, acetone cleaning of the cold-pressed discs,and moulding (at 400*C) of cold-pressed TLD discs. We have alsoproduced 64000 TLD discs with the help of a West German Teflonprocessing Company. After checking their TL sensitivity these TLDdiscs (German made) were separated into two lots, one having a TLsensitivity of 94% compared to the DRP produced discs (made byindividual cold compaction and subsequent annealing at 400°C, lh) andthe other lot having a TL sensitivity of 78% of the DRP discs. Bothof these lots will be used for personnel monitoring. Large scaleproduction of the Teflon TLD discs is being tried from mouldedCaSCu :Dy Teflon rods. This is being done with the help of a localTeflon processing company. The Company has already supplied us 15000TLD discs with satisfactory TL characteristics. No appreciable changein the sensitivity of the TLD discs used in personnel monitoring hasbeen observed even after 40 cycles of reuse under laboratoryconditions. However, in field conditions, the TLD discs have showndiscolouration and buckling even after 10 cycles of reuse. It hasbeen possible to remove this dis colouration and buckling of the discspartially by annealing them at 400°C, lh.

The performance of CaSO«:Dy teflon discs for environmentaldosimetry was tested in a series of International Intercomparisons ofEnvironmental Dosimeters and found to be highly satisfactory.

: 72 :

5.2 Effect of doping with monovalent cation impurities on _thethermoluTainescence response of CasO< :Dy phosphor

Bhuwan Chandra, S.S. Shinde, A.R. Lakshmanan aiy2 R.C. Bhatt

Doping of CaSO«:Dy TLD phosphor with either Li* or Na* (as chargecompensators) was found to reduce the peak ho-1' ;hts of 225° C as well as375°C TL peaks; the reduction being concentration dependent. Theremoval of Ca2 • vacancies (generated due to Dy3 • doping) in CaSO«:Dyby the addition of Li4 (or Na*) destroys the traps corresponding todosimetry peak (225°C) as well as high temperature TL peak (375°C).This result agrees with the earlier suggestion that S042- radicalsclosely associated with Ca*• vacancies act as hole traps for 225°Cpeak.

5.3 Annealing and reusability characteristics of LiF (Mq,Cu,P) andLiF(Mq,Cu) TLD phosphors

Bhuwan Chandra, A.R. Lakshmanan, S.S. Shinde and R.C. Bhatt

The main dosimetric peak of LiF (Mg,Cu,P) phosphor is 1.4 and 38times more intense than that of CaSO*:Dy and LiP TLD-100,respectively. Its TL sensitivity is strongly dependent on temperatureand duration of annealing. However, by using a suitable TL readoutcycle and post-annealing treatment at 250°C it was possible to use thephosphor for at least 10 reading cycles.

Due to its tissue equivalence, extended linearity, and high TLsensitivity (3.3 tiroes of LiF TLD-100), LiF (Mg, Cu) is useful inMedical Physics for diagnostic as well as for therapeuticapplications.

5.4 Effect of temperature of irradiation, photon energy dependenceand dose reestimation characteristics of LiF TLD-100

Bhuwan Chandra, A.R. Lakshmanan and R.C. Bhatt

A strong dependence of the intensity of the thermoluminescenceoutput of peaks 5(208«C), 7(255»C) and 10(422°C) on temperature ofirradiations was observed in LiF TLD-100 in the dose range 1.7 x 10*to 2.5 x 103Gy. Photon energy dependence of TL peaks 4,5,6 and 7 invirgin and 145° - 24h pretreated LiF TLD-100 was studied in the range29-1257 keV. It was observed that only peak 7 shows higher energydependence as compared to other TL peaks thereby indicating that peak7 corresponds to 2-hit traps.

UV/thermal anneal sensitized samples can be used to measure lowdoses of the order of 0.1 mGy due to absence of interferring hightemperature peaks. However, they canot be used for re-estimation oflow doses using the standard PTTL technique because of high

: 73 :

re-estimation TL background.

5.5 Development of an X-ray badge

A.S. Pradhan, K.G. Vohra and R.C. Bhatt

A TLD badge was developed for radiation workers encountering Xand gamma rays in medical and industrial installations where the useof beta-ray sources can be ruled out. By taking into account thereadouts of TLD discs under metal filter and under open window thephoton energjjfclependence was brought down to within ± 15% in the rangefrom 25 keV to 1.25 MeV, and the angular dependence within ± 30%.

5.6 Development of LiaBiOTiCu TLD phosphor

A.S. Pradhan, R.C. Bhatt and K.G. Vohra

The preparation parameters of sensitive and tissue equivalentLisB«O7:Cu TLD phosphor were studied. A material of TL sensitivitycomparable with that available commercially was prepared and itscharacteristics were studied.

5.7 UV and gamma ray sensitivity of CaFt baaed TLDs

A.S. Pradhan and R.C. Bhatt

Heat treatment at temperatures above 500°C (in air) was found tochange the TL sensitivity of these TLDs. An increase in UVsensitivity was found to be due to the production of oxide at the TLDgrain surface whereas the reduction in gamma ray sensitivity wasattributed to the change in the defect complexes responsible for theTL.

5.8 Photo-transfer in CaSO<;Dy TLD

A.S. Pradhan and R.C. Bhatt

Photo-transfer thermoluminescence (PTTL) has been found to behighly dependent on gamma ray dose. It was concluded that PTTLoriginates not only from the residual TL traps but also from the otherradiation induced nonluminescent centres.

5.9 Fast neutron sensitivity of TLDs

A.S. Pradhan

Fast neutron sensitivity of several TLDs was studied. Based onthe difference in the LET dependences of glow peaks, a two peak methodwas developed for simultaneous measurement of gamma-ray and neutrondoses in mixed fields.

: 74 :

5.10 Radiation dosiroetry with thermoluminescent materials

A.R. Lakshmanan, Bhuwan Chandra and R.C. Bhatt

The low and high temperature response of CaSO«:Dy, CaF»:Tm andLiF:Mg, Ti to X and gamma radiations were studied. The peak heightratio of CaFz:Tm and LiF:Mg, Ti were found to depend on the LET of theradiation. The LET as well as the dose of high LET radiations couldbe estimated using a single sampe of CaFs:Tm. Detailed studies on thevarious radiation dosimetric characteristics of Li»B«O7:Cu (a newlydeveloped tissue equivalent phosphor) were made. The mechanism ofnonlinearity on the response characteristics of several TL materialswas studied. Dependence of their TL sensitivity on the temperature ofirradiation was also studied.

5-11 A comparative study of some CaSO< .'phosphors

A.R. Lakshmanan, S.S. Shinde and R.C. Bhatt

CaSCu doped with Ti, Zr, Dy, Mn, (Pb,Mn), (Ag, Mn), (Zr, Mn),and (Zr, Dy) were made and their TL characteristics compared. Ofthese, only Dy gives high TL sensitivity coupled with a good thermalstability.

5.12 Basic studies on the TL in LiFzMg, Ti and LiF:Ti

A.R. Lakshmanan, Bhuwan Chandra and R.C. Bhatt

In LiFrMg, Ti, gamma irradiation at 77K (liquid Nitrogentemperature) reduces the TL intensities of peak 7 (260°C) and 10(450°C) drastically, but peak 5 (200°C) remains nearly similar to thatafter irradiation at 25°C. This implies that : (1) duringirradiation, interstitial migration is involved in the formation oftraps giving rise to peaks 7 and 10 and (2) *lectron-hole model hassome bearing only on the TL process of peaks occurring below 200°C.The TL process of peak 10 has been explained well by the mobileinterstitial model.

Since the main TL glow peak (250°C) and F band (250 nm) opticalabsorption in LiF:Ti are found to be nearly absent after gammairradiation at 77K, we propose that this peak results frominterstitial vacancy recombination during I7centre annihilation.

5.13.Semiempirical analysis of nonlinear thermoiuminescence effectsand a new TL model : Competing TL trap distributions model

J.K. Srivastava and S.J. Supe

None of the existing TL models explain the physical mechanism ofnonlinear (or linear) TL effects like complex dose and LET dependent

: 75 :

variations in glow curve shapes of virgin, sensitised and radiationdamaged TL phosphors along with their nonlinear (linear) TL resposecharacteristics. Following a detailed differential TL analysis of TLphenomenology of CaSO*:Dy under diverse energy transfer conditions, anew TL model has been proposed. The elements of the model, discussedin detail in physica status solidi (a), Vol. 92, pp 573-588 (1985),were found to be physically compatible with existing statistic-kineticconcepts and multiphonon emission (MPE) transition theories. Theessence of the model, which attributes preferential capture reactionof deeper traps, in terms of generalised coordinate versus potentialenergy schematic is given below:

A trap subsequent to capture of a carrier tends to reach itsground state with multiphonon emission processes. When a distributionexists, the trapping system may involve all the traps simultaneously,but with a preferential nonradiative MPE capture transition to theground state of lower, mostly unoccupied trapping levels (deepertraps) with a higher capture coefficient as compared to that ofcorresponding transition to shallower traps.

Being of unified and generalised nature, the model successfullyexplains LET and dose dependent non-linear TL effects of CaSO«:Dy andthat of other common phosphors like CaF*:Dy, LiF(TLD-lOO), LiaB«07:Mn;L11B4O7 :Cu etc.

5.14 Effect of radiation quality on radiation damage ofthermoluminescence of CaSCU :Dv - Mechanism of radiationdamage of TL

J.K. Srivastava and S.J. Supe

From investigations on CaSO*:Dy, it is found that glow curveshape and TL response characteistics show conspicuous 'residualeffects', both reversible and irreversible for gamma radiation. Thereversible effects, attributed to radiation induced TL sensitisationcompletely disappear only at temperatures >, 650° C. However for gammadoses above 100 Gy, irreversible effects, attributed to permanentradiation damage of TL, are also noted. In sharp contrast, alpharadiation shows only reversible effects irrespective of the doselevels, including very high doses such as 10°Gy. The study veryconspicuously demonstrated that radiation damage of TL manifestspreferentially via deeper traps. The competing TL trep distributionmodel accounts both the mechanisms of radiation sensitisation andradiation damage of TL.

The study highlights that phosphor samples previously unsuitablefor reuse due to high dose could be reused following annealing at650°C - 0.5 hrs; instead of 400°C, without any loss or change of TLsensitivity.

The study also suggests that using a combination of high gamma

: 76 :

dose and high temperature treatment, TL characteristics of a 'poor'batch of CaS04:Dy, which show large shoulders in high temperatureregion of its glow curve, could be substantially improved.

5.15 Trapping parameters of CaSO«:Dy

J.K. Srivastava and S.J. Supe

Trap distribution analysis of CaSO«:Dy shows that its TL involved21 groups with quasicontinuous distribution of activation energiesfrom 1.15 to 2.39 eV in 70 - 470° C region. The trap spectrum revealsa predominant 1.40 eV trap group linked to 220°C main dosimetric peak.The frequency factors range from 8 x 101 * to 2 x 1016 s-l .

5.16 Dosimetric technique for reduced nonlinearity of TL responseof CaSO< :Dy

J.K. Srivastava and S.J. Supe

To overcome or reduce the problem of TL supralinearity,encountered beyond 0.5 to 1 Gy of low LET radiations, a simpledosimetric technique is suggested. It consists in utilising TL ofonly lower temperature regions of glow curve. An appreciablereduction of supralinearity and a many fold increase in range oflinearity {about 10 fold) is obtained while measuring TL of CaSO<:Dyonly upto 220°C, its peak temperature. The technique is based onreduction of capture reaction mechanism of shallower traps.

5.17 Effect of radiation quality on TL fading of CaSCU ;Dv in high:lose region

J.K. Srivastava and S.J. Supe

Loss of TL signal during storage of CaSO« :Dy TL dosimeters hasbeen investigated for various radiation qualities and quantities (LETand absorbed dose). For a given radiation quality, TL fading decreaseswith increase in dose reaching a minimum followed by its gradualincrease. Such a dose dependence of TL fading decreases with increasein LET.

5.18 Thermoluminescence characterisation of LiF(Mq,Cu,P) phosphor

J.K. Srivastava and S.J. Supe

The newly developed LiF(Mg, Cu, P) phosphor (China made), atissue equivalent material with higher TL sensitivity than CaSOi:Dy,was investigated for its trap distribution characteristics and unusualbut favourable linear TL behaviour. The analysis shows a spread ofactivation energies from 1.2 - 2.38 eV in 9 trap groups distributedconspicuously unlike that of other common phosphors. The main peak at215°C has been related to very deep traps of 2.35, 2.38 eV. The other

: 77 t

constituent peaks both at lower or higher temperatures haveconsiderably lower activation energies. ' he competing TL trapdistribution model, in terms of such conspicuous trappingcharacteristics, very reasonably explains the 'unique' linear TLbehaviour of this phosphor.

6. Population exposure studies

6.1 Studies on time dose relationships for multiple dailyfracionation treatment regimes at radiotherapy

S.J. Supe, J.B. Sasane and J.G.R. Solomon

The time dose models formulated in various concepts like CRE,TDF, TSD, ERD were applied to patient data from Kasturba MedicalCollege Hospital, Manipal on Multiple daily fractionation treatment(MDF) regimes to check their validity or otherwise for MDF. Time Dosemodels were suitably modified for CRE and TSD concepts for 2F/day and3F/day regimes. Studies were continued for Linear Quadratic model inERD concept.

6.2 Determination of radiation exposure to patients and personnelduring various medical diagnostic/radiotherapeutic proceduresusing CaSO«;Dv TL dosimeters

S.J. Supe and J.B. Sasane

This has been done/being done for the following procedures fr.oavarious institutions.(i) Diagnostic X-ray examinations of paediatric patients at K.G.Medical College, Lucknow: In this organ doses for eye, thyroid, chestand gonads for peadiatric patients undergoing various radiologicalexamination were estimated.(ii) Radiological procedure duing percutaneous Nephro Lithotomy (PCNL)at Bombay Hospital: For the procedure patient doses at various sitesand personnel doses for hands, eyes, thyroid and gonads were measured.(iii) Scattered radiation doses to critical organs during variousradiotherapeutic techniques were measured for patients at RajkotCancer Society Hospital, Rajkot.(iv) Doses to radiotherapy technicians during their normal handling ofpatients during treatment at V.N. Cancer Hospital, Coimbatore weremeasured.(v) Rectal dosimetry in Gynecological Brachytherapy was carried outon 30 patients at Aurangabad Medical College Hospital, Aurangabad.(vi) Bone and soft tissue interface dosimetry was conducted on thighmix-D phantom for CO-60 beam with and without steel nail in thephantom, at Christian Medical College and Brown Memorial Hospital,Ludhiana.

: 78 t

6.3 Volume correction factor for TDF and CRE conceptfor brachytherapy

S.J. Supe, J.B. Sasane and M.K. Gupta

This was estimated from Peterson's Clinical data aboutinterstitial implants with Ra-226. A table of volume corrected TDFfor various volumes and dose rates for continuous irradiation wasprepared for ready use.

6.4 Genetic risk during radiotherapeutic treatment of cancer ofthe penis

S.J. Supe and J.B. Sasane

This was evaluated by measuring radiation doses to gonads byactually simulating the conditions of treatment on phantom.Measurement were made by using LiF (TLD-700) dosimeters for open beam,beam with breast cone, beam with gonadaljshield and beam with breastcone in conjunction with gonadal shield.

6•5 Surface dose and build UP measurements for variousCo-60 teletherapy units

J.B. Sasane and P.S. Viswanathan

These measurements were carried out using LiF TLD dosimeters.Measurements were also carried out using flat X-ray chamber.

6.6 Comparison of treatment plans for early and late stages ofCa-Cervix

S.J. Supe and J.B. Sasane

The comparison was made by obtaining isoeffect lines for the twotechniques using the concepts of CRB, TDF and TSD.

6.7 Calibration of opthalmic Sr-90 applicator

S.J. Supe, J.B. Sasane and S.M. Rao

Calibration was carried out for opthalmic Sr-90 applicator ofLMTG Hospital, Sion.

: 79 tPUBLICATIONS

PM and TLD development Group

1. Personnel dosimetry in criticality accidents, R.C.Bhatt, NuclearIndia, 20 (10) (1982) 1.

2. Development of Li2B<O7:Cu phosphor for radiationdosimetry, A.S. Pradhan, R.C. Bhatt and K.G. Vohra, Bull, of Rad.Prot. 5 (1982) 43.

3. Response of low and high Z TL phosphors and CaSO<:Dy Teflondiscs in phantom to *°Co gamma rays, A.S.Pradhan, S.Balachandran and R.C. Bhatt, Bull.Rad. Prot. 5 (1982) 175.

4. X and gamma ray response of TLD badge based on CaSCu :Dy Teflondiscs, K.G. Vohra, A.S. Pradhan and R.C. Bhatt, Health Phys. 43(1982) 391.An environmental gamma ray dosimeter using CaSCU :Dy Teflon TLDdiscs, K.G. Vohra, R.C. Bhatt, Bhuwan Chandra, A.S. Pradhan andA.R. Lakshmanan, Health Phys. 42 (1982) 217.Response of sensitized CaSO*:Dy phosphor and phosphor embeddedTeflon TLD discs to X and gamma rays, A.S. Pradhan and R.C.Bhatt, Radiat. Prot. Dosim.2 (1982) 23.Some preparation parameters of LisBiOriCu TLD phosphor,k.C. Pradhan, K.G. Vohra and R.C. Bhatt, Radiocheir. Radioanal.Letters 52 (1982) 103.Response of different Z.tf-.TLDs for in-phantom dosimetry of " C oirradiations, A.S. Pradhan, S. Balachandran and R.C. Bhatt,Nucl. Instrum. Methods, 204 (1982) 251.Response of CaSO«:Dy Teflon discs to diagnostic X-rays, A.S.Pradhan and R.C. Bhatt, AMPI Med. Phys. Bull. 7 (1982) 211.The low and high temperature response of CaSO<:Dy dosimeters toX and gamma rays, A.R. Lakshmanan and R.C. Bhatt, Int. J. Appl.Radiat. and Isotopes, 33 (1982) 464.Thermoluminescence response characteristics of CaF2:Tm to X andgamma radiations-evidence for the presence of 2-hit traps, A.R.Lakshmanan, Bhuwan Chandra and R.C. Bhatt, Rad. Prot. Dosim. 2(1982) 13.On the role of Z centres and competing nonluminescent centres inthe sensitization and supralinearity mechanism in LiF TLD-100,A.R.Lakshmanan, Bhuwan Chandra and R.C. Bhatt, J. Phys. D.Applied Phys. 15 (1982) 150.High level gamma dosimetry using high temperature TL peaks inLiF (TLD-100),Bhuwan Chandra, A.R. Lakshmanan and R.C. Bhatt,Int. J. Appl. Radiat. and Isotopes, 33 (1982) 679.Dependence of thermoluminescence sensitivity on temperature ofirradiation in LiF(TLD-100) phosphor, Bhuwan Chandra, A.R.Lakshmanan and R.C. Bhatt, J. Phys. D. Appl.Phys. 15 (1982)1803.Further studies on the radiation dosimetry characteristics ofthermoluminescent Li2B^O7:Cu phosphor, A.R. Lakshmanan,Bhuwan Chandra and R.C. Bhatt, Rad. Prot. Dosim. 2(1982) 231.

: 80

16. Low dose measurements with CaSO*:Dy Teflon thermoluminescentdosimeters, A.R. Lakshmanan and R.C. Bhatt, Int. J. Appl.Radioisotopes, 33 (1982) 707.

17. Estimation of quality and intensity of low energy photonradiation using a single sample of CaFs:Tm, A.R. Lakshmanan,Bhuwan Chandra and R.C. Bhatt, Int. J. Appl. Radiat. andIsot. 33 (1982) 703.

18. Annealing and re-usability characteristics of LiF (Mg, Cu, P)TLD phosphors, Bhuwan Chandra, A.R. Lakshmanan, R.C. Bhatt andK.G. Vohra, Radiat. Prot. Dosim. 3 (1982) 161.

19. Mechanism of nonlinearity in the response characteristics ofthermoluminescent dosimeters : A further comment, A.R.Lakshmanan, J. Phys. D. Appl. Phys. 15 (1982) L 189.

20. A review on the role of thermoluminescent dosimeters on fastneutron personnel dosimetry, A.R. Lakehmanan, Nucl. Tracks, 6(1982) 59.

21. Photon energy dependence of various TL peaks in LiF (TLD-100),Bhuwan Chandra, A.R. Lakshmanan and R.C. Bhatt, Int. J. Appl.Radiat. Isot, 33 (1982) 1399.

22. Thermoluminescence sensitivity of CaSO« :Dy phospnor dosimeter-effect of temperature, S.S. Shinde and R.C. Bhatt, FifthConference on Medical Physics GKNM Hospital, Coimbatore,Jan.(1982). AMPI Bulletin, 7 (1982), Abstract No. C-23.

23. Dosimetric characteristics of thermoluminescent LiiB«O7:Cuphosphor, A.R. Lakshmanan, Bhuwan Chandra and R.C. Bhatt, IbidAbstract No. C^25.

24. Thermoluminescence in personnel monitoring and response ofCaSO<:Dy teflon discs to diagnostic X-rays, A.S. Pradhan and R.C.Bhatt, Ibid. C-5 (Abstract).

25. High level gamma dosimetry using high temperature TL peaks inLiF (TLD-100), Bhuwan Chandra, A.R. Lakshmanan and R.C. Bhatt.Ninth Annual IARP Conference on Radiation Protection in NuclearScience and Technology. IIT, Kanpur, Feb. (1982) Also in Bull*of Radiat. Protection (IARP) 5 (1982) 103.

26. Thermoluminescence response characteristics of CaFa:Tm to X andgamma radiation-applications in high LET radiation dosimetry,A.R.Lakshmanan, Bhuwan Chandra and R.C. Bhatt, Ibid, IARP, Bull.5 (1982) 3.

27. A comparative study of dosimetric properties of MgaB«OT:Dysintered pellets and CaSCu :Dy Teflon discs, P.P. Szabo, A.S.Pradhan and Bhuwan Chandra, Tenth IARP Conf. on Radiation RiskAssessment, Present and Future Considerations, BARC, Bombay.March (1983). Also Bull. Rad. Prot. 6 (3&4) (1983) 77.

28. Response of CaFj:Tm ribbons for low and high LET radiations,A.S. Pradhan and R.C. Bhatt, 10th Annual Conference on RadiationRisk Assement, present and future considerations, Bombay, March(1983), IARP/10/27, 43.

: 81 :

29. A new technique for fast neutron dosimetry based onphosphorescencdbf CaSCU :Dy embedded polyethylene discs atelevated temperature, A.S. Pradhan, Bhuwan Chandra and R.C.Bhatt, Sixth Conference on Medical Physics, Srinagar, Oct.(1983) C-9, 11.

30. Dosimetric characteristics of LiF (Mg, Cu, P) TLO phosphor,Bhuwan Chandra, A.S. Pradhan, A.R. Lakshmanan and R.C. Bhatt,Tenth Annual IARP Conference on Radiation Risk Assessment- Present and Future considerations, BARC, Bombay, March 1983.Also in Bull. Rad. Prot. 6 (1983) 89.

31. Usefulness of sensitized LiF (TLD-100) at low doses and itsimpact in personnel monitoring (Abstract), Bhuwan Chandra, A.R.Lakshmanan and R.C. Bhatt, Sixth Conference on Medical Physics,Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Oct.(1983). Also in AMPX Med. Phys. Bull. 8(4) (1983) 8.

32. Low dose measuring capability of a highly sensitive LiF:Mg,Cu,P. phosphor for its applications in medical physics (Abstract)Bhuwan Chandra, Ibid 9.

33. Thermoluminescence radiation dosimetry, R.C.Bhatt and S.K. Kaul,Science Report, May (1983) 270.

34. Analytical picture of effect of temperature treatment of UV andgamma ray sensitivity of CaFj based TLD, A.S. Pradhan and R.C.Bhatt, J. Phys. D. Appl. Phys., 16 (1983) 53.

35. UV dosimetry and thermoluminescence process in LizBiOrzCuA.S. Pradhan, R.C. Bhatt and S.J. Supe, Int. J. Appl. Radiat.Isot. 134 (1983) 941.

36. Thermoluminescence of Z centres in LiF (TLD-100) at elevatedirradiation temperatures, A.R. Lakshmanan, Bhuwan Chandra andR.C. Bhatt, Phys. Stat. Sol. (a) 75 (1983) 263.

37. Response of CaSO<:Dy Teflon discs to diagnostic X-rays, A.S.Pradhan and R.C. Bhatt, AMPI Med. Phys. Bull. 7 (1983) 211.

38. Phosphorescence and photonstimulated luminescence of CaS0« :Dyembedded polythene discs at elevated temperature for fast neutrondosimetry, A.S. Pradhan, Bhuwan Chandra and R.C. Bhatt, Radiat.Prot. Dosim. 5 (1983) 159.

39. Thermoluminescence response characteristics of high temperaturepeaks in LiF at low doses using photo-transfer, A.R. Lakshmananand J.W.N. Tuyn, Nucl. Tracks 7 (1983) 109.

40. Light sensitivity of some common TLD phosphors, J.W.N. Tuyn andA.R. Lakshmanan, Radiat. Prot. Dosim. 5 (1983) 121.

41. TL glow curve shapes of CaF2 :Tm and LiF to alpha and betaradiation, A.R. Lakshmanan, Radiat. Prot. Dosim. 5 (1983) 121.

42. Thermoluminescence of some dosimetry phosphors at elevatedirradiation temperature, A.R. Lakshmaman, W. Hoffmann, J.W.N.Tuyn and C. Reffnsoe, Radiat. Prot. Dosim, 5 (1983) 251.

43. Photo-transferred thermoluroinescence in LiF for high LETradiation dosimetry, W. Hoffmann. A.R. Lakshmanan and R. Spallak,Rad. Prot. Dosi. 8 (1984) 205.

: 82 :

44. Fading of reader annealed LiF (TLD-600) for thermal neutrons andgamma rays, A.R. Lakshmanan and J.W.N.Tuyn, Radial. Prot. Dosim.8 (1984) 187.

45. Dosimetric characteristics of a new LiF TLD phosphor, S.S.Shastry, R.C. Bhatt and K.G. Vohra, Rad. Prot. Dosim. 6 (1984)335.

46. Some parameters of low and high LET radiation dosimetry usingCaF2:Tm TLD's, A.S. Pradhan and R.C. Bhatt, Radiat. Prot. Dosirtl.6(1984) 175.

47. Photo-transfer thermoluminescence in CaSO«:Dy. A.S. Pradhan andR.C. Bhatt, J. Phys. D. Appl. Phys. 17 (1984) 1699.

48. Annealing and reusability of CaFj :Tm (TLD-300) ribbons, A.S.Pradhan, K.Olthoff-Muenter and J. Rassel, Radiat. Prot. Dosim. 9(1984) 273.

49. Fast neutron thermoluminescence response of CaFz:Tm (TLD-300)-Influence of encapsulating material, A.S. Pradhan, J. Rassow, P.Meissner and K. Olthaff-Muenter, Radiat. Prot. Dosim. 9 (1984)269.

50. TL emission spectra of Dy doped TLD's, A.S. Pradhan, BhuwanChandra and R.C. Bhatt, Int.J. Appl. Radiat. and Isot. 35(1984) 226.

51. Some dosimetric parameters of MgzB<O7:Dy sintered pelletsand CaSO4:Dy Teflon discs-Acomparative study, P.P. Szabo, A.S.Pradhan and Bhuwan Chandra, Int. J. Appl. Radiat and Isot.35 (1984) 415.

52. Photon energy dependence of sensitized LiF (TLD-700) phosphor,A.R. Lakshmanan, C. Raffnsoc and J.W.N. Tuyn, Int. J. Appl.Radiat. and Isot. 35 (1984) 418.

53. Incompatibility of radiation induced oensitization andreestimation at low absorbed doses in LiF-TLD-100 (Abstract),Bhuwan Chandra, A.R. Lakshmanan and R.C. Bhatt, NationalSymposium on Thermally Stimulated Luminescence and RelatedPhenomena, PRL, Ahmedabad, Feb. (1984) 0-22.

54. TL emission spectra of rare earth doped TLDs (Abstract) A.S.Pradhan, Bhuwan Chandra and R.C. Bhatt, Ibid. P-52.

55. Phototransfer TL and thermal quenching in CaSO«:Dy (Abstract),A.S. Pradhan and R.C. Bhatt, National Symp. on thermallystimulated luminescence and related phenomena, PRL Ahmedabad,Feb. (1984) 0-41.

56. Fast neutron dosimetry with CaSCU :Mn thermoluminescent phosphorembedded Teflon discs for medical applications (abstract), S.S.Shinde and R.C. Bhatt, Xlth Annual Conference on RadiationProtection, Jodhpur (1984) SV/8, 33.

57. A thermoluminescence method for dosimetry of therapeuticallyused d(14) Be-neutron beams using sulphur activation in CaSO< :0y(TLD-900) pellets, A.S. Pradhan and J. Rassow, 15thWissenchaftliche Tagung der Gassellshft fuer Madizinsche Physikev. Nurenberg (1984) 151.

: 83 :

58. Spectral dependence of response coefficients and applicability ofthe two peak TLD method in mixed neutron photon radiation fields,J. Rassow, J.J. Broerse, R. Duer, F.W. Hensley, S. Marquebreque,K.Olthoff-Muenter, A.S. Pradhan, A. Temme, S. Vynckier and J.Zoetlief, Proc. 5th Symp. on Neutron Dosimetry, GSF NeurenbergSept. (1984) 783.

59. Modified Z centre model for thermoluminescence in LiF TLDphosphor, A.R. Lakshmanan, 7th Int. Conf. Solid State Dosimetry,Ottawa, Canada, Sept. (1983) Also Rad. Prot. Dosim. 6 (1984) 52.

60. A combination of TLD albedo and sulphur activation techniquesfor fast neutron personnel dosimetry, J.W.N. Tuyn and A.R.Lakshmanan, Ibid. Rad. Prot. Dosim. 6 (1984) 237.

61. Some parameters of low and high LET radiation dosimetry usingCic'a :T« TLDs, A.S. Pradhan and R.C. Bhatt, Ibid. Radiat. Prot.Dosim. 6 (1984) 171.

62. Thermoluminescence studies in LiF dosimeters irradiated at 77K,A.R.Lakshmanan, Bhuwan Chandra and R.C. Bhatt, First NationalSeminar on Defects in Insulating Solids, R.I.T., Jamshedpur,Nov. (1985), Abstract No. DRI-5.

63. Effect of Li doping on thermoluminescence response of CaSCU :Dyphosphor, Bhuwan Chandra, S.S. Shinde, A.R. Lakshmanan and R.C.Bhatt. Ibid (1985) Abstract No. DOP-17.

64. Measurement of fast neutron and gamma ray doses oftherapeutically used d(14)+Be-neutrons using 200°C and 270°Cglow peaks of TLD-700, A.S. Pradhan, J. Rassow and P. Meissner,Proc. Tagung Medizinsche Phyaik 1985, Bern, Switzerland, (1985)240.

65. Thermoluminescence studies in LiF dosimeters irradiated at 77Rand their implications on theoretical models, A.R. Lakshmanan,Bhuwan Chandra, R.C. Bhatt. W. Hoffmann and R. Spallek, J. Phys.D: App|.. Phys. 18. (1985) 1673.

66. Incompatibility of radiation induced sensitization andre-estimation at low absorbed doses in LiF (TLD-100), BhuwanChandra, A.R. Lakshmanan and R.C. Bhatt, Nucl. Tracks 10 (1985)77.

67. Dose dependence of photo-transfer thermoluminescence in CaSO«:Dy,A.S. Pradhan and R.C. Bhatt, J. Phys. D. Appl. Phys. 18 (1985)317

68. Phototransfer TL and thermal quenching in CaSO<:Dy, A.S. Pradhanand R.C.Bhatt, Nucl. Tracks 10 (1985) 101.

69. Additivity of fast neutron and gamma ray induced thermolumi-nescence and reusability of CaFz:Tm (TLD-300) ribbons, A.S.Pradhan, J. Rassow and K.Olthoff-Muenter, Int. J. Appl. Radiat.Isot. 36 (1985) 103.

70. Dosimetry of fast neutron beams using CaSO«:Dy (TLD-900)pellets, Nucl. Instrum. Methods in Phys. Res. 236 (1985)396.

71. In-phanton dosimetry using CaFa:Tm (TLD-300) ribbons, A.S.Pradhan, J. Rassow, K. Olthoff-Muenter, W. Baumhoer and P.Messner, Int. J. Appl. Radiat. Isot. 36 (1985) 619.

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Dosimetry of ch 4+Be neutrons with the two peak method of LiFTLD-700, A.S. Pradhan J. Rassow and P. Meissner, Phys. Med. Biol.30 (I y 3t) :. H -19 .Influence ,.f various parameters on photon energy response ofT L L ' s .and their impact on radiation dosimetry, A.S. Pradhan,Nucl. Sci. J. 22 (1985) 104.Radiation induced thermoluminescence of CaFa:Tm detector(Abstract), A.S. Pradhan and J. Rassow, 3rd Int. Symp. onAviation Fh^sics, Ferrara, Italy, Sept. (1985) 124.Comparative dosinetric studies on three low-Z phosphors, BhuwanChandra, S.S.Shxncle and R.C. Bhatt, 12th Annual Conference ofIARP Bombay.. March (1985). Also in Bull, of Radiat. Prot.8 (1985) 53.Thermoluminescence of alkali halides doped with alkaline earthimpurities, A.R. Lakshmanan and S.V. Moharil, Bull. Mat. Sci,8 (1986) 541.A study of the peak ratios in CaF2 :Tm (TLD-300) as a function ofthe beta energy, A.R. Lakshmanan, Radiat. Prot. Dosim. 12 (1986)375.Study of the TL characteristics of LiF (Mg, Cu) phosphor for itsuse in medical physics, Bhuwan Chandra, S.S. Shinde and R.C.Bhatt, Proc. Asian Regional Conf. on Medical Physics, Dec.(1986).Also in Med. Phys. Bull. AMPI 11 (1986) 569.Dosimetry of mixed fields of neutrons and gamma rays usingsensitized and unsensitized LiF TLD-700, A.S. Pradhan, R.C. Bhattand J. Rassow, Proc. Asian Regional Conference on Med. Phys.,Dec. (1986) 515.Detection of leakage neutrons from medical electronaccelerators using TLDs, A.S. Pradhan, R.C. Bhatt and S.J.Supe, Proc. Asian Regional Conf. on Med. Phys. Dec. (1986)516.General principles of radiation protection monitoring andpersonnel monitoring, A.S. Pradhan, 4th workshop onRadiation Protection, Lucknow, Oct. (1986).Film processing, developing, storage and doses to patients,A.S. Pradhan, 4th Workshop on Radiation Protection.Lucknow. Oct. (1986).Role of vacancies in the thermoluminescence of LiF:Ti andCaSO<;Dy.; Bhuwan Chandra, A.R. Lakshmanan, S.S. Shinde and R.C.Bhatt, 8th International Conf. on Solid State Dosimetry,Oxford,U.K.. August, 1986, Radiat. Prot. Dosim. 17 (1986) 451.Application of thermoluminescence dosimeters for personnelmonitoring in India, A.R. Lakshmanan, Bhuwan Chandra, A.S.Pradhan and S.J. Supe, Ibid., Radiat. Prot. Dosim. 17 (1986) 49.Fast neutron response of CaFa :Tm teflon TLD discs of differentthicknesses, A.S. Pradhan, J. Rassow and W. Hoffman, Radiat.Prot. Dosim. 15 (1986) 233.A comparative study of some CaSO« thermoluminescent phosphorsfor radiation dosimetry, A.R. Lakshmanan, S.S. Shinde and R.C.Bhatt, Radiat. Prot. Dosim. 16 (1986) 237.

: 85 :

87. Laser heating as a potential replacement for the conventionalheating of TLDs - A Comment, Bhuwan Chandra, A.R. Lakshmanan,S.S. Shinde and R.C. Bhatt, Radiat. Prot. Dosim. 18 (2) (1987)114.

88. Comments on "Large enhancement of TLD-100 sensitivity byirradiation in a reactor core", A.R. Lakshmanan, Bhuwan Chandraand R.C. Bhatt, Nucl.Instr. and Meth. B. 26 (1987) 557.

89. Annealing and re-usability characteristics of LiP-700 Chips,A.L. Lakshmanan and J.W.N. Tuyu, Radiat. Prot. Dosim. 18 (1987)229.

90. Thermoluminescence of CaFz:Tm (TLD-300) and LiF (TLD-700) fordosimetry of therapeutically used P(65) + Be Past neutrons, A.S.Pradhan, S. Vynckier and J. Rassow, 9th Conference on AMPIMed. Phy. Bull. 12 (4), paper II/3 (1987).

91. Radiation induced thermoluminescence in CaFa:Tm detectors,A.S. Pradhan and J. Rassow, Nucl.Instr. Meth. in Phys. Res.A 255, (1987) 234.t

92. Vikiran KarminkonK? Suraksha Ka Monitoran, A. S. Pradhan,Vaigyanik 4, (1986) 24.

93. Thermoluminescence of CaFa:Tm - Emission spectrum and influenceof heat treatment, A.S. Pradhan and R.C. Bhatt, Bull, ofRadiat. Prot. 10, (1 and 2) (1987) 69.

94. Role of F centres on the thermoluminescence process in pure anddoped LiF crystals, A.R. Lakshmanan, Bhuwan Chandra and R.C.Bhatt, Bull, of Radiat. Prot. 10, (1 & 2) (1987) 105.

95. A comparative study of some calcium sulphate basedthermoluminescent phosphors for radiation dosimetry, S.S.Shinde, A.R. Lakshmanan and R.C.Bhatt, Bull, of Radiat. Prot.10 (1 and 2), (1987) 169.

96. Radiation damage in LiF:Mg, Ti and CaSCU :Dy TLD phosphors,Bhuwan Chandra, A.R. Lakshmanan, S.S. Shinde and R.C. Bhatt,Bull, of Radiat. Prot. 10, (1 and 2 ) (1987) 173.

97. Effect of pre-and post-irradiation temperature treatments on theTL characteristics of various TL peaks in LiF TLD-100, BhuwanChandra, A.R. Lakshmanan and R.C. Bhatt, Seventh NationalSymposium on Radiation Physics, Mangalore University, Nov.1987 (Abstract No. 68).

98. Grain size and dysprosium concentration effects inthermoluminescent CaSO* :Dy, A.R. Lakshmanan, S.S. Shinde andR.C. Bhatt, Seventh National Symposium on Radiation Physics,Mangalore University, Nov. 1987 (Abstract No. 69).

99. Some aspects of photo-transfer thermoluminescence, A.S. Pradhan,R.C. Bhatt and S.J. Supe, Seventh National Symposium onRadiation Physics, Mangalore University, Nov. 1987(Abstract No. 70).

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Population exposure _studi

100.Competing quasi continuous trap distribution model as applied toCaSO*:Dy, J.K. Srivastava and S.J. Supe, Proc. Nucl. Phys. Solidstate physics symposium, Banaras Hindu University, Dec. (1982).

101.Thermoluminescence of CaSO<:Dy - Differential analysis ofstopping power dependent TL response characteristics, J.K.Srivastava and s. J. Supe, 9th Annual conference of IARP IndianInstitute of Technology, Kanpur, Feb. 1982, Bull, of Radiat.Prot. 5 (1982! 139.

102.Extended linearity of dose-TLi response relationship of CaSO« :Dy,J.K. Srivastava and S.J. Supe, 5th Annual conference of AMPI,Coimbatore, January, AMPI Med. Phys. Bull. (1982) C 16.

103.Genetic risk during radiotherapeutic treatment of cancer ofpenis, S.J. Supe, J.B. Satane and A.C. Malwade, Xth Annualconference of IARP, Bombay, March (1983).

104.Comparison of treatment plans for early and late stage ofCa-cervix based on iso-effect lines: S.J. Supe, J.B. Sasane,J.G.R. Solomon, and Koteshwara Rao, Vlth Annual Conference ofAMPI, Srinagar, October C1983).

105.Time dose relationship for multiple daily fractionationtreatment regimes of radiotherapy: a preliminary report, S.J.Supe, J.B. Sasane, J.G.R. Solomon, V. Balasundaram, H. Nagaraj,Vlth Annual Conference of AMPI, Srinagar, October, (1983).

106.Dosimetric approach to reduced nonlinearity of TL response ofCaSO<:Dy, J.K. Srivastava and S. J. Supe,Radiochem. Radioanal.Letters, 57 (1983) 1.

107.Trap distribution analysis of CaSO«:Dy, J.K. Srivastava and S.J. Supe, J. Phys. D, Appl. Phys. 16 (1983) 1813.

108.CRE for multiple daily fractionation treatment regimes ofradiotherapy, S.J. Supe, J.B. Sasane, J.G.R. Solomon, V.Balasundaram, Vllth Annual Conference of AMPI, Calcutta, November(1984) .

109.Implant volume size and time dose factors TDF in brachytherapy,S.J. Supe, J.B. Sasane and M.K. Gupta, Vllth Annual Conference ofAMPI, Calcutta. November (1984).

110.Determination of activation energies and frequency factors ofCaSO« :Dy TL Phosphor, J.K. Srivastava and S.J. Supe, Proc. 7thInt.Conf. Solid State Dosimetry, Ottawa, Canada, Sept.Cl983).Radiat. Prot. Dosim. 6 (1984) 41.

Ill.Mechanism of nonlinear TL response characteristics of TLPhosphors, J.K. Srivastava and S.J. Supe, Proc. 7th Int. Conf.Solid State Dosimetry, Ottawa, Canada, Sept.(1983)Radiat.Prot. Dosim. 6 (1984) 45.

112.Reusability of thermoluminescence of CaSO«:Dy, J.K. Srivastavaand S.J. Supe, XI Annual Conference of IARP Defence Laboratory,Jodhpur, Feb. (1984). Bull, of Radiat. Prot. 7(1984), 77.

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113.Detrappig processes during cooling courses of thermal bleachingcycle and initial rise method, J.K. Srivastava and S.J. Supe,National Symposium on Theory and Practice of Thermally StimulatedLuminescence and Allied Phenomenon, Physical Research Laboratory,Ahmedabad, Feb.(1984).

114.TL of common TLD phosphors and competing TL trap distributionmodel, J.K. Srivastava and S.J. Supe, National Symposium onTheory and Practice of Thermally Stimulated Luminescence andAllied Phenomenon, Physical Research Laboratory, Ahmedabad, Feb.C1984).

115.Effect of radiation quality on TL fading, J.K. Srivastava andS.J. Supe, Vlluh Medical Physics Con£., Calcutta, November (1984).AMPI Med. Phys. Bull. 9 (1984) 36.

116.A case of improper handling of brachytherapy sources, J.K.Srivastava and S.J. Supe, VII Medical Physics Conference,Calcutta, Nov. (1984). AMPI Med. Phys. Bull. 9 (1984) 36.

117.Thermoluminescence of CaSO«:Dy and yadiation damage, J.K.Srivastava and S.J. Supe, Proc. Symp. Radiation Effects in Solids,BARC, Bombay, Nov. (1985) 485.

118.Thermoluminescence of CaSO*;Dy - A semtempirical approach forqualitative analysis of nonlinear TL effects, J.K. Srivastavaand S.J. Supe, Phys.Stat. Sol. (a), 92 (1985) 573.

119.Relative effect of alpha and gamma radiations on thermallystimulated luminescences of CaSO<:Dy, J.K. Srivastava and S.J.Supe, National Seminar on Defects in Ionising JJolids, RegionalInstitute of Technology Jamshedpur, Nov. (1985) DRI-4.

120.Effect of radiation quality on TL fading of CaSCU :Dy in highdose region, J.K. Srivastava and S.J. Supe, Nucl. Instr. Meth. inPhys. Res. A 243 (1986) 567.

121.Effect of higher temperature treatments on reusability ofCaSO< :Dy TL phosphor exposed to increfsingly high gamma doses,J.K. Srivastava and S.J. Supe, J. Raiioanal. Nucl. Chem. Letters104. (1986) 245.

122.On mechanism of radiation damage of thermoluminescence ofCaSO«:Dy, J.K. Srivastava and S.J. Supe, National Seminar onSolid State Physics, The Golden Jubilee Celebrations of IndianPhysical Society, Jadavpur, Calcutta, Feb. 1985, Indian J.Phys. 60A (1986) 170.

123.Dependence on LET of TL responsu characteristics of CaSO<:Dy,J.K. Srivastava and S.J. Supe, Reactor Research Centre,Kalpakkam March (1986).

124.Gamma radiation and thermal treatments for improving glow curvestructure of CaSO«:Dy, J.K. Srivastava and S.J. Supe, Proc.AsianRegional Conference on Medical Physics, Bombay, Dec. (1986) 573.

125.Determination of radiation exposure to patients and personnelduring percutaneous nephrolimtomy-a new fnterventionalradiological technique of removing Yenal calculi: S.J. Supe,J.B. Sasane and D.M. Kooka, K.Khandelwal and S.S.Dagaonkar, AMPI Bull., 11 {1986) 481.

j 88 i

126.TSD for multiple daily fractionation treatment regimes ofradiotherapy , S.J. Supe, J.B. Sasane, J.G.R. Solomon, AsianRegional Conference On Medical Physics of AMPI 1986, AMPI Bull,11,(1986) 331.

127.Volume correction factor in time dose relationships inbrachytherapy^ S.J. Supe, J.B. Sasane and M.K.Gupta,Strahlentherapie 163 (1987) 309.

Personnel monitoring service

128.Reliability of a TLD system for routine personnel monitoring,M.M. Adtani, A.V. Dere, R.V. Dhond, P.H. Patel and S.J. Supe,Radiat. Prot. Dos. 2, (1982) 43.

129.Comparison of doses evaluated using personnel monitoring films andTLD badges for X and gamma radiations (Abstract), A.V. Dere, A.S.Patil, K.L. Popli, B.D. Phadke, K.S. Shenoy, Vth Ann. ConferenceAMPI, Coimbatore, (1982).

130.Evaluation of personnel doses using TLD badge in mixed field of X,gamma and beta radiations, (Abstract), R.K. Kher, A.V. Dere, K.L.Popli. M.P. Sankaran, R.M. Worlikar and S.J. Supe, Vth Ann.Conference, AMPI, Coimbatore, (1982).

131.Comparison study of personnel monitoring systems in India,(Abstract), M.M. Adtani, A.V. Dera, R.V.Dhond, P.H. Patel and S.J.Supe, Vth Ann. Conference, AMPI, Coimbatore (1982).

132.Occupational exposures to medical personnel, K.S. Shenoy, R.V.Dhond, P.H. Patel, and S.J. Supe, Vth Ann. Conference, AMPI,Coimbatore, Jan. (1982). (Abstract).

133.Methods of assessment of individual and collective doses totransport workers and members of public during transport- ofradioactive materials, K.G. Vohra, G. Subrahmanian, R.K. Kher,A.N. Nandakumar and S.R.K. Iyer, IAEA Report on Research ContractNo. RC/2740 (Oct. 1983).

134.Experiences in the use of TLD badge for personnel monitoring, R.K.Kher, M.M. Adtani, S.J. Supe and K.G. Vohra, Bull, of Radiat.Protec. 6 (1983) 83.

135.Application of hybrid-lognormal distribution for analysis ofoccupational dose distributions, R.K. Kher, K.S. Shenoy and S.J.Supe, Bull, of Radiat. Prot. 6 (1983) 109.

136.Significance of parameter in comparison of personnel dose data ofoccupational workers, (Abstract), R.K. Kher, J.S. Bisht, K.S.Shenoy and Patel P.H., Xth IARP Conf. on Radiation Protection,BARC, Trombay (1983).

137.Cancer risk estimation for industrial radiography personnel, K.S.Shenoy, R.K. Kher, P.H.Pardasani, R.V. Dhond, P.H. Patel andS.J. Supe, Bull, of Radiat. Prot. 6 (1983) 65.

138.A study of application of effective dose equivalent (EDE)concept in the case of medical radiation workers, A.S. Patil,Sankaran M.P.,R.K. Kher and P.H. Patel, Bull, of Radiat. Prot,8 (1983) 151.

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139.Assessment of radiation dose received by workers during thetransport of radioactive material - Development of a model, K.G.Vohra, G. Subrahmanian A.N. Nandakumar, R.K. Kher and S.R.K.Iyer, Radiat. Prot. Dos.9 (1984) 283.

140.A method of assessment of annual collective do3e received by urbanpublic due to transport of radioactive material, K.G. Vohra,G.Subrahmanian, A.M. Nandakumar, R.K. Kher and S.R.K. Iyer,Radiat. Prot, Dos. 9, (1984), 287.

141.Dose estimates using DRP criticality bad^e in IAEA Internationalintercomparison study on NAD-1983, (Abstract), R.K. Kher, N.P.S.Sidhu, and S.J. Supe, Xlth IARP Conf. on RadiationProtection, Defence Lab., Jodhpur, Feb. (1984).

142.The use of TLD badge for medical radiation workers - a comparativestudy with film badge, R.K. Kher, A.V. Dere, V.H. Pendurkar,P.H. Patel and S.J. Supe, Bull of Radiat. Prot. 8 (1985) 21.

143.Contribution of electron dose from sealed gamma sources in thecalibration for personnel monitoring systems, K.L. Popli,V.H. Pendurkar, A.V. Dere, S.M. Rao, R.K. Kher, Bull, of Radiat.Prot* 8 (1985) 25.

144.Conversion factors for evaluation of effective dose equivalent forreactor personnel, M.M. Adtani, Bhoja Shetty and S.J. Supe,Radiat. Prot. Dos., (1985).

145.Use of thermoluminescent dosemeters for personnel monitoring (PartII) Evaluation of ICRP person dose and risk estimation forreactor personnel, M.M. Adtani, Ph.D. Thesis, University ofBombay, (1986).

146.Assessment of axial gamma dose rate profile on irradiated fuelassembly using polycarbonate film and perspex dosemeters, V.S.Joshi, S. Janakiraman, P.R. Pillaim, K. Somanathan, K.K.Narayanan, John Jacob, K.L. Kutty, K.L. Popli and V.R. Deo,.Bull, of Radiat. Prot, 9 (1986) 59.

147.Retrieval and recycling studies of used TLD discs for personnelmonitoring, K.L. Popli, R.K. Kher, S.S. Sanaye, K.S. Shenoy andS.J. Supe, Bull, of Radiat. Prot. , 9 (1986) 23.

148.Effects of backscatter photons and build up electrons in thedesign of TLD badge, A.V. Dere, A.S. Patil, B. Shetty, K.L. Popliand R.K.Kher, Bull, of Radiat. Prot. , 9 (1986) 19.

149.Monte Carlo calculations of dose distributions in the ICRUspherical phantom^ S.K. Gupta, R.K. Kher and S.J. Supe, Med.Phys. Bull. 11 (1986) 561.

150.Depth dose measurement using TL dosemeters for Co-60 andmegavoltage photon beams, V.K. Nelson, K.L. Popli and R.K. Kher,Med. Phys. Bull., 11 (1986) 147.

151.Measurement of dose equivalent index quantities in the ICRU sphereusing TLD discs, K.S. Shenoy, K.L. Popli, S.K. Gupta, D. Krishnan,R.K. Kher and S.J. Supe, Med. Phys. Bull, 11 (1986) 531.

152.Recycling studies of the treated TLD dosemeters, S.S. Sanaye, K.L.Popli, B.D. Phadke, R.K. Kher, P.H. Patel and S.J. Supe, Bull.Radiat. Prot., 10 (1987) 113.

s 90 :

153.Dose analysis in an industrial radiography institution, K.S.Shenoy, R.K. Rher and S.J. Supe, Bull. Radiat. Prot ., 10(1987) 157.

154.Methods of assessment of individual and collective doses totransport workers and members of public during the transport ofradioactive material, K.G. Vohra, G. Subrahmanian, A.N.Nandakumar, R.K. Kher and S.R.K. Iyer, IAEA-TECDOC 375 (1986)35.

155. Ext.ei nai hrambtrahlunc? contribution to the absorbed dose inCdSO< :Dy discs used for personnel monitoring by completeabsorption of beta rays in the photon energy compensating filters/s.K.Ct.,pta, R.K. Kher and S.J. Supe, Bull, of Radiat. Prot ., 9(1 9 S t. > 4 9 .

156. Precision and accuracy of TL. personnel monitoring dosemeters, P.Ayyapan and M. Sethuraman, Med. Phya. Bull. 11 (1986) 532.

157.Studies on personnel monitoring Cor external radiation, R.K. Khar.Ph.D. Thesis, University of Bombay, (1986).

158. Radiosensitisation by m«s«inidazQle, studies* on production andrepairs of single strand breaks in Yoshida ascites tumor cells,D.R. Singh, C.K.R. Nair and D.S. Pradhan, Proc. of the Symp. onmodifiers of radiosensitivity in radiotherapy, Madras, Dec.(1982) .

159.Radiotherapeutic trials with hypoxic sensitizers, (Abstract),D.R. Singh, D. Krishnan and U. Madhvanath, Proc. IVth Congress ofAsso. of Radiation Oncologists of India, Madras, Dec. (1982).

160.DNA repair in Yoshida ascites tumor cells exposed to gammaradiation with mesenidazfile, (Abstract), D.R. Singh, C.K.K. Nairand D.S. Pradhan, Symp. on DNA Repair and Chromosome Aberations,Varanasi, Dec. (1983).

161.Electron transport in one-diroensional finite system, S.K. Gupta,Ind.Xof Phys. 58A, (1984) 442.

1S2.Elastic scattering cross-section of electrons in detectormaterials, S.K. Gupta and Ram N v Indian Journal of Physics,58A (4 ex. 5) (1984) .

163.Computerised shielding calculations of a Co-60 teletherapyinstallation., (Abstract), S.K. Gupta, M. Ahmed and G.Subrahmanian, Annual Conf. of IARP, Jodhpur, Feb. (1984).

164.A different approach for the application of Monte Carlo method toelectron transport, S.K. Gupta and M.A. Prasad, Nucl. Sci. Sngg.,90 (1985) 256.

165..State of medical brachytherapy departments in India - someobservations, H.K. Kundu, R.L. Pandey and G. Venkataraman, Bull.Radiat. Prot., 6 (1983) 55.

166.Occupational exposure trend in inustrial rndiogrphy, (Abstract),P.H. Pardasani, R.V. Dhond, P.H. Patel And S.J. Supe, IXth AnnualConf. of IARP, Kanpur, Feb. (1982).

167.Dosimetric characteristics of a new type of personnel monitoringfilm, (Abstract), R.V. Dhond, P.H. Patel, K.S. Shenoy, P.V. Sathe,and S.J. Supe, Vth Annual Conf. of AMP I, Cointbatore, Jan. (1982).

: 91 *

168.Occupational exposure to dial painters using radiolouminescentcompounds, (Abstract), K.S. Shenoy, P.H. Pardasani, R.V. Dhond,P.H. Patel and S.J. Supe, International Conf. on Applications ofRadioisotopes and Radiation in Industrial Development (ICARID),Bombay, March (1984).

169.Analysis of excessive exposures to industrial radiographypersonnel in India (1978-82), (Abstract), R.V. Dhond, R.L.Pandey, K.S. Shenoy, P.H. Patel and S.J. Supe, InternationalConf. on Applications of Radioisotopes and Radiation in IndustrialDevelopment (ICARID), Bombay, March (1984).

170.Incidences of excessive exposures to industrial, medical andresearch radiation workers in India (1978-1983) and theirinvestigations, R.V. Dhond, R.L. Pandey, K.S. Shenoy, P.H. Pateland S.J. Supe. Xllth Annual Conf. of IARP, Bombay, March (1985).

171.Analysis of excessive exposures received by radiation workers inmedicine, industry and research organisations, R.L. Pandey, P.H.Patel and S.J. Supe. Bull, of Radiat. Prot. 9 (1986) 99.

172.Dose density response and latent image fading in Kodak type2 personnel vnonitoring films in a water proof plastic packing,M.Thomas, R.L. Pandey, P.H. Patel and S.J. Supe, Bull, of Radiat.Prot. (1986) 53.

173.Risk assessment of medical radiation workers, R. Sadagopan, P.H.Pardasani, S.J. Supe and P.H. Patel, Med. Phys. Bull. 11 (1986)563.

174.Recycling studies of the treated TLD discs, S.S. Sanaye, K.L.Popli, B.D. Phadke, R.K. Kher, P.H. Patel and S.J. Supe, Bull.of Radiat. Prot. 10 (1987) 113.

175.Dose analysis in an industrial radiography institution, K.S.Shenoy, R.K. Kher and S.J. Supe, Bull, of Radiat. Prot. 10 (1987)157.

176.Measurement of scatter radiation and secondary electrons in theuse of calibration sources, K.L. Popli, A.V. Dere, R.K. Kher andS.J. Supe, Seventh National Symposium on Radiation Physics(NSRP-7) Mangalore, (1987), Abstract No.12.

177.Bremsstrahlung energy spectrum and exposure rate in air fromelectrons (4-20 Mev) incident on thick tantalum target, S.K. Guptaand S.J. Supe, Seventh National Symposium on Radiation Physics(NSRP-7) Mangalore, (1987), Abstract No. 39.

178.Influence of tritium on CaSO4:Dy TL personnel monitoringsystem, P. Ayyappan, K.R. Vishwambaran and M. Sethuraman, Bull.of Radiat. Prot. 10 (1987) 17.

179.Intercomparison of thermoluminescence and direct readingdosimeters, M.G. Kadwani and R.M. Sharma, Bull, of Radiat. Prot.10 (1987) 5.

180.Estimates of uncertainty in the collective dose due to zero dosereports, R.K. Kher, K.S. Shenoy, H.K. Kundu, K.L. Popli and S.J.Supe, IXth Conferenceon Medical Physics,Trivandrum (1987). AMPIMed. Phys. Bull. 12(4), 31 (1987), Paper V /24.

181.Cancer risk estimation among radiation workers in medicine inIndia, K.S. Shenoy and R.K. Kher, IXth Conference on MedicalPhysics, Trivandrum, (1987), AMPI Med. Phys. Bull. 12(4), 32(1987), Paper V /25.

182.Study of defects in CaSO*:Dy embedded systems, M.M.Adtani, Bhuwan Chandra and S.J. Supe, XI h Conference on MedicalPhysics, Trivandrum, (1987). AMPI Med. Phys. Bull. 12(4),36(1987), Paper V/31.

183.Measurement of radiation levels around radiotherapy facilitiesusing thermoluminescent dosimeters, K.L. Popli, K. Unnikrishnan,H A . Sabuwala and S.J. Supe, IXth Conference on Medical Physics,Trivandrum, (1987), AMPI Med. Phys. Bull. 12(4),38 (1987),Paper V /38.

184.A suggested modificaion in a commercially available personnelmonitoring film pack to improve its suitability in high humidityareas, R.V. Dhond, R.M. Worlikar, M.P. Shankaran and P.K. Patel,IXth Conference on Medical Physics, Trivandrum, (1987), AMPI Med.Phys.Bull. 12(4), 29 (1987), Paper V/23.

Neutron monitoring group

185.Computed response of Kodak NTA dosimeter to moderated neutronspectra, O.P. Massand and D. Singh, Health Phys. 42 (1982) 226.

186,Further studies on latent image fading in Kodak NTA fast neutronpersonnel monitoring films, O.P. Massand, H.K. Kundu and P.K.Marathe, Bull, of Rad. Prot. 5 (1982) 67.

187.Computed response of rem counter for moderated neutron spectra,O.P.Massand, M.P. Dhairyawan and 0. Singh, Bull, of Rad. Prot.5 (1982) 71.

188.Radiological safety in the use of radioactive neutron sources inindustrial & research establishments, O.P. Massand, Safety GuideRPG/IND-2, BARC, 1982.

189.Effective dose equivalent for some of the neutron sources inindustry and research, M.P. Dhairyawan, Bull, of Rad. Prot. 6(1983) 29.

190.Effective dose equivalent and derived fluence limits for leakageneutron spectra, M.P. Dhairyawan, Tenth IARP Conference, Bombay(1983) .

191.Neutron measurements in 10 MV Siemens Mevatron-12 electronaccelerator, S.P. Agarwal, A. Sharma, D. Singh, P.K. Marathe andG. Subrahmanian, Tenth IARP Conference, Bombay (1983).

192.Effective dose equivalent for leakage neutron spectra, M.P.Dhairyawan and G. Venkataraman, Rad. Prot. Dos. 4 (1983) 105.

193.Women and ionising radiation, M.P. Dhairyawan and G. Venkataraman,Radiology Congress, Bangalore, (1984).

194.Radiological safety in the use of well logging devicesincorporating radioactive neutron and gamma ray sources, O.P.Massand, Safety Guide RPG/IND-5, (1984).

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195.Design of albedo neutron dosemeters using *LiF TL detectors,(Synopsis) M.P. Dhairyawan, G. Venkataraman and O.P. Massand,Eleventh IARP Conference, Jodhpur (1984).

196.Calculations of response to representative neutron spectra ofalbedo neutron dosemeters incorporating LiP detectors, G.Venkataraman, M.P. Dhairyawan and O.P. Massand, Rad. Prot. Dos. 3(1984) 25.

197.Radiation risk and uomen, M.P. Dhuiryawan, Seventh InternationalConference of Women Engineers and Scientists, Washington D.C.,(1984) 25.

198.Radiological safety in radioactive well logging, O.P. Massand,Bull. Rad. Prot. 7 (1984) 41.

199.Case study of radiation incident involving, a 60Co radiographiccamera, P.K. Marathe, N. Sankarnarayanan and V.G.R. Subramanian,Bull. Rad. Prot. 7 (1984) 69.

200.Some neutron measurements at 15 MV Varian Clinac - 20, O.P.Massand and U.B. Tripathi, Bull. Rad. Prot. 8 (1985) 73.

201.Comparison of fast neutron RBE values based on old and revisedatom bomb dosimetry, P.K. Marathe, Gouri Unnikrishnan and D.Krishnan, Bull. Rad. Prot. 8 (1985) 21.

202.Fast neutron personnel monitoring, O.P. Massand, H.K. Kundu, M.P.Dhairyawan, P.K. Marathe, Report BARC/DRP/FNM 1, 1985.

203.Computed response of CR-39 solid state nuclear track detector tomoderated neutron spectra, O.P. Massand and M.P. Dhairyawan,Bull. Rad. Prot. 8 (1985) 7.

204.Implications of the recent ICRP recommendations on neutronmonitoring, M.P. Dhairyawan, G. Venkataraman and O.P. Massand,Bull. Rad. Prot. 9 (1986) 93.

Dose records and statistics group

205.Occupation exposure trend in industrial radiography, K.S. Shenoy,P.H. Pardasani, P.H. Patel, S.J. Supe, IX Annual Conference ofIARP held at Kanpur, Feb.(1982>.

206.Cancer risk estimation for industrial radiography personnel, K.S.Shenoy P.H. Pardasani, P.H. Patel, S.J. Supe, X Annual Conferenceof IARP held at Bombay, March (1983),

207.Occupational exposure trends and estimation of radiation risk indiagnostic radiology, K.S. Shenoy, P.H. Pardasani, P.H. Patel,S.J. Supe, VI Annual Conference of AMPI at Srinagar, Oct. (1983).

208.Evaluation of dose equivalent for personnel working in teletherapydepartment, S.J. Supe, P.H. Pardasani, XI Annual Conference ofIARP, Jodhpur, Feb. (1984).

209.Occupational exposure to dial painters using radioluminouscompounds, K.S. Shenoy, P.H. Pardasani, P.H. Patel, S.J. Supe,International Conference^ Applications of Radiation andRadioisotopes in Industrial Development, Bombay, March (19841).

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220.Occupational exposures in industry: Need for special supervisionon working condition-A., R. Sadagopan, S.J. Supe, P.H. Patel,International Conference^Applications of Radiation and Radio-isotopes in Industrial Development, Bombay, March £-984}.

211.Risk assessment of medical radiation workers, R. Sadagopan, P.H.Pardasani, S.J. Supe and P.H. Patel, Asian Regional Conference onMedical Physics, Bombay, Dec. Q.9B6).

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D• RADIATION PROTECTION INSTRUMENTATION SECTION

T.V. Venkateswaran

This Section has been involved in the development of severaltypes of instruments required by this Division to fulfil thedifferent functions and activities. The instruments developedcan be broadly categorized as (1) Radiation ProtectionInstruments (2) Dosimetric Instruments, (3) Personnel MonitoringInstruments and (4) Miscellaneous Instruments for research,education and training programmes.

Different type of monitors have been developed to facilitate-radiological protection surveys of medical and industrialinstallations, routine as well as those required for emergencies.These include ionisation chamber type, G.M. based andscintillation type monitors. A few instruments are controlled bymicroprocessor to compute the various parameters from theinstrument readings. An audio visual radiation alarm unit forthe safety of radiation workers is also available. For themonitoring of neutron sources and for the physical verificationof Pu-Be neutron sources supplied by BARC to variousinstitutions, neutron monitors are also developed.

The dosimeters developed in the Section are used by medicalinstitutions throughout the country for accurate dose delivery incancer therapy. For health and medical physics applicationsthermoluminescent dosimeter readers are also made. Instrumentsfor industrial application and for the application ofradioisotopes for dosimetry are also developed for demonstrationto trainees of various training programmes, organised by theDivision.

The personnel monitoring instruments required for conductingcountrywide personnel monitoring service are fabricated andsupplied by this Section.

TLD badge readers and optical densitometers have beenfabricated as per requirement and also maintained regularly.

A semiautomatic TLD badge reader incorporating a microproce-ssor has been developed.

Most of these instruments developed are import substitutesand use indigenous components wherever possible. After meetingthe requirements of the Division, some of these dosimetricinstruments are supplied to medical institutions in the country.Feedback obtained from the field use of these instruments hasbeen utilized to improve the quality of instruments fabricated.

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The technical know how developed by this Section isconstantly being transferred to commercial channels in order tomeet the growing demand of monitoring and other type ofdosimetric instruments by several institutions.

1. Radiation Protection Instruments

1 .1 Anj.lLogue__containin.ati.pn_ monitor (Ana con).

K.P. Karanth and P. Gangadharan

In this unit the contamination levels due to radioactivematerials emitting beta and gamma radiations are measured anddisplayed on a linear 0-50 micro-ampere panelmeter. The unit hasthree linear ranges 0-0.2mR/hr, 0-2mR/hr and 0-20mR/hr. Presenceof contamination levels in excess of 20 mR/hr is indicated by theglow of a miniature red LED. The unit uses an end -windowhalogen quenched G.M. tube as the radiation detector. The entireelectronic circuit has been designed using CMOS IC's and the unitworks on 4 X 1.5 volt pencil type battery cells (Eveready type1015 or its equivalent). The block diagram of the unit is givenbelow in Fig.l.

AUDIO

G.M. COUNTER

LND 7 2 3 U

c j PULSE"*j SHAPEH

OVER

RANGE

COUNTRATEMETEH

MCTER

BATTERVCELLSi * 1 5 V

F i ^ • i BLOCK DIAGRAM OF ANACON

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1.2 Digital contamination monitor (DIGICON)

K.P. Karanth, and P. Gangadharan

This portable contamination monitor has been designed formeasuring low levels of contamination from radioactive materialsemitting beta and gamma radiations. A sensitive large volume,halogen quenched G.M. Counter is used as the radiation detector.

The electronic circuit consists of a pulse shaper, fourstage decade sealer, a timer, an audio circuit for oral indica-tion and an electronically regulated EHT of 500 volts for G.M.Operation. The output of the sealer is displayed on a 4 stageLED display System. The unit works on 4 x 1.5 volt pencil typebattery cells and the minimum measurable radiation exposure is0,01 mR/hr. A circuit to indicate contamination levels more than50 mR/hr by blanking the main display has also been incorporatedin this unit. The block diagram of the DIGICON is given in Fig. 2

G.M. COUNTER

LND 723K

c

BATTERYCELLS4x1-5 V

DIGIT LED DISPIAV|

PULSESHAPER

4 STAGE DECADESCALER + DECOOER•»• MULTIPLEXER

AUDIO L.5 TIMER

BLOCK DIAGRAM OF DIGITAL CONTAMINATION MONITOR

1.3 Radiation monitor (RADMON)

V.H. Degwekar, and R.G. Khadake

A hand-held-type area monitor which can be used to monitorthe radiation field in the vicinity of industrial radiographyinstallations, telecobalt units, other sealed sources and sourcecontainers etc. has been developed. The instrument makes use of aminiature halogen quenched G.M. counter as a gamma ray detector,which has small dead time and low operating voltage. The outputof the count rate meter or the integrator is displayed on a 50 uApanel meter which is csilibrated in terms of exposure rate and

; 90 .',

exposure. ;ne monitor can iiieasutb th;1 exposure rates from 0 to20 R/hr in five different ranges ana an exposure of 100 mK fullscale on a single range. The response has been made energy inde-pendent in the energy range 80 keV to 1..13 MeV {within ± 1 5 % ) .The monitor works on 4 x 1 . 5 V torch ?. i^ht cells. The blockd I :...z ' '->'' • • i "•'"-•• v crtf.or. t s g i v e n i n F i g . J

' O S J R t R A Y C

G *•. COUNTER

16 5 5 0

r o . - » - — J muUTIVIBRATOR

EXPOSURE c '

UNIVIBRATOR

—i INTEGRAfOR r

100mR

RATE

_J 50|iA Q

REGULATED POWER

SUPPLY

AUDIOciRcurr

BLOCK DIAGRAM OF G. M BASED AREA MONITOR

1.4 Iciiis_at ion type radiation survey meter (RASHION)

A. Seethapathy and S.S. Tambe

The solid statu electrometer ionisation type radiationsurveymeter finds extensive use in monitoring radiation levelsaround radiographic installations and in measuring leakage radia-tions levels around source housing. The circuit diagram isgivenin Fig.4. The ionisation chamber has an air volume of 400cc.

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The electrometer circuit consists of a dual MOSFET (type MEM 955)followed by a micropower opamp. (type 24250). The ranging isdone by changing the feed back factor. All the front endcomponents are wired on a teflon board so as to keep the leakagecurrent contribution to the minimum. The necessary voltagesrequired are generated by a d.c. -d.c. converter. This instru-ment is capable of measuring both exposure and exposure rate inthe range of 40 mR to 40R and 40 mR/hr to 40R/hr (full scale)respectively. This light weight and rugged instrument operateson four 1.5 V pencil type batteries.

!1U»IM|I4 I

Fl4-> CinCUIt UIAGKAM OF RASMION

1.5 Industrial radiation monitors (INDRAM)

V.H. Risbud, K.C. Bajaj, M.M. Bhatt and R.R. Bhingare

These instruments are used to check the radiographic sourcehousings for shielding adequacy and other radiation monitoringpurposes. These instruments have been designed to measure theexposure rates at 5 cms from the surface of radiographic sourcehousings since the detectors are located at 5 cms from the tip ofthe conical projection. In these monitors miniature type halogenquenched G.M. counter is used. The non-linear respose of G.M.Counter is made linear with the help of a dead time correctioncircuit which helps to resolve the radiation levels at higherexposure rates. Variety of industrial radiation monitoringinstruments have been made using LED displays,LCD displays andAutoranging Analog displays. In digital display type instru-ments, shaped pulses are fed to digital displays in conjunction

JIOO:

with IC having counter, decoder and driver and in Analog typedisplays, shaped pulses are fed to a Auto-ranging countrate metercircuit. CMOS circuits are used in these monitors to minimisethe current drain and the monitors work on 4 x 1.5V pen torchcells. The box for these monitors has been made rugged, lightand easily portable. The block diagrams on Indram are given inFigS. 5 and 6.

1.6 An audio-visual radiation alarm unit for the safety ofradiation workers JRAJDWAR_Nji_

V.H. Risbud and K.C. Bajaj

This Radiation Alarm Unit is useful for the saftty of radia-tion workers in different industries, specially during certainoperations such as open field radiography. Open field radio-graphy is undertaken mainly during night time as a safety measureof non-radiation workers and population st large. In order toprevent the entry of any unauthorised person during open fieldradiogrphy, an area upto which the dose level is more than thesafe level of 0.25 mR/hr is cordoned off. The radiation workersengaged in open field radiography cannot keep a vigil on thecordoned off area, being busy with their own jobs at hand andowing to the poor visibility conditions prevailing during nighttime, an efficient portable and battery-operated audio-visualalarm giving a loud beep and an intense flash is required toalert the people who might otherwise trespass the cordoned-offarea, thereby receiving unwanted exposures.

In this unit Philips 18550 G.M. counter has been used as aradiation detector. This counter has a fairly linear responsewithout dead time correction upto lR/hr. The p-ilses from theG.M. Counter after shaping by a univibrator are fed to a countrate meter circuit, the output of which is compared against apreset voltage level by a comparator. The comparator outputstarts to charge a bank of capacitors in the charging circuit andthe rapid discharge of the capacitors through a lamp producesintense flash light and the discharge through a loud speakerproduces loud beep. The instrument works on 6 x 1.5V cells ofthe type Eveready 1050. The instrument has been made portableand rugged for field use.

1. 7 A Microprocessor controlled radiatipn survisy mejt er

S. Kannan, M.D. Lalsare and P. Gangadharan

A low power microprocessor based Portable Radiation Surveymeter has been developed for measurement of leakage radiationlevels around radioactive source housings such as radiographycamera which are routinely checked for shiulding adequacy for

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-550 V

G. M. COUNTER10 550

PULSE

SKAPER

E.H.T.

•MO

PULSE SHAPERFOR

DEAD TIMECORRECTION

BLANKING

CIRCUIT

ICM -7224

TIMER

3 Sec.

.75 Sec

BUZZER

LCD

DISPLAY

FIG. F BLOCK DIAGRAM OF INDRAM - DIG (H)

- 5 0 0 V

G.M. COUNTER18503

PULSE SHAPER

CRM CIRCUITWrTH DEADTIME CORRECT-ION

CRM CIRCUIT

PULSE SHAPERFOR DEAD TIMECORRECTION

GAIN CONTROL

RANGE

SELECTION

E.H.T.

METER

LED INDICATIONFOR DIFFERENTRANGES

FIG. 6 BLOCK DIAGRAM OF INDRAM-AUTO

: 102 :

radiation protection purposes. Often, as many as twenty readingsor more are required for assessing the maximum and averageleakage radiation levels. The microprocessor based G.M. counterRadiation Survey Meter can store upto twenty readings, computeand indicate the average, maximum and minimum levels, encoun-tered. The compact survey meter is based on the CMOSmicroprocessor Motorola MC 146805 E2 chosen for its low cost,very low power consumption and wide range of operating voltages.The block diagram of the survey meter is shown in the Fig. 7. Itconsists of a regulated EHT(-450v)for the G.M. counter (ZP 1200),a pulse shaper/preamplifier, a CMOS clock for setting thesampling time and the CMOS microprocessor system. The instrumentoperation is controlled by five push-button keys on the panel anda 4 1/2 digit LCD display provides digital readout of theexposure rate. The measurement alogrithm used is shown in theflow chart, Fig.8. The survey meter also incorporates featureslike software based dead time correction for G.M. counterresponse and energy correction for five commonly usedradioisotopes. The survey meter has a measurement range of 0.1mR/hr to 1 R/hr and it works on four pen light cells (6V).

r0 . .1

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3

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woe NO, n m

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f

FIG g MEASURE : FLOW CMAflT

1. 8 Scintillation gamma monitor

V.H. Risbud and S.B. Joshi

This instrument is a portable battery operated scintillationmonitor to detect very low exposure-rates of gamma background

: 103 :

radiation. A Nal(Tl) scintillator is used in conjunction with aP.M. Tube in this instrument. The output pulses from the P.M.Tube are shaped using a univibrator. The shaped pulses from theunivibrator are counted with a counter/decoder/driver circuit anddisplayed on a 4 1/2 digit LED display in terms of uR/hr. Atimer circuit and a sealer are used to display the counts in tworange from natural background to 1000 uR/hr and 10 mR/hr with aresolution of 0.1 uR/hr in the lower range. A regulated powersupply provides +5V for the overall operation of the circuitwhile a d.c.-d.c. converter supplies -1200 V for the P.M. tu*>e'The instrument works on four 1.5 cells of the type Eveready 1035.This instrument is being used by Pollution Monitoring Section ofDRP regularly.

1•9 X-ray monitor for diagnostic radiography (XMON)

V.H. Risbud and G. Ramanathan

A scintillation monitor with fast response time better than0.02 sec has been developed for routine monitoring around diag-nostic X-ray installations. The block diagram of the instrumentis shown in Fig. 9.

N i l(Tl )

PM TUBEEMT 9734 a

BERYLLIUMWINDOW

ATTENUATOItl f G-MN 1FOH LjAMPLiFlfH L_

f-NEHCV/ [ FOH ICCRHECTIOH| [ HANGING

PEAKVOLT-

METER

50 (MMETER

FIG <\ BLOCK DIAGRAM OF SCINTILLATION MONITOH

The instrument consists of a NaKTl) scintillator 1" x 1/2"with beryllium window coupled to EMI 9734 P.M. tube. The outputof the P.M. tube is fed to a current to voltage converter usingFET-input op.amp. RCA 3130 and the voltage developed aftersuitable correction for non air-equivalence is fed to a peakvoltmeter using IC LM 324 and FET switch CD 406i,. The output ofthe peak voltmeter is displayed on an analog meter calibrated toread exposure rates from 0-10 mR/tir to 0-10 R/hr in four dif-ferent ranges. The correction factors for air-equivalence cor-responding to different operating potentials in diagnosticradiology from 50 kV to 150 kV and suitable filtrations arederived from experimentally determined u« •>/p values and is shownin Fig. 10.

: 104 t

a:w

io

6u

z

ik1 1 >

0.8

0-6

0-4

0-2

~O—O-<1-ij-) For Water

-O—Q-(1-5^n) For Airexperimental Values

E

_L20 40 60 80 WO 120 MO

PHOTON ENERGY IN KcV

Ml ~

FIG. ID VARIATION OF ( 1 - e^-) FOR WATER AND

( i - i 1 ^ . 0 ) FOR AIR WITH ENERGY ( Based on

values from reference ) .

looor

NOTE- The experimental values shown are for a totalfiltration of 2mm At.

FIG 1 1 TIME OF EXPOSURE-RATE Vs RESPONSE

100

a.B

UJ

a.oa.

10

.01

• - RASMION RESPONSE FOR 240 mR / b

O - GUN MONITOR (ECIL MAKE )RESPONSE FOR 2 4 0 m R / h .

• - X MON RESPONSE FOR 2 4 0 m R / h .

.1 1

TIME OF EXPOSURE (Sac)

10

: 105 :

The response of the instrument was compared under identicalconditions with Beta-Gamma exposure-rate meter (ECIL make) andRASMION made in DRP. The response was compared at a fixedexposure-rate of 240 mR/hr while the duration of the exposure wasvaried from 5 sec to 0.02 sec The results are shown in Fig. 11.

The instrument works on four medium type Eveready batteriesand is easily portable and rugged. The advantage of the instru-ment is that the reading is held registered till reset so thatradiation levels during radiographic exposures of short durationcan be conveniently measured.

1.10 A portable microprocessor controlled instrument formeasurement of quality assurance parameters of X-raymachines

S. Kannan, M.O. Lalsare and P. Gangadharan

A microprocessor based instrument has been developed formeasurement of quality assurance parameters of X-Ray machinessuch as effective KV and esposure time. The schematic blockdiagram of the instrument is shown in the Fig. 12. Two photodiodes covered with appropriate filters are used as detectors.The short circuit current resulting from exposure to X-Rays fromthe diodes are fed to the current to voltage converter, theoutput of which is connected to an 8 channel A-D converter (I-C0809) interfaced to the microprocessor system. The microproces-sor used is the low power CMOS 146805E2 with built in RAM & I/O.The digital output is integrated over the period of exposuretime. A 4K CMOS ROM{27C32) is used for programmed storage. A 4digit LCD display interfaced serially to the microprocessorthrough I/O line.? is used for display of KV & exposure timesequentially by pressing the key "DISP. SELECT". By taking ratioof the two integrated outputs and using look-up tables in ROM,the corresponding KV will be displayed. The exposure time isobtained by starting the tiwer when the output of a photo-diodecurrent to voltage converter exceeds a 100 mV & stopping the samewhen it falls below 100 mV. The exposure time will be displayedin seconds.

The instrument is light weight, portable & it works on 4medium size 1.5V batteries (Eveready type 1035) and has a currentconsumption of 25 mA.

: 106 :

Fill LH

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F > ' g . . | 2 _ BLOCK DIAGRAM OF QUALITY ASSURANCE ANALYSER

1 -11 A mains - operated x-ray quality assurance system

A. Sankaran, N.C. Pal and V.S. Patki

A compact mains-operated up based quality assurance systemhas been developed for quick non-invasive evaluation of variousparameters of diagnostic X-ray machines such as KV-waveform, KVP,exposure time, exposure rate etc. With the entire data collectedby the unit from a single X-ray exposure, the software controlleddata acquisition system quickly analyses the data to pinpoint ifthe calibrations of the X-ray machine have since deviated. Itconsists of one pair of photovoltaic detectors and one pair ofion-chambers with differential filters and an Intel 8085raicroprocesor based data acquisition system coupled to the outputperipheral units viz. aw oscilloscope, plotter or printer. Theoutput from the detectors is fed to a divider (ratio) circuitfollowed by a sample and hold circuit and then to a precision 12-bit ADC which is interfaced to a commercially available 8085microcomputer. The data stored in the memory of capacity 5K X 8RAM are used for evaluation, display and print-out of the abovementioned parameters. Fig. 13 shows a block diagram of the dif-ferent stages of quality assurance system. Fig. 14 shows therelationship between the response ratio for differential absorb-ers and KV set on the X-ray machines while Fig. 15 illustratesthe exposures (mR) and the correct time for various timing set ona typical X-ray unit.

: 107

L 1/"•|<S/13 BLOCK OIAOHAM OK E>OSI M & I W U M A ACOUIBITIOH

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30 /.0 50 60 70 Q0 90 100 110 120 130 J40 150.

kV (-SET ON THE UNIT)

FIG.fV RATIO OF RESPONSE WITH DIFF. FILTER VskV SET ON UNIT

: 108 :

1000 j--

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F C U : 6 0 c m s

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TIME SET ON UNIT (SEC )

FIG.I5"EXPOSURE AND CORRECT TIME Vs TIME SET

ON UNIT

0.001100

1.12 Conex :

A.J. Chury and M.R. Deokar

This instrument has been designed for the measurement ofexposure rates and contamination levels due to radioactivematerials emitting beta and gamina radiations. This unit makesuse of two G.M. counters, viz., a miniature counter, for themeasurement of exposure rates, and a detachable end window coun-ter for the measuremet of contamination levels. There are fivelinear ranges of 0-2 mR/hr, 0-20 mR/hr, 0-200 mR/hr, 0-2R/hr and0-20 R/hr in the exposure rate measurement and three linearranges of 0-5 CPS, 0-50 CPS and 0-500 CPS in the contaminationmeasurement mode. The block diagram of the instrument is givenin the Fig. 16. The electronic circuit consists of a comparator,a countrate meter, an audio circuit for aural indication and an

: 109 :

electronically regulated EHT for the operation of the G.M. coun-ters. Output of the count-rate meter circuit is displayed on 50microampere panel meter, whose dial is marked in terms of mR/hras well as counts per sec. Appropriate GM counter is connectedto EHT and the input circuit, when either the exposure rater nges or the contamination ranges are selected.

( =

0-50 .A

EHT

I

BLOCK DIAGRAM OF CONEX

1.13 Alpha monitor

K.P. Raranth and P. Gangadharan

An alpha monitor for measuring very low levels of alphaactivity in the presence of beta and gamma radiations has beendeveloped. The detector part consists of a side-window photomultiplier tube and a ZnS scintillator. A perepex light guidewith a sensitive area of 36 sq.cm is used in combination with themultiplier phototube and the scintillator.

The output pulse from the PM tube are counted on a fourstage decade sealer system for time intervals of 30 sec, 60 sec,120 sec and manual, as selected by a front panel control. Theoutput of the sealer is multiplexed, decoded and displayed on afour digit LCD display. The complete electronic circuit has beendeveloped using CMOS IC's and the unit consumes about 15 mAcurrent. This portable unit works on 4 x 1.5 volt pencil typebattery cells (type 1015 Eveready make). The block diagram ofthe unit is given below in Fig. 17.

The instrument gives a background of 10 to 12 counts perhour and has an efficiency of 30 percent for alpha particles overthe sensitive area.

: 110 :

U DICDIGIT LED DISPLAY

PR03E | - IDISCRIMINATOR

+PULSE SHAPES

U STAGE DECAOESCALER* DECODERi MULTIPLEXER

, BATTERY CELLS

A x 1-5 V30 SEC.,60 SEC

S. 120 SEC,MANUAL TIMER

BLOCK DIAGRAM OF ALPHA MONITOR

1.14 Neutron flux meter

R.G. Khadke and P. Oangadharan

This is a portable, battery operated area monitor useful formonitoring thermal and fast neutron fields in terms of flux-n/cm1* sec. It incorporates a He-3 proportional counter which issurrounded by a paraffin wax moderator of thickness 35 mm. Theparaffin moderator is surrounded by cadmium sheet for absorbingthermal neutrons. The block diagram is shown in Fig. 18.

The high voltage for the He-3 proportional counter .isobtained from DC-DC converter. The detector signals afterrouting through charge sensitive preamplifer, amplifier,discriminator, are fed to a 4 1/2 digit LCD display system.Sampling time is adjusted to indicate the flux on the display.In manual operation, required when flux is very low, the countingtime is to be controlled by a stop watch. To measure thermalneutron flux the detector has to be taken out of moderator. Maxi-mum flux of 10,000 n cm ~2 sec-l can be measured. The monitor isinsensitive to gamma fields upto 15 R/hr.

: 111 :

DETECTOR

-II-CHARGESENSITIVEPRE-AMPLIF1ER

AMPLIFIER 1 DISCRIMINATOR |4-1 DIGIT LCD

DISPLAY

-t- 1250

RATr

REGULATEDPOWERSUPPLY

BATTERIES

INTEGRAL

TIMER

8 BLOCK DIAGRAM OF NEUTRON FLUX-METER

1.15 A portable neutron monitor with He-3 proportional counter

R.G. Khadke , V.H. Risbud and P. Gangadharan

This is a portable battery operated instrument useful forarea monitoring of neutron fields. The monitor incorporates aHe-3 proportional counter which is covered with perforated ad-mium cover. The monitor can be used to estimate the yirMs offast neutron sources used in several institutions and al»o doseequivalent for the neutron fields.

The detector signals pass through a charge sensitivepreamplifier and an amplifier. To stabilize the thermal neutronpeak AGC circut is used. The amplifier output signal are routedthrough a single channel analyser and a discriminator to giveoutput pulses for the neutron upto 200 keV and above respec-tively. These outputs are suitably scaled down, gated and thenfed to a 4 1/2 digit LCD display to provide Dose Equivalent. Thescaling down factors are derived using Am-Be, Pu-Be and Ra-Besources as fast neutron sources and Sb-Be source as an epithermal

: 112 :

neutron source.provided.

Nominal sampling time of six minutes is

On the bat;s of counter efficiency for the fast neutrons,the distance c= 40 cms from the counter center was selected andfields of neutroi. sources from 30 mCi to 1 Ci of Am-Be sourceshave been checked. F©r yield measurements a sampling time of 15minutes is provided. The block digram of the instrument is givenin Pig. 19.

DETECTOR

777T

+ 1250 V

CHARGESENSITIVEPRE-AMPUFIER

AMPLIFIER

+ 5Vo

DISCRIMINATORSCALING

DOWN

SINGLECHANNELANALYSER

SCALINGDOWN

GATE

REGULATEDPOWERSUPPLY

BATTERIES4x 1-5V

TIMER

4DK5ITLCD

DISPLAY

BLOCK DIAGRAM OF NEUTRON MONITOR

2. Radiation Dosimeters

2.1 Thermoluminescent dosimeter readers for health andmedical physics applications

A. Sankaran, R.S. Gokarn, A. Narayanan and A. Seethapathy

Many versions of readers for read-out of TL from phosphorsin various sizes and configurations have been designed anddeveloped. The latest in this series, Thelmedor Model 6000 TLDreader, some of which are in use in medical institutions inIndia, comprises the state-of the art development features(Fig. 20) which include cold junction compensation of thechromolalumal thermocouple junction (welded to a removablekanthal heater) using AD 595 integrated circuit; a linear

: 113 :

accurate well-reproducible temperature programmer usingcomparator-UJT oscillator-optoisolator-SCR combinations to varythe phase angle of the AC heater voltage wave form; a low leakage(75 fA) FET in^ut op-amp autoranging integrator; a glow curveextractor using an operational differentiator; a DPM to measurethe various parameters, viz., dose, EHT and heater temperature; atemperature-compensated LED as a stable check light source, etc.The reader can measure tissue doses from 0.01 cGy to 10 Gy with aprecision of better than ±2% for doses >0.1 Gy. For measurementof low doses, sealed desiccated PM tube housings, fitted with"frigistor" elements and water cooled heat sink, enable tempera-tures down to 0°C to be achieved with PM tube dark current reduc

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FIG.16BLOCK DIAGRAM OF THEIMEOORTlMt —

tion by a factor of 20 (at 1000V). A uP based reader havingadditional featurs of keyboard entry and display of variousparameters, fault annunciation, storage of glow curve and print-out facility, wide range dose measurement using both counting andDC techniques is presently under development.

2.2 Phosphor dispenser for TLD reader

H.K. Pendurkar, J.S. Nagpal

An electromechanical device is designed to dispense a fixedquantity of TL powder (around 20 mg + 0.02 mg). Three concentricmovable stainless steel discs are assembled such a way that thefunnel on the top disc holds the phosphor, the centre disc

: 114 :

collects the phosphor in a well defined groove and the bottomdisc fitted with a tube discharges the phosphor. When thedispenser assembly is subjected to electromechanical vibrationsproduced by a ceil operating on 230 V AC mains, the phosphor getsfilled in the grccv/e of the centre disc. The disc is then rotatedthrough a:! srvrle of 30° to discharge the phosphor. The dispensercan be po:. i K;..oned r.sar the drawer of TLD reader so as to directlydischarge the phosphor on to the heater tray prior to eachnitasureicer,•:.. .fn the absence of a microbalance for weighing thephosphor e-:i.-h > irr.a , this device .serves as an alternative.

2.3 k co.ua--ict_ XL .reader; _for___do_s« outjnit: measurement

U.K. P-iT.durkar, A.T. Soman, J.S. Nagpal and P. Gangadharan

A TLD Reader has been designed to measure the dose output ofteletherapy units in hospitals. A silicon photovoltaic detector-cum-FET input operational amplifier combination (EG & G HUV-4000B) has been used as light detector for thermally stimulatedluminescence of CaSO<:Dy phosphor. The 5ilicon p-n junction whenused without any external bias, operates in photovoltaic mode andgenerate* a current proportional to the light incident on theactive area (100 mm2) of the detector. The operational amplifierprovided with a fixed 200 HO feedback resistor operates ascurrent to voltage converter. It is followed by another opera-tional amplifier as integrator and a DVM display.

CaSO« :Dy phosphor (grain size 75-200 pm! is heated in aspecial tray shaped kanthal heater strip employing electricalresistance heating method. Uniform samples of mass 17.6 ± 0.02mg were dispensed directly on to the heater strip usingelectromechanical phosphor dispenser. A simple reproducibleheating programmer controls the temperature of heating profilewithin + 1°C. A 3 1/2 digit panel meter is used as displaygiving exposure directly in Gy.

The system has been tested from 0.1 Gy-2 Gy range for b0Cogamma dose with linear response. Beyond 2 Gy to 20 Gy theresponse is non-linear. The reproducibility is better than ± 5%.

The reader is compact, light weight and less expensive. Theinstrument can also be used for measurement of very high doselevels (10-i03Gy) encountered in food processing plants, radia-tion sterilization, material testing etc. Using phosphors suchas LiF, L±2B<O7 :Mn having low intrinsic sensitivity, it is pos-sible to extend tHe measurable dose to 104Gy.

The block diagram of the reader is shown in Fig. 21 and thedose versus response graph is shown in Fig. 22.

: 115 i

PHOTO DIODEOP. AMP.MODULE

HEATFILTER

KANTHALHEATERt

INTEGRATOR

TIMER ANDLOGIC

TEMP.CONTROLLER

GAINCONTROL

DPM

FIG2J. BLOCK DIAGRAM OF READER

2 V

I V

0.1 Gy 0.2 0.3 0.5 0.7 1 Gy 2 3 5 7 10Gy 20

OOSE IN Gy

FIG.S2. RESPONSE OF PHOTO-DIODE OP-AMP.

i 116 :

2.4 Photon-counting system for TL dosimeters

G. Ramanathan, R.S. Gokaran and S. Kannan

This system finds extensive use in situations where thelevel of TL output is small due to either low dose, small size orlow sensitivity of TL phosphor. A block diagram of the system isshown in Fig. 23. The system consists of two parts, a measuringhead and a photon-counting unit. The measuring head incorporatesa sliding drawer with heating facility and a multiplier photo-tube with thermo-electric cooler* The heater consists of aKanthal strip heated electrically using a proportional heatercontroller circuit incorporating a SCR and optocoupler. Theheating rate is linear and is selectable from 5°C/sec to 15°C/secand the temperature can be clamped from 250°C to 300°C. The PMtube used is selected low-noise high gain tube of the type EMI.9524S. The EHT supply for the PM tube can be varied from 500 to1500 V and has a regulation better than 0.1%. The thermo-electric cooler is used to cool the PM Tube from room temperatureto -15°C. The digital panel meter on the panel can be selectedto display either heater temperature or P.M tube temperature.The photon-counting unit incorporates a fast pre-amplifier, apulse-height discriminator, an autoranging sealer, a D to A con-verter and a 3 1/2 digit DVM with LED displays. The TL photonsemitted from the heated sample are detected by the P.M. tube andfed to the photon-counting unit. The accumulated counts during areading cycle whose time can be varied from 45 Sec to 120 Sec,are displayed after suitable prescaling of either -Jr 1 or-J-l00'from 0-10* or 0-10° counts with four decades of auto-ranging.Using this system, an integrated exposure of the order 100 u radcan be measured.

MAINS

BLOCK DIAGRAM OF TL PHOTON-COUNTING SYSTEMWITH TE COOLER

117

2.5 k microprocessor based photon counter for low levellyoluminescence and TL dosimetry

A. Seethapathy, S. Kannan and P. Gangadharan

A microprocessor (Intel 8085) based photon counter has beendeveloped for detection of very low level luminescence from TLand lyoluminescent dosimeters. The instrument incorporates anumber of features like a highly regulated (better than 0.05%)EHT for PMT wide bandwidth pulse amplifiers, fast discriminators,three independent 8-digit counter channels. 'preset time,'presetcount' and 'test' modes of operation, display of sum and dif-ference of counts in two channels and RS 232 interface for prin-ter or a p.c. The block diagram of the photon counter is shownin the Fig. 24. An eight digit 7 segment LED display is providedon the front panel tor display of the contents of one of thethree counters, 'sum' or 'difference' with suitable LED statusindicators for 'count on', 'overflow' etc. A separate 4-digitdisplay along with a numeric keyboard on the front panelfacilitates the entry of preset data and selection of mode ofoperation. The entire operation of the counter is controlled bythe microprocessor software consisting of 4 K bytes programme.This inexpensive photon counter with a pulse pair resolution ofless than 100 n sec is useful for low level luminescence studies.

F(j, BLOCK 0IAGRAM OF PHOTON COUNTER

2.6 A low power microprocessor controlled dosemeter

M.D. Lalsare, S. Kannan, M.R. Deokar and P. Gangadharan

A dosemeter, based on the latest low power microproces-

: 118 :

sor technology, has been developed for accurate measurement ofdose delivered to patients in radiotherapy centres. It incor-porates a number of features like quartz crystal-controlled timerfor exposure time measurements, auto-correction for temperatureand pressure with keyboard entry of temperature and pressure,preset time or preset dose alarm, auto-ranging, etc. Theschematic block diagram of the dosemeter is shown in the Fig. 25.A 0.6 cc ion-chamber is connected to the input of an electrometergrade operational amplifier (OPA104CM) integrator with a lOOOpflow leakage integrating capacitor. The output of the integratoris compared with the output of a D-A converter controlled by themicroprocessor for balance during the measurement of dose in ahigh gain comparator. The operation of the dosemeter includingthe entry of pressure, temperature, preset dose time, etc. arecontrolled by six keys on the panel. A 4-digit LCD display and 8LED indicators are used for indicating the dose, the dose rateand other parameters. The dosmeter has a range of 0 to 1999R intwo ranges (0-199.9R and 200-1999R) low & high, automaticallyselected by switching the gain of the input stage from 10 to 1using a high impedance CMOS switch. The dosemeter works on fourmedium size 1.5V batteries (Eveready type 1035) and has a cur-rent consumption of 25 mA.

2.7 Gammexion

A. Seethapathy and S.S. Tambe

This instrument is used for output measurement from deeptherapy and telecobalt machines and for the measurement of tabletop exposures in the case of diagnostic X-ray machines. The cir-cuit diagram is given in Fig. 26. The detector is a 0.6 cc. airequivalent ion chamber which is connected to the measuring partby means of eight metre long double braided cable. The measuringcircuit consists of a high meg resistor and a low leakagecapacitor at the input either of which can be selected for themeasurement of exposure rate or exposure respectively. Theelectrometer consists of a dual MOSFET (type MEM 955) preceding amicropower opamp. The use of dual MOSFET greatly reduces theeffect of power supply variations, temperature effect etc. Theranges of the instrument are 5 R/min to 250 R/min and 5 R to 250R in three ranges. The accuracy of measurement is within ± 5%.Build up cap for the chamber is provided for use with Co-60radiation. This instrument operates on four 1.5 V pencil typebatteries.

t 119 :

146805

CMOS DPSYSTEM

l/o

l/o

INT

1 11 1

LCD

-i n n_i i i i i

DISPLAY

O

a

o

EXP.U.CEXPEXP HAIE

TIME

o r SET EXP'I•a TRESSUHEo TEMP.oC. F

PANEL CONTROLS

0 - A

D.C.AMP.

10 PPS

CLOCK

COMPARATOR

RANOE

IONCHAMBER

ANOE t DISCI lATIOt

Ft$-> 4 5 " BLOCK UIAUI1AM OP DOSE METER

2 6CIRCUIT DIAGRAM OF GAMMEXION

: 120 :

2.8 Portable digital dosemeter for beam output measurements

A. Sankaran, V.S. Patki and P. Gangadharan

A portable digital dosemeter is developed for calibration attherapy dose levels of telegamma equipment and high energy ac-celerator. The block diagram is shown in Fig. 27. The detectoris a small 0.5 cm3 air equivalent chamber coupled by 25 m longcable to a feedback operational type electrometer (OPA 104,leakage current : 75 fA). The output of the amplifier is fed toa bipolar digitl panel meter with LCD display available in-digenously. It can measure dose and doserates in two ranges,i.e. 0-2 Gy <Gy min-*) & 0-20 Gy (Gy min-*) with a precision of± 0.1%. A programmable crystal oscillator (PXO 600) serves as aprecision timer for dose measurement. Two settings of polarizingvoltage with dual polarity is provided for accurate photon andelectron beam measurements. All the requisite voltages for theelectrometer amplifier {+ 15V), ion chamber (± 180V) and DPM (9V)are obtained using DC-DC converter. The whole circuit is ener-gised by either four 1.5 volt flashlight cells or AC mains. Thedosemeter is calibrated against transfer standards and thecalibration accuracy is within ± 2% for the energy range of 30keV -1.3 MeV.

v.. .. . J

FID- 2-7CiHCuir BLOCK OMOKAM DI-' OOSEMETER

: 121 :

2.9 A compact wide range radioisotope calibrator with digitaldisplay using an air-equivalent Re-entrant chamber

A. Sankaran and R.S. Gokaran

This instrument combines a 400 cm3 re-entrant air equivalent-r.yr.'.br.-r. and a measuring part comprising a MOSFET electrometer, a Vto F converter and a variable time-base. Activities in the rangeof 100 KBq-40 GBq ojf gamma -emitters (30 keV - 3 MeV) in variousconfigurations can be measured within 2 sec with a chamberpolarising voltage of only 60 V. The precision is ± 1% do) downto an activity of 4 MBq { = - 100 uCi) of '"Cs. By setting thegamma constant of radionuclide, an overall accuracy of ± 5% canbe achieved.

2.10 A up based water phantom dosimetry_system for. radiationfield analysis of »°Co and accelerator beams

A. Sankaran, A. Narayanan, N.C. Pal and K.G. Vohra

This system was developed for dose distribution measurementsin a tissue equivalent medium, exposed to *°Co and acceleratorbeams. The block diagram of the system is shown in Fig.28. Itcomprises a 40 cm3 perspex water phantom inside which a 0.1 cm3

ionization chamber or a miniature p-i-n diode can be moved in aXY plane by stepping motors and positioned at any point to a spa-tial resolution of ±0.1 mm. A transport carriage with waterreservoir and pump makes the set-up of the phantom quick andeasy. The ratio of currents from one of these detectors to areference detector is fed to an A/D converter. An optional com-pact film densitometer, designed using a LED as the light sourceand silicon photovoltaic light detector, mounted in a framedriven by the same motors (Fig 29) extends the use of the systemto scan the density of the processed film for radiation fieldanalysis. Fig. 30 shows the block diagram of the densitometercircuit. The provision of control signals to the motors and ac-quisition of data are achieved by using the uP. The XY detectorposition and the dose or density data are displayed on the in-strument. The microcomputer is interfaced to a teleprinter.Various beam parameters such as CADD, dose profile, penumbra aredirectly provided on the XY recorder with the facility of prin-tout of dose matrix. Isodose curves can be constructed by usingthe method of decrement lines. The plotting accuracy is ± 1% orbetter. The optical density range is 0-3.5 (linear) with aresolution of ± 0.01 density. Maximum area scanned on film is 27cm x 30 cm.

t 122 t

1MMAPERTURE

IEOON

M.ED 'FILM(5062-1400)

pVD-OA ^ / T(HUV-iOOOJ J f l i

•-1 — r s*-'

ZOOM

2SET ZERO

; V M i i «

—)(—

r1

OA-I

, T

L.

---! ,

IK OA-2

PiSET

DENSITY

J O CJ.l-I I-

R;

UVCOBDEBOUTPUT

v ' "-« -,„- *•s'

^- OlOlT 0 PM

FIG.2.8 BLOCK OIAGRAM OF OENSITOMETER CIRCUIT

LIGHT TIGHT.MOUSING

IQI' Al PLATE

SPACER

4 01. ASS PI ME -C0UP1FD ' 0Y SCREW i»

M DML.V ASS I'LATC

-fiiafiWAM MOf T(I'.(.AIE

. l ' ) A^SFMBIY OF FILM DENSITY r,CA

: 123 :

I F l t I'HIMIEH

PUNCH READWPAPEH TAPE»'

At.FRAME FI*ED/-GLASS PIATF. I flT"7n—3- ... I nT~=i—=71ON PHANTOM-j / (FILM MOUIIT) | l j B B.LI | I l l • 5 ) |

-PVD-OA I U 0 5 e n A T E UENSITY

Own J I—[LOG.AMP]c nr OISPLAY

COUPLINOTO V SCREWOF STEPPING / RECTANOULAHL _ _fOTOP A.RD PLATE

MOUSINGFIG.30 BLOCK DIAGRAM OF RADIATION FIELD AHAlVSfeR

200

* TEFLON SOCKET

*a i4-4;'K Cn o 5 mm u i D g MESH DIMEUbiON

F1G.3) CUT-AWAY VitW OF X-HAf TRANSMISSION CHAMBER

: 124 :

2.11 X-ray transmission ioni_sa_t_ipn_ch_amber dosemeter forpatient dos e_ me as urement i n d; i ajgno st_.ic _radi pi. 9. g_y

A. Sankaran and V.S. Patki

The largest man-made radiation dose to the general popula-tion comes from routine medical x-ray diagnostic procedures.With view to reduce the patient dose in diagnostic radiology,the total dose to the patient should be measured accurately.This instrument was developed for this requirement. Fig.31shows the cut-way view cf the X-ray transmission chamber designedto measure the air Kerma/ cm2 of beams used in radiography andfluoroscopy. The need for light transparency and electrical con-ductivity of the chamber has been m«t by constructing theelectrodes out of RF screen (metal coated nylon mesh). Threesuch parallel mesh electrodes (16 cm x 16 cm) tightly stretchedbetween bakelite frames and insulated from each other,(electrode/gap length : 10 mm) constitute the chamber with a sen-sitive volume of about 510 cm3 . The current of charge from thechamber over a wide range is measured by a digital varactorbridge electrometer. Detailed investigations on the characteris-tics of the chamber such as saturation, sensitivity, energy de-pendence (50 kV - 150 kV) response for different radiation fieldarea, uniformity of response of the chamber, effects of distanceand long term stability have been carried out. The chamber meetsall the varied requirements and can measure the incident patientdose with an overall accurcy of ± 11%. The chamber can be eithermounted on the housing of the light beam diaphragm of the X-rayunit or used as a stand-alone system with an image intensifier -TV monitor.

3• Personnel Monitoring Instruments

3.1 An Optical densitometer compatible with a personal computermonitoring

R.N. Das Sarma, H.K. Pendurkar, A.K. Pathan and U.P. Gaonkar

The instrument has been designed primarily to provide alinearised voltage with respect to optical density of processedpersonnel monitoring films for computation and assessment of dosedue to & X and r radiations using personal computer.

The circuit utilizes a photomultiplier (RCA type 1 P21)whose anode current is kept constant by varying dynode voltageelectronically. A suitable fraction of dynode voltage change, aquasilogarithmic function with respect to optical density, islinearised using a biased diode network. A tungsten lamp (6V,9W) powered by a highly regulated DC supply serves as the light

t 125 i

source. An amplitude modulated DC/DC converter using UJT and J.K.flip/flop square wave generator serves the purpose of obtainingvarying voltage with respect to anode current. The instrumentmeasures diffuse optical density upto 4 with a least measurabledensity of 0.01. The calibration of the instrument has beenchecked against optical density of ASA standard and has beenfound agreeing within ± 1%. The block diagram of instrument isshown in Fig. 32.

VOLTAGECONTROLLEDDC/DC

CONVERTER

TO AOCAND COMPUTERINTERFACE

BLOCK DIAGRAM OF OPTICAL DENSITOMETER

3.2 Solid state digital optical densitometer

R.N. Das Saris*?., K. Aravindakshan, H.K. Pendurkarand P. Gangadharan

A digital transmission densitometer has been designed formeasurement of optical density of personnel monitoring films.The instrument incorporates a very low noise photovoltaic detec-tor with built in FET input operational amplifier (EG & G typeHUV-4000 B). The log output of the detector in the photovoltaicmode after transmission through a sample film, is made linearusing one of the dual matched monolithic transistor LM 114 as log

: 126 :

element in the feedback loop of the FET input operationalamplifier. By this method the linearity of the output voltagewith respect to optical density has been achieved. Temperatureeffect of the log element has been eliminated by providing afixed offset to compensate the emitter-base turn-on voltage ofthe log element. A simple low cost and reliable digitalvoltmeter with 7 segment LED has been designed to display theanalog output in the digital form. An LED is used as a lightsource in the transmission system of the instrument. The instru-ment covers a density of 0-3 with a resolution of ± 0.01 O.D.Using a miniature tungston filament lamp powered by a highlystabilised D.C. power unit as a source of light, the instrumentcan cover density range of 0-4. The spectral distribution of thelamp is suitably matched to the spectral response of the detectorby using an optical filter. An infra-red absorbing filter isused to avoid thermal noise reaching the detector.

The calibration of the instrument has been checked with dif-fuse density of ASA standards. The block diagram of the den-sitometer is shown in the Fig. 33.

FILM (1-D)

LIGHTSOURCE

E : VOLT

D : DENSITY

LOG. AMR r

OPTICALASSEMBLY

ADC

*"DETECTOR 1

DIGITALDISPLAY

E 2 = 1 -LOG 1 0 E, = D

F -33 BLOCK DIAGRAM OF SOLID STATE DENSITOMETER3.3 A microprocessor based film dosemeter reader

H. Mittal, R.N. Das Sarma, K. Aravindakshanand P. Gangadharan

The microprocessor based semiautomatic film dosemeter readerhas been designed and developed and measures optical density ofthe processed monitoring film at its six different filter posi-tions and assesses dose due to X, 3 and gamma radiations.

The system subroutines and the evaluation of doses, in therequired format, are developed using INTEL-8085 Central Process-

$ 127 :

ing Unit. In the printout, a 36 character space is provided forinsertion of either the name of the person (for despatch toinstitution) or the optical densities (for office use) asdesired.

The entire operation of assessment of dose including print-ing but excluding film placement and badge data entry time takesabout 10 seconds for each film. The block diagram of the Tteaderis shown below in Fig. 34. The instrument is provided with threemodes of operations viz. "CAL" (for calibration), "CONTROL" (forcontrol film) and "NORMAL" (for usual monitoring films).

The"RESET" switch is provided with the reader exclusivelyfor re-entry of film data through key board.

The system is operable on any of the three functional modes,mentioned above, except that the "control" mode is required to beselected before "Normal" mode for every institution.

KEY BOARD

DENSITOMETER

MODE SELECTION

1. CALIBRATION

2- CONTROL

3- NORMAL

ERROR MESSAGES

DOSE/DENSITY DATA

PRINT OUT

: 128 :

3.4 TLD badge reader

R.N. Das Sarma, H.K. Pendurkar, A.T. Soman, A.K. Pathan andShiv Kumar

This instrument is specially designed for routine personnelmonitoring and meets the requirements of reading three identicalTL discs fixed on a metallic card. The reader provides areproducible heating profile to TLD, senses the TL signal by aphotomultiplier tube (PMT) and displays the total integrated TLoutput in terms of Roentgen (R) on a 3 1/2 digit (2V, FSD) panelmeter. The main features of the instrument include wide coverageof dosimetric range (1000R), auto read-out cycle (60 sec), digi-tal display for high voltage supplied to PMT(volts), heatertemperature (°C) and radiation exposure (R). The block diagramof the reader is given in Fig.35

Fail-safe interlocking operations, simple to use, easyportability and servicing make the instrument suitable forroutine monitoring purposes. During the period (1982-86) a totalof 25 TLD readers have been fabricated and are being used atdifferent centres of the country including the Division. Two TLDreaders have been supplied to National Councl of ScientificResearch, Lusaka, Zambia in 1984.

DIGITALDISPLAY |

SELECT DISPLAY)

ITEMP

_ tEHT EXP/CAL

t

I HV POWER SUPPLVk |BG SUPPRESSION! . (DIFFERENTIATOR)—r~ RECORDERI , '"" ' j I . | . T ~ , (GLOW CURVE)

I • t • |

II

RECORDER(TEMP. PROFILE)

TIME

LV POWER SUPPLY |

FUNCTIONAL BLOCK 01AGRAM OF THE READER

: 129 :

3.5 Heater system for TLD badge reader with cold junctioncompensation

R.N.Das Sarma, H.K. Pendurkar, A.K. Pathan

One of the most important factors for obtaining areproducible TL read out system is its heating system. With therecent availability of an IC clip (AD 595) having a build-up coldjunction compensator, the heater system of the existing TLD BadgeReaders has been redesigned. The block diagram of the heatersystem is as in Fig. 36. A specially designed saturable corereactor chocks backed by a thermocouple (K-type) feedback controlcircuitry maintains the reproducibility of the heating profilebetter than ± 1%. The system is being incroporated in newlyfabricated TLD readers.

THERMOCOUPLE

AD 595

HEATER 3^-DIGIT DPM

I MAINS.230V, 50 HZ

f HEATERI TRANSFORMER RECORDER

SATURABLECORE REACTOR

COMPARATOR

a.I 200a| 100

20 40 60 60TIME, Sec.

'36FUNCTIONAL BLOCK DIAGRAM OF HEATER SYSTEMWITH COLD JUNCTION COMPENSATION

3.6 An improved semiautomatic TLD badge reader

P. Ratna, S. Kannan and P. Gangadharan

A microprocessor controlled TLD teader with semi-automaticfeatures has been developed for processing the TLD badges, based

: 130 :

on Intel 8085. The yeader has a mechanical arrangement con-trolled by a stopper motor wherein the three TLD discs on the TLDcard are automatically read one by one, the dose calculatedaccording to a predetermined empirical formula and stored in abattery backed memory for transfer to a PC later. The glowcurves of the three discs are also stored in the memory and canbe recalled on a 16 x 26 LED matrix on the panel. The blockdiagram of the Yeader is shown in the Fig. 37. The current fromthe PM tube which is proportional to the TL output from thedosimeter is fed to an I-F (current-to-frequency) converter withan auto-zero feature under microprocessor control for cancella-tion of dark current, zero drift, etc. The EHT applied to thePMT is programmable by the microprocessor for gain control. Theoutput from the I-F converter is gated into a microprocessor com-parable counter (8253) interfaced to the microprocessor system.A Hewlett Packard 16-digit alpha-numeric display system (HDSP-8716), used for display of TLD readings, dose data, EHT, tempera-ture, etc. Two dedicated bar-graph displays indicete the heatertemperature and EHT outside the microprocessor control, toprovide a direct indication of the healthy operation of thesystem. The front panel controls and 16 xl6 LED matrix for glowcurve display are interfaced to the system through a programmablekeyboard display controller I.e. (8279). The front panelcontrols include a numeric keyboard for entry of data likecalibration factor badge number, background etc. and "start","stop" controls for the operation of the reader. The compactmicroprocessor system consists of Intel 8085 CPU, 8 K ROM forprogram storage, 25 byte battery backed RAM (5101) for datastorage & two I/o devices (8155). The software consists of 8k-bytes of programme Including expensive diagnostic routines. Thereader has a measurement Yange of 1 mR to 103R with auto-rangingfacility.

HEATERCONiriOl

I ALPli* I I OlOW II iiuMr.mc CUIIVE| PISPIAY [ | DISPLAY |

FCIQHTPAHH

; 01(1 HOIS

BLOCK DIAGRAM OF TLD READER

: 131 *

3.7 A pocket type thermoluminescent personnel dosimeter

K.G. Vohra, J.S. Nagpal, H.K. Pendurkar and P. Gangadharan

A pocket type thermoluminescent dosimeter has been developed{Fig. 38) based on CaSO<:Dy phosphor. A plastic moulded holderwith a clip, in the shape of a fountain pen has been used as thecontainer for two dosimetric elements. The dosimetric elementsare inserted in a plastic tube and this tube, in turn, is coveredby a cylindrical filter of 0.5 mm thick lead having 1 mm 0 per-forations providing 10% opening to the direct radiation. The

• M M l VCAPILURIES

>=—ncni PORTION ' n ^ n _ '-CAPILLARY / r , p

. . I'S'LAY OF '•PeRFORATED HOLDER C A P

ICES" ?:CATION NUMBER L E A 0

TYPE THERMOLUMINESCENT DOSIMETER

filter brings down the overall response of the phosphor in theenergy region 60 keV-200 keV but the reduction for lower energiesis far more. Overall response of the system is within ± 10% overthe range 30 keV - 1.25 MeV. The elements consist of selectedglass capillaries containing sealed and preweighed fixed mass ofCaSO«:Dy phosphor. The elements show a linear response in therange 2.58 x 10-• - 2.58 x 10-» C.kg~» (10 mR-lOOOR). Elementsare read using a conventional TL reader and can be reused over anumber of cycles after giving a simple annealing for 20 min at400° C.

4. Miscellaneous

4.1 Dosimetry of non-ionising radiations

J.S. Nagpal, Geetha Varadharajan and P. Gangadharan

Dosimetry of UV radiations, in practice, is done using ther-mopile, optoelectronic detectors and chemical actinometers.Thermoluminescent phosphors were studied for intrinsic UVresponse and PTTL response.

The phosphors CaO:Dy, CaSO«:Dy, CaSO<:Tm, CaFa:Dy, Al2O3(Si,Ti), Mg2SiCU:Tb and MgO have good intrinsic UV response(Table 1) but it is a function of the temperature during UV ex-

: 132 t

posure (Fig.39) and the radiant flux (Fig.40) unlike the case ofgamma - exposures where the TL response is observed to be doserate independent.

Microwave radiation produces thermal detrapping of thecharge carriers from energetically 'Shallow1 traps in variousgamma irradiated TL phosphors. Reduction in the integrated TLoutput of BaSO<:Tb is proportional to the microwave radiant ex-posure {product of the irradiance level and the exposure time) in

Intrinsic UV responseof various phosphors as a functionof the temperature during exposure.(l)CaSO4:Dy (0.1 wt%),

(2)CaSO4:Tm(0.<» wt%),

(3) A12O3 (Si, TI), (4) Mg2SiO4:1b,

(5)CaSO4:Dy (0.05 %

Dependence of intrinsic responseof the phosphors on UV radiant flux.(1) CaSO4:Dy (0.1 wt%), (2) MgO,

(3) CaSO4:Tm (0.05 wt%), (4) AlgOg (Si, Tl),

(5)TLD-200, (8)Mg2S10^ Tfc.,

(7) CaO:Dy (0.1 wt%). Radiant energy

raOant flu* (Jnf1 s'J) — 2.16xlO"4 J Fty

the range 250-2000 W.nr8 (Fig.41 and 42). A single function canrepresent the microwave induced reduction over the irradiancelevels for various intitial gamma exposures 2.58 x 10"3 - 2.58 x10-4 C.kg-* {10-10-3 R ) . Thus TL phosphors can be used, withcertain limitations, for UV and Microwave Dosimetry.

t 133 t

INTRINSIC RESPONSE OF TL PHOSPHORS TO 254 am UV

Phosphor Activator Procured from <Activator Procured fromconcentration

RelativeResponse*

CaSO4:DyMgO

CaSO4:TmAl2O3(Si, Ti)

0.1 mol %

CaFp:Dy(TLD-200)(900 C-lh* treated)

0.05 mol #10 ppm Ti300 ppm Si

0.001 gin-atom/mol Tb

DRP, Trombay 1.0Norton Research Corp. 327(Canada) Ltd.DRP, Trombay 80HP Division, Trombay 35

Harshaw Chemical Co.. 308U.S.A.Dai Nippon Toryo Co. 405Ltd., Japan

• Baaed" oa 2 min exposure at 30-cm distance from a 36 W P«n RayLamp Radiant flax « 0.11 Jm S~l).

100 •

75 -

| SO

2%

I 1 °

!A

h-15

L- j\

E«poiun 'imp (nm)ot 500 W «••'

30

100 200

7/ TjfTemp«roturi \'\\

jfi'ical n . jflitw curves of ttnmniii irruiiulcdBaSO4:Tb after various microwave cxpoturci «l500 W m 2 .

Microwattirrodignct(W«-»l

ISO

2S0

II. output of y-lrrMliilcdBaS()4:Th on cxpoturc lo tnicrowtve radiation atilillercnl irrntliance levcli.

WO 150

l i n t Inm)

134 :

4.2 X-ray excited optical luminescence studies of rare earthactivated thermoluminescent phosphors

J.S. Nagpal and M.J. Kamat

X-ray excited optical luminescence (XEOL) in rare earth ac-tivated phosphors is generally attributed to the interaction ofprimary incident X-ray photons with host atoms producing a largenumber of density of secondary excitants which have a greaterprobability of eventually exciting the luminescence of the rareearth ions. XEOL of TL phosphors CaSO4, MgFa:Dy and CaO:Dy wasstudied at RT to determine the emission spectra and characteris-tics of the emission centres for a possible inference regardingthe charge state of the rare earth ion. XEOL spectra of CaSOi:Dy,MgFt:Dy and CaO:Dy are typical of Dy3* and similar to that of TLemission spectra, (figs,43,44,45) However, the studies failed toreveal the charge conversion state of the RE ion, on irradiation,minor difference, as regards the intensity ratio of various linesare observed, depending upon the host matrix and the radiationhistory.

500Woveleitgm Inml

X E O L spectrum o f C a S O < : D y at RT CO 25 Cj.

600Wovok-ngth {nml

XI:<1| . |>O.IM ol t\<O.I>> ul KT (20 - 2 5 V). (A)lialul (H) -/-irrailtiilvil (2..1 x lO^Ciy) atui ( I t

•/•irrailialcii (7.5 x (O'CJy).

XI-OI. spectra (A) < a ( ) : l ) y (II)CO IS O .

at KT

: 135 j

4.3 Thermoluminescence of magnesium oxide and its trappingkinetics

J.S. Nagpal and S.P. Kathuria

Pure MgO crystal (Nortor USA) containing Fe, Cr as inherentimpurities was examined for UV and gamma response. It exhibitsTL glow peaks around 88, 150, 172, 195 and 250°C (heating rate55°C min~1). The most intense peak is around 88°Qj but its postirradiation stability is very poor. On storage at RT itself (20°- 25°C) it fades away completely within a week.

For gamma irradiations, the integrated TL of MgO is linearlyproportional to the r exposure in the range 5 x 10-« C.Kg-1 tolC.Kg-1 and supralinear upto 50 C Kg-1. It is sublinear forhigher exposures.

The phosphor exhibits significant intrinsic response to 365nm photons (3.4 *V energy). Phosphor has high intrinsic responseto 254 nm photons (4.88 eV) but the absolute TL sensitivity perunit radiant energy is a function of the UV radiation intensity.

Activation energy E of the 88°C glow peak was determinedusing two methods (i) initial rise method of Garlick and Gibsonand (ii) peak shape method of Chen. Kinetics was observed to beof second order for the 88°C peak, using the isothermal decaymethod^ Fig. 46.

Otcoy timt ( mm )

\CL> V 6 p l o l s of /"••*" " vs decay lime for y irradiated MaOmaintained isothennally al 85"C.

; 136 :

4.4 Checking the uniformity of emulsion coating on medicalx-ray films by low energy x-ray transmis.sion__techuiigue

A.V. Lakshmipathy, M.J. Subramanya and P. Gangadharan

In diagnostic radiology, medical X-ray films used shouldhave uniform emulsion thickness in order to get proper data onthe diagnostic information sought. For checking the uniformityof emulsion thickness X-ray films, XRF technique and Antimony KX-ray transmission technique have been reported. XRF techniqueinvolves the use of complicated instrumentation. Antimony K X-ray technique lacks in senstivity as the attenuation in the An-timony K X-ray beam caused by the emulsion of X-ray film is rela-tively small compared to the titanium K X-rays. For example, 4.5mg/cmz of emulsion would attenuate antimony K X-ray beam by afactor of 1.1 whereas the titanium K X-rays would get attenuatedby a factor of 8. Hence, H-3/Ti Bremsstrahlung source was usedas a source of Ti K X-rays. An end window GM counter withsealer-timer was used for measuring the intensity of Ti K X-rays.A collimator with an aperture of 3 mm diameter was used withsource assembly to enable scanning of films. Undeveloped Kodakcrystallex, Agfa-Gevaert Dj & D* of size 30 cm x 30 cm werescanned. Only in case of crystallex film, non-uniformity couldbe observed. The uniformity of the base of the film could beverified by scanning after developing the film directly in fixersolution. This indicates that the emulsion thickness could benon-uniform. The studies therefore indicate that low energy X-ray transmission techdnique using H-3/Ti bremsstrahlung sourcecan be used for checking the uniformity of emulsion thickness onX-ray films.

4.5 Assessment of radiation exposure to a non-radiation workerin an industrial radiography source transport accident

A.V.Lakshmipathy, B.K.S. Murthy, Geetha V. andP. Gangadharan

A non-radiation worker got exposed to Ir-192 gamma rays froma radiography source pencil in an accident during transport ofcontainer with source pencil from one radiography site toanother. Dose calculations were made taking into account the ac-tivity of the source, the duration and the geometry of exposureconditions. The problem of dose assessment was complicated bythe varying distance of source from the body surface, lack of in-formation about exact duration of exposure in different positionsetc. Dose estimates were done considering the above factors.Experimental measurements simulating the exposure conditions weremade to arrive at dose distributions at different depths in thethigh and to assess the dose to the bone. A thigh phantom of

: 137 :

tissue equivalent material and thermoluminescent dosimeters inthe form of CaSCU :Dy powder were employed in the simulationstudies. Appropriate correction factors were employed for theenergy dependence of the dosimeters for the primary and backscat-tered gamma rays from Ir-192. The doses to different regionsranged from 500-11,500 rads. Dose estimates correlated well withthe clinical findings.

4.6 Facility for calibration check of radiation monitoringinstruments

M.J. Subramanya, A.V.L. Pathy and B.K.S.Murthy

A radiation exposure facility for calibrating radiationmonitoring instruments over a wide range of exposures withoutchange in geometry has been fabricated. This facility has a 430millicurie Caesium-137 source fixed on to a rotatable sphere, ina radiography camera. The sphere can be rotated to bring thesource from safe position to exposure-on condition. It has a 2.5cm diameter collimator and three lead absorbers in front of thecollimator. These absorbers, single or in combination can bebrought into the beam to obtain different exposure rates in therange 5 mR/hr to 1.5 R/hr at 30 cm from the source.

A similar facility was fabricated with a 5 millicurieCaesium-137 source for checking the response of radiationmonitoring instruments. This facility has a narrow collimator of5 mm height and 20 mm width. The source is brought to exposureposition by lifting a rod containing the source. The monitoringinstrument can be placed at 5 cm or 10 cm distance from the edgeof the collimator. A facidlity of this type was supplied toRadiation Protection Services, Zambia.

4.7 Radiological .monitoring of diagnostic X-ray installations —a correction for change in spectrum

R.R. Vishwakarma

The monitoring of diagnostic X-ray installations from radia-tion protection standpoint involves the measurement of radiationexposure rates due to X-rays scattered by patients and otherobjects in the vicinity. The energy of X-rays reaching themonitoring instrument is significantly altered due to absorptionand scattering by the intervening material. Consequently, theresponse of the detector of the monitoring instrument alsochanges accordingly.

The direct spectra due to X-rays of different kVp from aTRIDORSty diagnostic X-rays have been measured with a scintilla-tion spectrometer having a 3 mm thick Nal (Tl) detector. As the

: 138 :

photon fluence in the direct beam is very high, the beam scat-tered at an angle of 90° by a thin mylar film has been used formeasurement. Assuming a (1+COS2©) distribution for coherent andincoherent scattering, the observed spectrum is correlated withthe incident spectrum by appropriate mathematical expression.The spectra scattered by a mix D phantom and the materials in thevicinity were measured and taken as the representative scatteredspectrum. For these, the effective energies were determined bydetermining the effective absorption coefficients. The effectiveenergies of the scattered spectra thus evaluated and the cor-responding correction factors for typical ionisation chambersurvey meter are given in the following table 2.

Table 2. Effective energies and correction factors forion-chamber instrument.

KVp Effective energy of scattered Correctionsetting X-rays at control panel factor

KeV

40 16 1.8060 18 1.5580 19 1.43

100 24 1.05120 27 0.90

PUBLICATIONS

1. Measurement of backscatter & transmission factors for betarays using thermoluminescence dosimeters, B.K.S. Murthy andJ. Bohm, Radiation Protection Dosimetry 2,2 (1982) 63.

2. A portable instrument for the determination of peak voltageof a diagnostic X-ray machine, S. Kannan, A.V.L. Pathy and P.Gangadharan, AMPI Symposium, Coimbatore (1982).

3. Use of preheat facility in TLD readers, B.K.S. Murthy, AMPIsymposium, Coimbatore (1982).

4. Radiation accidents with remotely operated radiographyequipment, A.V.L. Pathy, B.K.S. Murthy, V.G.R. Subramanianand P. Gangadharan, IARP, Annual Conference, Kanpur (1982).

5. An unusual radiation accident with gamma radiographyequipment, M.J. Subramanya, IARP, Annual Conference, Kanpur(1982) .

6. Contribution of leakage radiation from source housing to thepersonnel dose of industrial radiography workers, R.R.Vishwakarma, A.V.L. Pathy, M.J.Subramanya and P. Gangadharan,IARP Annual Conference, Kanpur (1982).

: 139 t

7. External accident dosimetry capabilities & limits, P.Gangadharan and B.K.S. Murthy, Invited lecture in IAEASeminar on Radiation Emergency Preparedness. Lublijana,Yugoslavia (1982).

8. Emergency planning in India, P. Gangadharan and A.V.L. Pathy,Invited lecture in IAEA Seminar on Radiation EmergencyPreparedness, Lublijana, Yugoslavia (1982).

9. Internal accident dosimetry capabilities and limits,P. Gangadharan and A.V.L. Pathy, Invited Lecture in IAEASeminar on Radiation Emergency Preparedness, LublijanaYugoslavia (1982).

10. Accident experience in industrial and medical uses, P.Gangadharan and M.J. Subramanya, Invited lecture in IAEASeminar on Radiation Emergency Preparedness, Lublijana,Yugoslavia (1982)

11. A preliminary study of the TL phosphors as doaemeters formicrowave radiation, J.S. Nagpal, Geetha Varadharajan and P.Gangadharan, Phys. Med. Biol. 27 (1982) 145.

12. Thermoluminescence of rare earth doped BaSO« phosphors andits applications, J.S. Nagpal and Geetha Varadharajan, Int.J. Appl. Radiat. Isot., 33, (1982) 175.

13. A priliminary study of thermoluminescent phosphors asdosemeters for microwave radiation, J.S. Nagpal, GeethaVaradharajan and P. Gangadharan, Phys. Med. Biol. 27 (1982)145.

14. Microwave dosimetry using TL phosphors, J.S. Nagpal, G.Varadharajan and P. Gangadharan, 5th Conference onMedical Physics, Coimbatore, Jan., (1982).

15. A solid state digital optical densitometer, R.N.Das Sarma, K.Aravindakshan, H.K. Pendurkar and P. Gangadharan, 5thConference on Medical Physics, Coimbatore (1982) 3.

16. A compact wide range radioisotope calibrator with digitaldisplay using an air-equivalent reentrant chamber, A.Sankaran and R.S. Gokarn, Int. J. Appl. Radiat. Isot. 33,(1982) 341.

17. Microwave dosimetry using thermoluminescent phosphors, J.S.Nagpal, Geetha Varadharajan and P. Gangadharan, 5thConference on Medical Physics, Coimbatore, Jan., (1982).

18. Radiation monitoring equipment kit for the surveillance ofloading operation and handling radiation emergency inhospitals, M.R. Oeokar, V.H. Degwekar, S. Kannan, K.C. Bajajand S.B. Joshi, 5th Annual Conference on Medical Physics,G.K.N.M. Hospital, Coimbatore, (1982).

19. A portable alpha monitor for instant checking of leakagefrom radium needles. K.P. Karanth and P. Gangadharan, 5thAnnual Conference on Medical Physics, G.K.N.M. Hospital,Coimbatore (1982),

20. A portable neutron flux meter, R.G. Khadake, V.H. Degwekarand P. Gangadharan, 9th IARP Conference, Kanpur, Feb. (1982).

t 140 t

21. A microprocessor controlled water phantom dosimetry systemfor radiation field analysis of Co-60 and accelerator beams,A. Sankaran, A. Narayanan and N.C. Pal, 5th Annual Conferenceon Medical Physics, Coimbatore, (1982).

22. Some studies on electron and photon dosimetry usingthermoluminescence dosimeters, B.K.S. Murthy, Ph.D. Thesis,Bombay University (1982).

23. A microprocessor controlled TLD reader for processing the DRPpersonnel monitoring TLD badges, S. Kannan, A.K. Oberai andP. Gangadharan, 10th Annual Conference on RadiationProtection, BARC. Bombay (1983).

24. state of art in neutron soil moisutre gauges, A.V.L. Pathy,Invited lecture in Workshop on Isotope Applications inHydrology, Pune (1983).

25. A compact reproducible solid state linear temperatureprogrammer for TLD applications, A Seethapathy & A.Sankaran, Health Phys. Research Abstracts, IAEA/HPRA/10,Vienna (1983).

26. Non-ionising radiations - hazar^a, protection and dosimetry,J.S. Nagpal, Geetha Varadharajan and P. Gangadharan, 6thAnnual Conference on Medical' Physics, Srinagar Oct. (1983).

27. A system flow-chart of a micro processor controlled semiautomatic film dosemeter reader for personnel monitoring,R.N. Das Sarma, H.O. Mittal and P. Gangadharan, Radiat.Prot. Dosi. 5, (2) (1983), 131.

28. Kinetics and trapping parameters of TL in Nal (Tl) and MgO,J.S. Nagpal, S.C. Sabharwal and S.P. Kathuria, NationalSymposium on Theory and Practice of TSL and Related Topics,Ahmedabad, Feb. (1984).

29. Radiometric techniques in personnel monitoring filmdosimetry, A.V.L. Pathy, B.K.S. Murthy, M.J. Subramanya andP. Gangadharan, Int. Conf. Applications of Radiation onIndustrial Development (ICARID), Bombay (1984).

30. A beta transmission gauge for measurement of sheet thickness,H.O. Mittal, A.V.L. Pathy, M.J. Subramanya and P.Gangadharan, ICARID, Bombay (1984).

31. A suggested method for checking the uniformity of emulsioncoating on medical x-ray films, A.V.L. Pathy, M.J. Subramanyaand P. Gangadharan, IARP Annual Conference, Jodhpur (1984).

32. Protection monitoring of high energy installations, A Noteof caution, B.K.S. Murthy and P. Gangadharan, IARP AnnualConference, Jodhpur, (1984).

33. Radiological monitoring of diagnostic X-ray installations,A correction for change in spectrum, R.R. Vishwakarma,IARP, Annual conference, Jodhpur (1984).

34. X-ray excited optical luminescence studies of rare earthactivated thermoluminescent phosphors, J.S. Nagpal and M.J.Kamath, Int. J. Appl. Radiat. Isot. 35, (1984) 141.

j 141 :

35. A programmed radiotherapy microcomputer, N.C. Pal, S. Kannanand P. Gangadharan, IX Annual Conference of Medical Physics,Calcutta (1984) (Abstract).

36. A digital contamination monitor for assessment of low levelbeta and gamma contamination, K.P. Karanth and P.Gangadharan, 7th Annual Conference of Medical Physics, CancerCentre & Welfare Home, Calcutta (1984).

37. Thermoluminescence of magnesium oxide and its trappingkinetics, J.S. Nagpal and S.P. Kathuria, Int. J. Appl.Radiat. Isot. 35 (1984) 495.

38. A microprocessor controlled medical dosimeter, S. Kannan, A.Seethapathy, and P. Gangadharan, Eleventh Annual Conferenceon Radiation Protection, Defence Laboratory, Jodhpur (1984)*

39. A high performance reading method for dosimetric TLmeasurements, A. Seethapathy, S. Kannan, V. Geetha and P.Gangadharan, Eleventh Annual Conference on RadiationProtection, Defence Laboratory, Jodhpur, (1984)•

40. Portable versatile digital dosimeter for beam outputmeasurements with *°Co units and accelerators, A. Sankaran,V.S.Patki and P. Gangadharan. AMPI Med. Phys. Bull. 10 (4)(1985) 206.

41. Derivation of absorbed dose in tissue equivalent phantomsusing the DRP secondary standard and digital dosemeters.A. Sankaran, AMPI Med. Phys. Bull. 11 (2) (1986) 81.

42. Compact rugged solid state film scanning densitometer systemfor radiation field analyser, A. Sankaran and A. Narayanan,AMPI, Med. Phys. Bull. 11 (3 & 4) (1986) 302.

43. Patient dose measurement and quality assurance tests in X-raydiagnosis with a novel 'Diamenter' and photo detector system,A. Sankaran, V.S. Patki and R.S. Gokarn, AMPI, Med. Phys.Bull 11 (3 & 4) (1986) 320.

44. A microprocessor controlled radiation survey meter, S.Kannan, M.D. Lalsare and P. Gangadharan, ThirteenthConference on Radiation Protection, VECC, Calcutta (1986).

45. Investigations on a scanner for radiation field studies, A.Sankaran Ph.D. Thesis, University of Bombay (1986).

46. DRP Secondary standard dosimeter - A field performanceevaluation, M.R. Deokar, P. Jacob and P. Gangadharan, AsianRegional Conference on Medical Physics, BARC, Bombay (1986).

47. Development of thermoluminescent personnel monitoring system,BARC Report 1336 (1986).

48. A microprocessor based film dosimeter reader, H. Mittal, R.N.Das Sarma, K. Aravindakshan and P. Gangadharan, AsianRegidonal Conference on Medical Physics, Bombay (1986) 298.

49. A versatile multiparametric dosimetry data acquisition systembased on 8085 processor, A. Sankaran, N.C. Pal and V.S.Patki, AMPI Med. Phys. Bull. (Abstract), Paper IV/2, 12(4) (1987).

: 142 :

50. A low power microprocessor controlled dosimeter, M.D.LaIsare, S. Kannan, M.R. Deokar and P. Garyadharan, Ibid(Abstract), Paper IV/3.

51. A compact TL reader for dose output measurements, H.K.Pendurkar, A.T. Soman, J.S. Nagpal and P. Gangadharan, Ibid-(Abstract), Paper V/17.

52. A heater controller with cold junction compensation forpersonnel monitoring TLD badge reader, R.N. Das Sarma,H.K. Pendurkar, A.K. Pathan and P. Gangadharan, Ibid.(Abstract), Paper V/18.

53. Scintillation monitor for monitoring radiation levels aroundcolour TV receivers, G. Ramanathan, V.H. Risbud andP. Gangadharan, Ibid. (Abstract), Paper V/19.

54. An improved semiautomatic TLD Reader, P. Ratna, S. Kannan andP. Gangadharan, Ibid. (Abstract), Paper V/20.

55. Quality assurance check of personnel monitoring systems,J.S. Nagpal, Geetha Varadharajan and P. Gangadharan,Ibid. (Abstract), Paper V/32.

56. A microprocessor based film dosimeter reader, H. Mittal,R.N. Das Sarma, K. Aravindakshan and P. Gangadharan, Proc.of the 3rd National Convention of Electronic andTelecommunication Engineers, Bombay, Dec. (1987).

t 143 t

E. MEDICAL JPHYSICS AND SURVEILLANCE CELL

P.S. Iyer

1. Service .Activities

1.1 Licensing and_ advisory activities

The Division authorises institutions for procurement ofradionuclides, both from India and abroad for medical andresearch purposes. This authorisation is based on factors suchas availability of adequate facilities, qualified staff andappropriate radiation detection equipment. The user institutionmust formulate its proposal for the radiation facility and senddetails of the same along with necessary drawings to thisDivision. The installation plans are evaluated for theirshielding adequacy, on an individual basis and modifications,wherever necessary are recommended. The types of installationsfor which advice is given include (i) beam therapy, (ii)brachytherapy, (iii) nuclear medicine, <iv) radioimmunoessay, (v)diagnostic X-ray, (vi) open isotope research laboratories and(vii) gamma irradiation plants.

1.2 Radiation surveillance

As part of the radiation surveillance programme in thecountry, the Division conducts radiation protection surveys ofdiagnostic X-ray, radiation therapy, nuclear medicine and openisotope facilities. The purpose of these surveys is on-the-spotevaluation of the radiation safety status including equipmentparameters and work practices. Pre-commissioning surveys ofradiation therapy and other high activity facilities are alsocarried out. The staff of the Division supervises the telegammasource replacements from the radiation safty view point andadvises the institutions in radiation emergencies. Radiationequipment are evaluated for type approval.

1. 3 Medical physics activities

The Division provides theoretical and experimental dosimetryservices to radiation therapy centres. These include (i) designand fabrication of wedge filters, manual after loadingapplicators and storage/transport containers, (ii) measurementsof dose distributions in beam and brachytherapy (iii) softwaredevelopment and its use for generation of complete dosedistribution for photon beams, electron beams and brachytherapy.In addition, dosimetry is worked out for non-conventional sourcearrangements on individual basis and also provided for 1-125 andIr-192 seeds/wires. Appropriate advice is given on specificmedical physics problems of the institutions.

I 144 J

1.4 Collection and disposal of radium

Because of the potential hazard associated with thecontinued use of radium sources in cancer treatment, a nationalprogramme has been initiated for the collection and disposal ofradium in a phased manner. Necessary technical advice andassistance is given by this Division for the radium sources to bepacked and sealed in appropriate containers and transported,generally by road to BARC for disposal.

1.5

A.

Summary of activities in 1986-1987

Installations approved1.2.3.

Beam TherapyBrachytherapyOpen Source

1987

81434

198

91235

Total 56

B. Authorisation to procure radionuclides

1. Medical2. Research

378558

Total 936

C. Radiation protection surveys

Total 95

56

289417

706

1.2.3.4.5.

Beam TherapyBrachytherapyNuclear MedicineRadioisotope Lab.Diagnostic X-ray

(Research)

275142029

308

153072

155

D. Telecobalt source replacement

B. Performance test-Telecobalt unit

17

5

15

5

: 145 :

2. Nuclear Medicine Advisory Services

2.1 Estimation of finger dose while handling Tc99* generators

K.S. Kini, Geetha S. and T.V. Venkateswaran

Tc-99m is routinely used for imaging purposes in NuclearMedicine Centres. In India, the Tc-99m is extracted by solventextraction method from the indegenous Mo-99: Tc-99m generatorsupplied by BARC. The extraction of Tc-99m involves a fewoperations in which large activities <50-500 mCi) are transferedfrom one container to another. This can lead to high exposure tofingers of the technicians if proper care is not taken. Tc-99mlabelled radiopharmaceuticals with 2-20 mCi of Tc-99m areinjected to patients, which can also give high exposure to thefingers of the person injecting. A technique has been developedto measure the exposure to fingers using LiF-Teflon discs (10 mmdia x 0.8 mm thick) mounted on plastic moulded ring*. Standardannealing procedures were followed for the dosimeters. A photoncounting unit designed and developed in the Division was used forreading the dosimeters.

42 radiation workers from 14 institutions have beenmonitored so far. The range of exposure to fingers received bythese workers is 0.1 - 1.0 mR/mCi of Tc-99m extracted (forextraction) and0-1-3.2 mR/mCi injected (for injection).

2.2 Finger dose monitoring of scintiqraphy workers

K.S. Kini and Geeta S.

Tc-99m labelled radiopharmaceuticals with activities rangingfrom 2 to 20 mCi are used for imaging purposes. The workershelping the patients at the imaging table can receiveconsiderable exposure to their hands/fingers, depending on theworkload, and the time they spend with the patients. TLD-ringdosimeters, developed by us for finger dose measurement ofworkers engaed in extraction and injection of Tc-99m, were usedfor measurement of finger doses of scintigraphy workers.Monitoring was carried out at 4 institutions in which 250procedures were carried out involving 7 radiation workers.Average activity/procedure was around 12 mCi. The exposurereceived per procedure ranged from 0.2 to 1 mR. which is wellwithin permissible limits.

: 146 i

2-3 Thyroid radioiodine-131 burden measurement

K.S. Kini and T.V. Venkateswaran

Radoiodine-131 is used for diagnostic and therapeuticpurposes of thyroid diseases. Handling millicurie levels of I-131 in the open form (liquid) can lead to internal contaminationin the radiation worker. A simple method of measuring theinternal contamination of 1-131 is to measure the radioactivityin the thyroid by external counting of 364 keV gamma rays emittedby 1-131 in the thyroid. Counting was done using the medicalspectrometers available at the respective institutions.Initially, the sensitivity of the spectrometer was determinedusing an 1-131 source whose activity was accurately measured atBARC. The source vial was placed in a standard neck phantom keptat the measuring distance from the detector. The 1-131 burden inthe thyroid was calculated from the thyroid counts obtained andthe sensitivity of the counting system. In all 64 workers from 15institutions in the country were monitored. 1-131 was detected in3 persons, with activities 70 nCi, 100 nCi and 370 nCirespectively. The presence of the activities in these workerswas attributed to bad work practice.

2.4 Monitoring of relatives of patients treated with 1-131

K.S. Kini, Geetha S. and T.V.Venkateswaran

Thyrotoxic or Ca-Thyroid patients, treated with 1-131, willbe having a few millicuries of 1-131 in their body,after theirdischarge. The gamma radiation from 1-131 in the patient canirradiate the people staying with patient, the exposure dependingon the proximity and time, the relatives spend with the patient.A technique has been developed to measure this exposure torelatives, using TL dosimeters. 5 mm dia x 0.8 mm thick CaSO«:Dydiscs ( 6 nos) are loaded in nylon lockets, specially made forthe purpose in the Division. The TLD lockets are worn by therelatives for 2 weeks from the time the patient arrives at homeafter administration of the radioactivity. The dosimeters areread in a photon counting unit, designed and developed in theDivision. Calibration of the dosimeters is done using a Rente a 1human phantom on which the TLD loaded lockets are worn and astandard neck phantom containing accurately measured 1-131activity.

Nine relatives of two thyrotoxic patients administered with3.2 and 5.7 mCi of 1-131 were monitored for two weeks. Themaximum exposures received by the relatives in the two-cases were17 mR and 26 mR respectively in a period of two weeks.

: 147 :

2.5 Monitoring of personnel handling 1-125 inradioimmunoassay laboratories

P.K. Gaur and T.V. Venkateswaran

As some of the RIA research centres 1-125 is used foriodination work. In this process sometimes users inhale theradionuclide andreceive thyroid burden. Such users are monitoredfor thyroid activity with a thin Nal (T| ) detector and using Sum-Peak method suggested by F.L. Bordell. Sixty two persons weremonitored out of which 46 were found to have 1-125 activity inthyroid. The values ranged from 37 Bq to 2.2 KBq. Assuming 42days effective half-life the intake was calculated which wasfound to be from 86 Bq to 4.2 KBq. The committed dose equivalentranged from 5.1 to 9.5 mSv.

2.6 Monitoring of personnel during special procedures

Geetha S. and S.J.Supe

In diagnostic radiology most radiation exposure is receivedduring special procedures as the medical personnel are to bepresent during flouroscopy unlike radiography. In most of theradiology depts, medical and paramedical staff wear lead apronscovering part of their body. Commonly only one personneldosimeter is worn by them. Also ICRP-26 has recommended theweighting factors for tissues at risk and has defined EffectiveDose Equivalent (EDE). The evaluation of EDE from the dosemeasured at this single position then becomes difficult. In anattempt to evaluate EDE we have monitored the personnelconducting special procedures at 13 body locations representingvarious critical tissues. Thermoluminescent dosimeters incapillary form were used for monitoring the surface dose. Forthe calculation of organ dose the surface dose was multiplied bythe corresponding percentage depth dose factor. The organ doseswere then multiplied by the corresponding weighting factor foreach of the tissues at risk. The EDE was computed by summing upthe weighted doses. The results are presented in table. 1.

: 148 :

Table 1. CHEST DOSES, IC1P PE1SOI DOSES AID COIVUSIOI F1CTOES FOK VARIOUS SFECIIL PROCEDURES.

Dote

Chest dose is1ST

ICIP persondose in iSv

Coorersioofietorsfor ICIPptrton dote

Evaluatedannual eyeleoi dotein IST

ETtluttedanual ICIPptrtoa dotein IST

Pertonnel

RadiologistStaff nurseTechnicians

RadiologistStaff nurseTechnicians

RadiologistStiff nariiTechnicians

RadiologistStaff airteTechnicians

RadiologistStaff nurseTecksicim

Vertebralaogiograi

C.0110.0130.012

0.00140.00970.0076

0.760.710.63

1.1011.101.34

1.611.941.50

Carotidanyiogrn

0.0050.009

0.00460.0024

1.020.72

4.50t.Ol

1.410.72

Selectiveangiograi

0.020.009

O.Olt0.0051

O.JJ0.63

15.004.72

1.770.62

Cardiaccatheteri-tttioi

0.0250.0050.013

0.0160.00530.0065

0.641.110.50

10.206.457.10

2.450.751.72

Uytlojrai

0.006

0.0065

1.11

19.20

1.92

Bariai aeal

0.003

0.0021

0.7J

9.00

3.30

2.7 Nuclear medicine centres in India

Geetha Sadagopan and T.V. Venkateswaran

Table 2. Data on nuclear medicine centres.

Number of nuclear medicine centres

Number of centres with Mo-99generator

Number of centres having gamma camera

Number of clinicians authorised

Number of centres using 1-131for cancer therapy

87

35

27

98

12

: 149 t

PUBLICATIONS

1. Mould therapy using cathetron source pencils, A. Shanta,Strahlentherapie, 158 (1982) 34.

2. SI units-use of air kerma for the replacement of exposureandassociated quantities in radiological dosimetry, P.S.Iyer, Strahlentherapie, 158 (1982) 365.

3. Monte Carlo calculations of the dose distribution across aplane bone marrow interface during diagnostic x-rayexaminations, R.N. Kulkarni,Brit. J. Radiol. 54 (1982) 875.

4. Dose rate tables for Cobalt-60 medical tubes and needles,A. Shanta and U.B. Tripathi, AMPI Med. Phys. Bull. 7 (1982)178.

5. Analysis of radiation exposure to personnel working innuclear medicine centres in India, T.V.Venkateswaran andGeetha S., 5th annual conference of AMPI, Coimbatore(1982) .

6. Quality assurance test for diagnostic X-ray machines,P.Ayappan, P.S. Viswanathan, A.K. Gopalakrishnan, H.A.Sabuwala and K.R. Das, AMPI Bull. 8 (1983) 38.

7. Evaluation of indigenous X-ray intensifying screens, P.Ayappan and P.S. Iyer, AMPI Med. Phys. Bull. 8 (1983) 17.

8. Importance of acceptance tests in clinical dosimetry andtreatment planning, P.S. Iyer, Ind. J. of Radiol. 37 (2)(1983) 185.

9. Experiences in implementing radiation safety inradioluminous paint workshop handling tritium, P.K. Gaurand T.V. Venkateswaran. Xth annual conference of IARP.Bombay. (1983).

10. Measurement of Iodine-125 burden in workers from RIALaboratories, P.K. Gaur and T.V. Venkateswaran, 6thConference of AMPI, Srinagar (1983).

11. Calibration and intercomparison of medical spectrometers atvarious Nuclear medicine centres and measurements ofthyroid radioiodine-131 burden in radiation workers, K.S.Kini, T.V. Venkateswaran and P.K. Gaur, VI annualconference of AMPI, Srinagar (1983).

12. Present status of radiation protection in nuclear medicinecentres in India, T.V. Venkateswaran, XVth annualconference of Society of Nuclear Medicine, Jaipur (1983).

13. Monitoring of radiatison workers in nuclear medicinedepartments handling 1-131, K.S. Kini and T.V.Venkateswaran, Bull. Rad. Prot. 6 (1983) 23.

14. Energy absorption and attenuation coefficient values forbrachytherapy nuclides, A. Shanta and U.B. Tripathi, AMPIMed. Phys. Bull. 9 (1984) 159.

15. A sim^xe formulation for the dosage in mould andinterstitial therapy, (Abstract), U.B. Tripathi and A.Shanta, AMPI Conference, Calcutta, (1984).

: 150 t

16. Interstitial therapy of breast cancers using Iridium-192wires, (Abstract), K.R. Das, R.N. Kulkarni, A. Shanta, A.M.Pendse and R. Pandhi, AMPI Conference, Calcutta (1984).

17. A simple computational approach to irregular fielddosimetry, N.Y.Kelkar and U.B. Tripathi, Strahlentherapie(1984).

18. A general formulae for the computation of tissue air ratiovalues of radionuclides commonly used in brachytherapy,U.B. Tripathi and A. Shanta, Med. Phys. 12 (1985) 88.

19. Radium substitutes comparison of physical parameter andadvantages, P.S. Iyer and A. Shanta, Proc. Workshop onradium substitutes and brachytherapy techniques, BARC andTMH, Bombay (19*5) 23.

20. Exposure to finvars while handling a solvent extractiontype Technetium-99m Generator, K.5. Kini and T.V.Venkateawaran, The J. Nucl. Med. 26 (1985) 650.

21. Radiological protection aspects of radioiodine therapy forcancer of the thyroid, S.D. Soman and T.V. Venkateswaran.,National Seminar on Thyoid cancer : role of radionuclidesin its diagnosis, management and treatment, Bombay (1985).

22. Radiography and dosimetry of template implants, P.S. Iyerand A. Shanta, Technology transfer programme inBrachytherapy, Proceedings TMH, Bombay (1986) 125

23. Dosimetric aspects of breast and soft tissue sarcomaimplants, K.R. Das, A. Shanta, R.N. Kulkarni, R. Pandhi,B.N. Vithal and S.M. Deore, Techdnology transfer programmein Brachytherapy proceedings, TMH, Bombay (1986) 153.

24. Estimation of radiation dose from Iridium-192 wire handlingin brachytherapy, A.Shanta, S.M. Deore, S. Ramaswamy andK.R. Das, AMPI Med. Phys. Bull. Proc. of Asian RegionalConference, Bombay 11 (1986) 523.

25. Current ICRP specification for protection against ionizingradiation from external sources used in Medicine, P.S.Iyer, AMPI Med. Phys. Bull.11 (1986) 11.

26. A general formulation for depth dose computation in photonbeam dosimetry (Abstract), U.B. Tripathi, AMPI Med.Phys.Bull. Proceedings of Asian Regional Conference Bombay11,(1986) 12.

27. An analytical equation for brachytherapy dosimetriccalculation (Abstract), U.B. Tripathi, AMPI Med. Phys. BullProc. of Asian Regional Conference Bombay, 11, (1986) 167.

28. Dosimetry of Iridium-192 line sources (Abstract), A.Shanta, U.B.Tripathi and K.R. Das, AMPI Med. Phys.Bull.Proceedings of Asian Regional Conference, Bombay 11 (1986)217.

29. Importance of reducing medical exposure, P.S. Iyer, Ind. J.Radiol. 40, 2 (1986) 161.

30. Involvement of medical physics in radiation oncology, P.S.Iyer, Ind.J. Rad. Oncology, 1 (1986) 13.

: 151 :

31. Radiation dose to extremities of technologist duringscintigraphy Procedures using Tc-99m. K.S. Kini, Geetha S.and T.V. Venkateswaran, XVIII annual conference of Societyof Nuclear Medicine, Bangalore (1986).

32. Ralstron 20 B, A high dose rate remote controlled afterloader for brachytherapy, K.R. Das, A. Shanta, R.N.Kulkarni and P.K. Shah, Endocrine therapy, HyperthermiaOncology, 3 (1987) 81.

33. Effect of the geometry of vaginal sources in the treatmentof carcinoma of cervix uteri, K.R. Das. A Shanta, R.N.Kulkarni, and A.M. Pendse, AMPI Med. Phys. Bull. 12 (1987)23.

34. Treatment planning software for IBM compatible P.C., U.B.Tripathy, International Symposium on Dosimetry inRadiotherapy IAEA/WHO (1987).

35. Effort towards replacement of Radium by substitutes inIndia, P.S. Iyer and S.D. Sornan, Proc. of IXth Meeting ofInternational Working party for cancer of cervix, Adam &Hilger, 56 (1987).

36. Radiation and women, Geetha S. and T.V. Venkatewsaran,Presented at XIX annual conference of Society of NuclearMedicine, Hyderabad (1987).

! 152 :

F. INDUSTRIAL ADVISORY & CONTROL SECTION

G. Venkataraman

enders?

1 .1. Currently there are 416 isotope radiography institutionsand 304 nucleonic gauge users in the country. At present thetotal number of gamma exposure devices (projectors/cameras)stand at 754 (Ir192) and 31 (Co-60) whereas the number ofnucleonic control systems in use are 1128. There is a growthrate of 41% and 90% in gamma radiography users and nucleonicgauge users respectively over the 5 year period under review.

Table 1. The work carried out on an average every year as of1986.

a. Industrial radiographic site inspections

b. Cameras inspected for their functionalperformance and leakage radiation levels

c. Authorisations issued for gamma radiographysources

d. Designs of buildings for housing radiologyfacilities scrutinised and approved

e. Advice on radiation safety andallied aspects

f. No objection certificates issued for importof radioactive materials

350

350-400

900-950

35-40

1800

250

1.2 Assistance was sought in the case of 27 unusual occurrencespertaining to industrial gamma radiography equipment/workpractices. This comprises of 14 Ir-192 radiographyequipment/work and the remaining of Co-60/Cs-137 equipment.Further, 7 incidents involving unusual occurrences withnucleonic gauge sources were handled. Remedial measures toprevent recurrence of such incidents were identified andenforced.

1.3. The group has developed designs of three lead collimatorsfor use in pipe line inspection, for work with Iridium-192sources. These are available for intending users on demand.

: 153 :

1.4. Apart from plans of buildings designed to house X-raymachines or isotope radiography equipments, the group hasscrutinised the following special type of drawings and offeredappropriate guidance to achieve built-in safety coupled witheconomy.

a) 6-10 MV accelerator facility in NDT Departments atBombay, Poona, Sriharikota and Trivandrum.

b) 25000 curie Co-60 irradiation facility for research andindustrial treatment at Shriram Inst. Ind. Res., Delhi.

c) Building to house Kilocurie Co-60 sludge hygienisationirradiation facility. Municipal Corporation of Baroda,Baroda.

1.5 The group supervised prototype tests on nucleonic gaugesystems indigenously developed by two private Bombay basedagencies to assess the claimed design safety of such devices.

2. Internal monitoring of workers handling radioluminous paint

P.K. Gaur, Smt. Geetha Sadagopan and T.V. Venkateswaran

There are about twenty centres in the country where largequantity of radioluminous paint is used in open form. Theworkers engaged in this work are monitored routinely forinternal burden and annual dose estimation. The luminous paintis either activated with Pm-147 or H-3. The specific activityof the paint is high and varies from 700 GBq to 20 TBq per kg ofpowder.

2.1 Measurement of Pm-147 burden

Pm-147 burden is estimated by carrying out bioassay andcounting liver activity with whole body counter coupled withphoswich detector. The bremsstrahlung coming out of the organare detected to count liver activity. The whole body counter iscalibrated in the energy band 12-75 keV using Remcal phantom andMDA (minimum detectable activity) is calculated. It is found tobe 0.9 KBq. The bremsstrahlung spectrum detected from a workerwho has 26.6 KBq of Pm-147 in liver is shown in Fig. 1. About 30workers were monitored and three were found to have liver burdenof 10.7, 26.6 and 27.6 KBq.

2.2 Measurement of H-3 burden

In case of H-3 users, the internal contamination isestimated by urine analysis. The urine samples are collectedfortnightly and analysed. Each time the probable intake andabsorbed dose are calculated from the data supplied by theinstitution regarding their work period. The biological half

t 154 :

I

120

100

to

«0

40

10

(a) COUNTINO TIMK tOOmtoi(b) COUNTINO TIMK 40 Mln

t.

* . . •

4 . « 1 « t . •* I . I . > . I . I • _ L j I i

0 20 30 40 10 f 0 70 10 M 100 HO fc«V

ENERGY

Fig.l (a) External bremestrflhlung detected from l iver ofa worker having Pm-147 burden

(b) Background distribution in the steel room.

1

n» urn v* M M oci MC

M0MTM>

Pig. 2 Estimation of H-3 intake in a radiation worker.

: 155 :

life for H-3 in these workers is calculated and found to be 7days. An example of systematic calculation of intake is givenin Fig. 2. The total intake is obtained by adding intakes in ayear and is compared with Annual limit of Intake (ALI) given byICRP-30. The annual dose of each worker is also calculated fromthese curves. The annual dose, received during 1982-86 by theworkers of an industry handling 37 TBq of H-3 in a year, isgiven in Table 2. In addition to this periodic air monitoringis done to keep the air contamination level below the DerivedAir Concentration (DAC) limits.

Table 2. Annual dose of the radiation workers handling H-3activated paint.

Workers

IIIIIIIVV

VIVII

VIIIIXX

XIXII

XIIIXIV

1982

12.24.06.911.913.313.8-------—

Annual

1983

2.482.822.625.353.781.690.0460.4060.267----—

Dose in mSv

1984

0.180.87-1.670.311.150.090.300.441.191.61--—

1985

1.041.280.72-2.182.240.762.081.161.220.900.59-—

1986

3.843.87----0.220.720.070.490.600.231.720.47

Publications

1 A method for the determination of depth of a point sourceof beta emitter from bremsstrahlung measurements. P.K. Gaurand T.V. Venkateswaran, Nucl. Inst. and Meth. 204, (1982)213.

2. Revision of A Bomb iosimetry - A report, G. Venkataraman,Bull. Radiat. Prot. 5 (1982) 59.

3. Medical supervision of radiation workersA.N. Nandakumar and G. Subrahmanian, Bull.(1982) 61.

4. Evolution of radiation risk estimatesradiation protection practice (Abstract).AMPI Med. Phys. Bull. 7 (1982) 12.

5. Practical implications of New ICRP concepts in monitoring.G.Venkataraman, Bull. Radiat. Prot. 6 (1983) 33.

S.B.Radiat.

Santani,Prot. 5

: Implication inP. Subrahmanyam,

: 156 t

6. Radiation incidents in industrial radiography, G.Subrahmanian and V.G.R. Subramanian, DAE workshop on RecentAdvances in Industrial Radiography, Bombay, Jan. (1983).

7. Influence of repair on the shape of survival curves ofgamma irradiated yeast, (Abstract), P. Subrahmanyam andN.M.S. Reddy, AMPI Med. Phys. Bull. 8 (1983) 50.

8. Radiological safety status in defence establishments inIndia,(Abstract) Vijaya Krishnan, V.G.R. Subramanian, B.Nagalakshmi, R. Sadagopan and G. Subrahmanian,11th Annual Conf. IARP. Jodhpur, Feb. (1984).

9. Law and regulations. G. Venkataraman Bull. Radiat Prot. 7(1984) 61.

10. Certain problems in open-top radiography installations, P.Subrahmanyam and G. Subrahmanian, Inter. Conf. Applicationof Radioisotopes and Radiat. in Industrial Develop. Bombay,March (1984) .

11. Monitoring of radiation workers handling radioluminouspaintSi P.K. Oaur and T.V. Venkateswaran, Proceedings of6th International Congress of International RadiationProtection Association on -Radiation-Risk-Protection Berlin(1984).

12. Evaluation of effective dose equivalent from diagnosticspecial procedures, Geetha Sadagopan and S.J. Supe, Bull.Radiat. Prot. 7 (2-3) (1984).

13. Radiation dose to patients during radionuclide and X-raydiagnostic investigations, Geetha Sadagopan and T.V.Venkateswaran, AMPI Med. Phys. Bull. 10 (3) (1985).

14. Brief account of some radiation incidents in industrialradiography sites, G. Subrahmanian, R. Kannan and V.G.R.Subramanian, NAARRI News 7 (1985) 5.

15. Minimising radiation hazards while using indigenous iridiumradiography cameras for pipe line inspection work atproject sites, P. Subrahmanyam, M.S. Sundaram and V.G.R.Subramanian, Bull. Radiat. Prot. 9 (1986) 21.

16. Theoretical calculation for thermal test for a Type B.package containing 10,000 Ci of Cobalt-teletherapy source.(Abstract), A. Sharma, AMPI Med. Phys. Bull. 11 (1986) 527.

17. Probability of causation, G. Venkataraman, Bull. Radiat.Prot. 9 (1986) 71.

18. Guidelines for the RSO to implement radiation protectionrules in industrial radiography. D. Singh and P. Subrahma-nyam, AERB/RSD/Gen-1 (1986).

19. These need not have happened : News digest on incidentsinvolving sealed radioisotopes reported by USNRC, G.Venkataraman, NAARRI News 8 (1986) 10.

20. Radiation safety in radioluminous paint workshop handlingtritium activated paint, P.K. Gaur and T.V. Venkateswaran,Bull. fcadiat. Prot. 9 (1986) 13.

t 157 *

G. TRANSPORT ADVISORY SERVICES

J.S. Bisht, A.N. Nandakumar, K.C. Upadhyay and M.G. Bhide

1. The responsibilities of the group are as follows:

(a) The group tenders advice regarding safe transport ofradioactive materials including fissile materials in specificinstances of transport on day to day basis.

(b) The group is engaged in carrying out assessment of packagedesign and recommending them to AERB for approval of packgesdesigned in India and for validation of design approval forpackages of foreign design.

(c) The group issues transport certificates for routineshipments of radioactive material in Type A and excepted packagesincluding safe guard samples for IAEA, Vienna and also Type Bpackages containing teletherapdy sources, gamma chambers and highactivity irraditors.

(d) Type B packages are checked for radiation levels, labellingmarking and tiedown, prior to departure from BARC.

(e) For enabling the Director General of Civil Aviation to issuepermission to the concerned airlines for airfreightingradioactive materials into India, from any country the necessaryclearance certificate is issued by this group on the basis of thedetails regarding the consignments.

(f) Port clearance advice is issusd by this group to enableconsignees in India to clear radioactive consignments brought toIndia by ships.

(g) Advice is tendered to users regarding transportation ofradioactive waste to BARC for disposal in coordination with theIsotope Division/Waste Management Division, BARC.

(h) The group handles abnormal situations involving radioactiveconsignments such as accident during transport, loss of packagesand non-delivery of packages at the destination.

(i) Members of the group participate in activities related tosafety in the transport of spent fuel and provide an escort foreach shipment from RAPS, KOTA to PREFRE, Tarapur or NAPS,Kalpakkam to PREFRE, Tarapur.

2. The group prepared radiation protection guides on specifictopics related to transport of radioactive material. The groupwas entrusted with the task of bringing out similar guides on

: 158 t

other topics related to radiological safety in collaboration withthe concerned members of DRP.

3. Members of the group participated in the deliberations ofIAEA Advisory Groups and Technical Committee meetings relating toTransport of Radioactive Materials.

4. Members of the group contributed to the preparation of IAEAsafety series No.6,7,37,80 and 87 all relating to safe transportof radioactive materials.

5. Members of the group participated in an IAEA ResearchContract on Methods of Assessmentof radiation dose to transportworkers and members of the public due to transport of radioactivematerials.

6. The group had extensive dialogue with the Indian Railways ontransport of radioactive materials and prepared a draft chapteron radioactive material for inclusion in Railway Red Tariff.

7. The group has prepared a detailed emergency response planfor transport of radioactive material.

PUBLICATIONS

1. An examination of some of the aspects of the IAEAregulations for safe transport of radioactive materials,A.N. Nandakumar and D. Singh, Bull. Rad. Prot. 5(2) (1982).

2. Seminar on safe transport of radioactive materials-organizedby Division of Radiological Protection, Feb. 1984.

3. Proposed changes in IAEA regulations for the safe transportof radioactive materials and their implication: J.S. Bisht,K.C. Upadhyay and G. Subrahmanian, XI Annual Conference ofIARP, Defence Laboratory, Jodhpur, (1984).

4. Radiation protection guides for the benefit of radiationworkers and general public , D. Singh, A.N. Nandakumar, J.S.Bisht, Amiya Sharma, K.C. Upadhyav and G. Subrahmanian-Bull. Rad. Prot. 7 (1) 1984).

5. Assessment of radiation dose received by transport workersresulting from radioactive shipments-development of a modelfor airport workers, K.G. Vohra, A.N. Nandakumar, R.K. Kherand S. Ramakrishna Iyer, Rad. Prot. Dos. 9(4) (1984) 283.

6. A method of assessment of annual collective dose received bythe public due to urban transport of radioactive materials,K.G. Vohra, G. Subrahmanian, A.N Nandakumar, R.K. Kher andS. Ramakrishna Iyer Rad. Prot. Dos. 9 (4) (1984) 287.

: 159 x

7. Through an apparent maze of transport regulations, A.N.Nandakumar, J.S. Bisht and G. Subrahmanian. XII AnnualConference of IARP March (1985).

8. Advisory services in safe transport of radioactive materials,K.C. Upadhyaya, A.N. Nanddakumar, J.S. Bisht and G.

Subrahmanian; XV Conference on Radiation Protection, March(1988) .

9. Control of contamination due to spent fuel storage poolwater by electric method, P.B. Choudhari and M.G. Bhide, XIIAnnual Conference on IARP, Bombay March, (1985).

10. Design of a faraday cup monitor for 8 MeV linear acceleratorK.S. Sharada and M.G. Bhide, Bull. Rad. Prot. 10(4)(1987).

11. Predominance of positive ions in the activity of spent-fuelstorage pool water, M.G. Bhide, Health Phjfc. 46,(6) June(1984) 1301.

12. Experience in regulating the transport of radioactivematerials in India, A.N. Nandakumar, J.S. Bisht, G.Subrahmanian, Proceedings of International Symposium on thePackaging and Transportation of Radioactive Materials(PATRAM1 86) 1, IAEA, Vienna, 1987.

13. Transport of radioactive materials in the nuclear fuelcycle, J.S. Bisht, A.N. Nandakumar, K.C. Upadhyaya and G.Subrahmanian, Bull. Rad. Prot.9(3) (1986) 17.

14. Regulations for the safe transport of radioactive materials,K.G. Vohra, G. Subrahmanian, J.S. Bisht and A.N. Nandakumar,Safety Series No. 6; (1985).

15. Advisory material for the IAEA regulations for the safetransport of radioactive material, G. Subrahmanian and A.N.Nandakumar. Safety Series No. 37 (1985) Third Edition.

16. Explanatory material for the IAEA regulations for the safetransport of radioactive material, G. Subrahmanian and A.N.Nandakumar, Safety Series No.7 (1985 Edition) Second Edition

17. Discussion of and guidance on the optimization of radiationprotection in the transport of radioactive material, J.S.Bisht, IAEA-TECDOC-374 IAEA, Vienna 1986.

18. International studies on certain aspects of the safetransport of radioactive materials (1980-1985), IAEA-TECDOC-375 (1986) .

19. Schedules of requirements for the transport of specifiedtypes of radioactive materiald consignments, A.N. NandakumarSafety Series No. 80 IAEA Vienna, 1986.

t 160 t

20,

21

22

23.

24.

25.26.

27,

28.29.

30.

31.

Emergency response planning and preparedness for transportaccidents involving radioactive materials, A.N. Nandakumar,Safety Series No. 87 IAEA Vienna, (1988).Maximum permissible activities in radioactive consignments.RPG/TR-1, (1982).Requirements for safe transport of exempt pakaces RPG/TR-2,(1982).Safety in handling and storage of radioactive consignmentsRPG/TR-3, (1982).Emergency response planning for transport accidentsinvolving radioactive material RPG/TR-4, (1982).Safe transport of tritiated water RPG/TR-5, (1982).Safe transport of low specific activity materials RPG/TR-6,(1982) .Requirements for safe transport of irradiated nuclear fuelRPG/TR-7, (1982).Safe Transport 06 Fissile Materials RPG/TR-9, (1963).Requirements for labelling and marking ofconsignments RPG/TR-8, (1982).Radiological safety in the manufacture ofincorporating thorium nitrate RPG/IND-1, (1982)Radiation protection considerations in theoperation aspects of medical electroninstallation RPG/M-2, (1983).

radioactive

gas mantles

design andaccelerator

: 161 :

H. EDUCATION AMD TRAINING

The Division has conducted or taken part in several courseson radiation safety, applications and related subjects duringthis period; as given in Table 1. Many of these programs wereorganised and conducted by this Division in Trombay. The coursesin industrial radiography were held in cosponsorship witiiorganisations such as NAARRI (National Association forApplication of Radioisotopes and Radiation), BHEL(Tiruchirapalli, Hyderabad), MERADO (Pune), Mazagoan Docks(Bombay), I.I.T. (Bombay and others) and conducted in Bombay orvarious outstations. Courses in nucleonic gauging and loggingwere held at the request of various organisations like ONGC attheir sites and for their staff.

The staff of the Division have taken lectures for the thefollowing courses of the Bombay University:

1. M.Sc. (Biophysics)2. DMRD (Radiodiagnosis)3. DMRT (Radiotherapy) and MD (Radiotherapy)

Students from other institutions have received practicaltraining in this Division on safety related subjects. This is ofabout 5 to 10 days duration.They are:

1. M.Sc. (Medical Physics), Anna University, Madras2. Diploma in Radiation Medicine, University of Delhi, Delhi3. X-ray Radiographers' Course, Medical College, Trivandrum

This Division has taken part in a few courses conducted byother organisations, e.g.

1. Workshop in Occupation Medicine - conducted by AERB in1987 ( 4 lectures)

2. Techniques of Radioimmunoassay conducted by Isotope Group(4 lectures in each course).

3. Course on Accident Prevention in Industry - conducted byHealth Physics Division ( 2 lectures).

4. Civil Defence & Emergency Preparedness - organised byIndian Navy (10 lectures).

An educational and scientific exhibition was held in March1984 on "safety with radiation' at the Nehru Science Centre,Bombay. Panels as well as equipment/instruments related toradiation safety and hazards were displayed for appreciation «indacquaintance of public.

Radiation protection in diagnostic radiology was adopted as

: 162 t

theme at 4 workshops held under the aegis of Indian Associationfor Radiation Protection held at Agra (1982), Trivandrun (1983),Bangalore (1984) and Lucknow (1986). At the Lucknow workshop,posters and panels in the exhibition were presented in Hindi.

Specific requests for training of persons in the Divisionhave always been complied with. Every year students from localcolleges/polytechnics spend time in the Division learning aboutradiation measurement and associated electronics. One visitoreach from Indian Navy and Syria was given exposure to all theactivities in the Division.

Table 1. Education activities of Division of RadiologicalProtection.

S.No.

1.

2.

3.

4.

5.

6.

7.

8.

Name of the course

Dip.R.P. / BombayUniversity. Postgraduate diplomain radiologicalphysicsSafety in medicalradiologySafety in researchapplications ofionising radiationSafety in the useof radioactiveluminous compoundsIRG-1 course forsite-in-charge inindustrialradiographyIndustrial radio-graphers' certifi-cation courseSafety in nucleonicgauges and loggingsystemsSafety in servicingradiotherapyequipment

Duration

1 year

4 weeks

3 weeks

2 weeks

5 weeks

10 days

10 days

8 days

No. ofcoursesheld

6

2*

6

3

18

23

18

1

Approx.No. ofpersonstrained

100

50

150

25

500

600

500

12

* Discontinued since 1984

: 163 :

I. PUBLICATIONS 1988

1. Dose 'Assurance programme for high dose radiation facilitiesusing free radical dosimetry {spectrophotometric readout),R.M.Bhat, G.R.Narayan, S.R.Nilekani and B.L. Gupta, NationalConf. on Industrial Applications of Isotopes and RadiationTechnology, BARC, Bombay, (1988) .

2. A simplified procedure for dosimetry of radiation processingplants using glutamine free radical dosimeter, S.R. Nilekaniand B.L. Gupta, National Conf on Industrial Applications °fIsotopes and Radiation Technology, BARC., Bombay (1988).

3. Use of glutamine dosimeter for electron beams used inradiation curing, B.L.Gupta and S.R.Nilekani, Proc. of Conf.on Radiation Curing Asia, Tokyo, Japan, (1988) 391.

4. Radiation dosimetry in industrial irradiators, B.L. Gupta,UNDP/IAEA/RCA Regional Training Course on IndustrialRadiation Sterilization Quality Control and Compatibility ofMaterials, BARC, (1988).

5. CR-39 response measurements to neutrons in the energy range0.45 to 14.7 MeV, D. Sharma, M.G. Shahani and U.V.Phadnis,XVth IARP Conference, Hyderabad, (1988).

6. Photoelectric cross section for 6-20 keV photons inberyllium, carbon, magnesium, aluminium, silicon, jopper andlead, R. Nathuram, I.S.Sundara Rao and M.K.Mehta, Phys. Rev.A 37 (12) (1988) 4978.

7. Mass attenuation coefficients for beta particles in 4ngeometry, R. Nathuram, G. Subrahmanian and S.R. Thontadarya,Physica, C-151, . (1988) 547.

8. Calibration of iridium-192 wire sources, A. Shanta, P.N.H.R.Vijayam and U.C. Mishra, AMPI Med. Phys. Bull. 13, (1)(1988) 29.

9. TL emission spectra of glow peaks of CaF2:Tm, A.S. Pradhanand R.C. Bhatt, Radiat. Prot. Dosim. 20, (1987) 237.

10. Fast neutron response of sensitised LiF TLD-700, A.S.Pradhan, Int. J. Appl. Instr. Nucl. Tracks Radiat. Meas. 13,(1987) 111.

11. Highlights of the seventh national symp. on radiationphysics, A.S. Pradhan and A.N. Nakra, Bull. Radiat. Prot.10, (1987). 87.

12. Effect of doping with monovalent cation impurities on thethermoluminescence response of CaSO-i : Dy phosphor, BhuwanChandra, S.S. Shinde, A.R. Lakshmanan and R.C. Bhatt, Phys.Stat. Sol. (a) 103 (1987) 599.

13. Radiation damage in LiF (Mg,Ti) and CaSd.-Dy TLD phosphors,Bhuwan Chandra, A.R. Lakshmanan, S.S. Shinde and R.C. Bhatt,Bull, of Radiat. Prot. 10, (1987) 173.

14. Activation energy distribution of LiF(Mg,Cu,P) TL phosphor,J.K. Srivastava and S.J. Supe, 7th National Symposium onRadiation Physics, Mangalore university (1987).

15. High-lights of the ninth conference on medical physics(AMPI), Trivandrum, A.S. Pradhan, Med. Phys. Bull. 13,(1988) 67.

: 164 :

16. Seventh symposium on radiation physics, A.S. Pradhan andA.M. Nakra, Phys. News, 19, (1988) 116.

17. Laser heating as potential replacement for the conventionalheating of TLDs - A comment,Bhuwan Chandra, A.R. Lakshmanan,S.S. Shinde and R.C. Bhatt, Radiat. Prot. Dos. 18, (1987)114.

18. Role of non-radiative transmission processes and mechanism oflinear and non-linear-thermoluminescence effects, J.K.Srivastava, International Conference and Intensive TutorialCourse on Semiconductor Material, organized by IEEE,University of Delhi and Semiconductor Society of India, NewDelhi (1988) .

19. The thermoluminescence characterisation of LiF (Mg, Cu,P)phosphor, J.K. Srivastava and S.J. Supe, J. Phys. DrAppl.Physics, 21, (1988) 643.

20. Trap distribution analysis of LizB<O:Cu, thermoluminescencephosphor, J.K. Srivastava and S.J. Supe, second nationalSymposium on Defects in Insulating Solids, Paper No. B-16,Indian institute of Technology, Madras (1988).

21. On mechanism of linear and non linear thermoluminescenceeffects, J.K. Srivastava and S.J. Supe, Second NationalSymposium on Defects in Insulating Solids, Paper No. B-15,Indian Institute of Technology, Madras, (1988).

22. Phototransfer thermoluminescence in CaSO< :Dy - grain sizedependence, S.S. Shinde, A.R. Lakshmanan, B.C. Bhatt andR.C. Bhatt, Nucl. Instrum, and Meth. B.-31, (1988) 592.

23. The glow curve shapes of some thermoluminescence materialsfor alpha and gamma radiations, A.R. Lakshmanan, BhuwanChandra and R.C. Bhatt, Int. J. Radiat. Appl. Instrum. partA 39 (3) (1988) 203.

24. Grain size and Dy concentration effects in thermoluminescentCaSO* :Dy, A.R. Lakshmanan, S.S. Shinde, R.C. Bhatt and S.J.Supe, Rad. Prot. Dosim. 22 (3) (1988) 173.

25. Comments on "Removal of sodium from TLD CaSCNiDy", A.R.Lakshmanan, Rad. Prot. Dosim. 22 (3) (1988) 203.

26. Role of F-centres on the thermoluminescence process in pureand doped lithium fluoride crystals, A.R. Lakshmanan, BhuwanChandra and R.C. Bhatt, Cryst. Lattice Defects AmorsphousMater. 17(4) (1988) 431.

27. Simultaneous determination of dose and elapsed time afterradiation exposure using CaSCMiNa, Dy, A.R. Lakshmanan, B.C.Bhatt and R.C. Bhatt, 15th IARP Conference on RadiationRrotection, Hyderabad, Abstr. No. IARP/15/22(0) (1988).

28. TLD personnel monitoring service, R.K. Kher, S.K. Gupta,D.R. Singh and S.J. Supe, Ibid, Abstr. No. IARP/15/89(S).

29. Study of LiF doped with different cations for dosimetricapplications, K.L. Popli, R.K. Kher, M.S.K. Khokhar and S.J.Supe, Ibid. Abstr. No. IARP/15/32(0).

30. Development of AlzO3 - Teflon discs for dosimetricapplications, R.K. Kher, K.L. Popli, H.R. Sethumadhavacharand S.K. Mehta, Ibid. Abstr. No. IARP/15/32(0).

: 165 :

31. Application of PC for country wide personnel monitoringservice, A.V. Dere, N.V. Raman, B.D. Phadke and R.K. Kher,Ibid, Abstr. No. IARP/15/30(P).

32. A novel X-ray transmission ionization chamber dosimeter forpatient dose measurements in diagnostic radiology, A.Sankaran and V.S. Patki, Brit. J. Radiol. 61, (1988) 613.

33. A semiautomatic film badge dosimeter reader, H. Mittal, UmaGaonkar and P. Gangadharan, National symp. on PersonalComputers in Science and Engineering, BARC, Bombay (1988)101 (Abstract).

34. A review of some stipulations in the radiation protectionmanual for nuclear facilities (Revision-2), M.P. Sankaran,Published by the Safety Review Committee of the Departmentof Atomic Energy, Bull. Radiat. Prot. 3, (3) (1987).

35. A need for national registry of radiation workers in India,P.K. Marathe, D. Krishnan, O.P. Massand and R.V. Dhond,Fifteenth IARP conference, Hyderabad, IARP/15/33(0), (1988).

36. Accuracy test of film badge dosimeters used in personnelmonitoring service, R.L. Pandey, A.S. Pathak, S.S. Hivarayeand P.H. Patel, XVth IARP Conference, Hyderabad (1988).

37. Analysis of high level radiation exposures of radiationworkers in medicine, industry and research institutions,R.L. Pandey, R.V. Dhond, P.H. Patel and S.J. Supe, XVth IARPConference, Hyderabad (1988).

38. Exempt quantities of radioisotopes for issuing personnelmonitoring dosimeters, R.V. Dhond, M.P. Sankaran, P.H. Pateland S.J. Supe, XVth IARP conference, Hyderabad, (1988).

39. Some recent incidents in radioactive well logging, ArunKumar, O.P.Massand, and G.Subrahmanian, Bull.Radiat. Prot.10(4), (1987) 21.

40. Investigations of the characteristics of some neutronmonitoring systems, O.P.Massand, Ph.D. Thesis, BombayUniversity, (1987).

41. Fast neutron personnel monitoring service, O.P. Massand,M.P. Dhairyawan, P.K. Marathe and H.K. Kundu, Fifteenth IARPconference, Hyderabad, IARP/15/92(S), (1988).

42. Calculation of spatial distribution of energy absorbed bybeta radiation in TL disk used for personnel monitoring,S.K. Gupta., R.K. Kher and S.J. Supe, Fifteenth Conference onRadiation Protection, Hyderabad (1988).

43. Use of computer in dose records maintenance, R. Sadagopan,Fifteenth Conference on Radiation Protection, Hyderabad,(1988).

44. Analysis of occupational exposure in nuclear industry, R.Sadagopan, P.H. Pardasani, S.J. Supe & P.H. Patel, FifteenthConference on Radiation Protection, Hyderabad, (1988).

45. Software development for compatability of works stations &personal computer in science & engineering, R. Sadagopan,National Symposium on Personal Computer, BARC (1988).

: 166 :

46. Safety requirements of remotely operated radiographyequipment, B.K.S. Murthy arid V.G.R. Subramanian, 15thConference on Radiation Protection, Hyderabad, (1988).

47. An analysis of radiation accidents in industrial radiographyduring the period 1982-87, V.G.R. Subramanian and P.Subrahmanyam, NAARRI Conf. Bombay (1988).

48. Emergency preparedness procedures for handling radiationaccidents in industrial radiography, V.G.R. Subramanian etal., Workshop for Radiological Safety Officers, Bombay(1988).

49. The need for adoption of a design safety standard fornucleonic gauge source housing, P. Subrahmanyam and S.P.Agarwal, 15th IARP Conf. Hyderabad (1988).

50. Radiation safety in luminous paint workshops, P.K. Gaur etal., National Conference on Industrial Applications ofIsotopes and Radiation Technology, Bombay (1988).

51. A radiation accident involving source pigtail detachment ina remotely operated gamma radiography equipment, B.K.S.Murthy and A.V. Lakshmipathy, 15th Conference on RadiationProtection, Hyderabad, (1988).

52. Modification of low level radiation induced genetic damageby environmental agents, B.S. Rao, K.B. Anjaria, N.Sankaranarayanan and U. Madhvanath, 14th L.H. Gray meetingon 'Low Dose Radiation-Biological Basis of Risk Assessment'at New College, Oxford, (1988).

53. Application of hyperthermia in the treatment of cancer, B.S.Rao, AMPI Med. Phys. Bull. 13 (1988) 161.

54. Role of repair and recovery processes in radiationcarcinogenesis, B.S. Rao, National Symposium on Biohazardsof Radiation, Jaipur, (1988) 6.

55. Induction of gene conversion in yeast exposed to combinationof beta and gamma radiation, B.S. Rao, K.B. Anjaria, N.Sankaranarayanan and U. Madhvanath, XVIth InternationalCongress of Genetics, Abstract. 31, 31.3. Ontario, Canada,(1988) 109.

56. Potential of hyperthermia in radiation therapy, B.S. Rao,First Afro/Asia/Oceania Congress of Anatomists, New Delhi,(1988) 81.

Published by Mead, Library & Information Services, BftRC, Bombay 400 085, India.