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U.S. DEPARTMENT OF COMMERCE National Instihte of Standards and Technotogy

Gpmsored by the Office of HeJth and EnvironmcW.l Research, DOE Contract Number . DE-A102-?H€R&l528, NfST &st Center Number $460473.

PROJECT OWECllVfiS

“. To obtain inbmatlon about the physical stage of neutron interadions with tissue thmugh secondary charged partldes. We w e theoretical Calculations whose input indudes neutmn

. or088 SSdiOn data; range. stopping power, ion yield and, straggling InfomWIan: and geometrical ptoperth. Outputs am Snitid‘ and LSlt)Wjng-down’ spedra of Gharged particles, kerma factors, average values of quality forctors, micradosimetric spectra, and integd microdosimeMc par”~uneten such as y,, yo, $. Since h has b m e apparent that nanometer site sizes are more relevant to radiobialogicat effects, the c a l d o n a of event size s p e ~ t m and their p a v t e r s have been extended to these smaller diameters. This ’ . @foamration is basic to rabitjfqiwl physics, radiation bidogy, radiation protection d wcrr)cers; and standards for neutron dose measurement.

ACWMPUSHMWS .

Katz used neutron-induced secondary partkle.spectra to predict cellular neutron effects by delta-~ay interaction model

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y speotm wwe as standard for health physics andysia nf mdlatbn fields wing . a -

tissueequivalent gwportionai counters {etatmfthe-art’meWmd)

Neutron code led to radon code. W, Hofmann (U. crf Wzburg} urns our results vrith his effect-speciflo track-length model to predict radbn cardnogeneds in bmnchid eptUlslIum

Ttadc etnrchrre effecbin neutran micmdosimdry and nanodrnlmky, This is an invs~gation of the effect of pmta energy-ibss straggling and the assodated ttansport of energy by seccandary electmns on neutron event-size distcibutions in small Sites. W. Wilson of Pacific Northwest Labomtey and H, Parehke of QSF, Munich have developed an a w c model tor the IonitatianS or energy depositions produced In nanmeter-size skslar pmmns and alpha partieies which summarizes the results of hundreds of Monte Carlo calculatiuns. The Wilson-PareM modes has been used to generate ewntsize dlsrribukms for monosnerge€ic protons with 8 given chord length within 8 sphere of h d diameter- Their

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government Neither the United States Government nor any agency thenof, nor any of their cmployecr makes any wuranty. exprey or implied. or assumes any legal liability or responsibility for the accuracy, cornpietentsf or w- fuiness of any information, apparatus, pr#iuct, or pnxxss d i s c i d or represents that its use would not infringe privatdy ow& rights. Reference herein to any spc- cific commercia1 product, process. or service by trade name, trademark, manufac- turer, or otherwise does not neccuarily constitute or impiy iu endorsement. recam- mendation. or favoring by the United States Government or my agency thcmf. The views and opinions of authors expressed h m i n do not n d l y state or reflect those of the United States Governmat or any agency thenof.

DISCLAIMER

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

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cfiatribufi~ls have heen fitted wlfh log n a m i dfstrlbution fundonk and the parametere of the fog normal function are fitted analytically as a function of pmton wargy, sphere dlameter, and chord length. ' These proton spectra are then used in a modified Cwwefl-Coyne code to . generate event-size distributions for .mitrons whids indude not only the effect of 9~8fgy-kss sti'ag~fing but alsd the transpofl of energy au2 of and into the gavity by #e' s m d a r y delta rays. @llsOn and Parekke have also.at?dyzed data 'for ' t ~ ~ & e t s ~ or

. 'pasaem' for ppfona and these ani ipcluded in our mkxWbrsM well.

' It has been dear for some time'that, although We cell nut2Ieu.s Is of the scale of'miisrons;, say . 8 VM, td underetand the biological effeats of ibnWrrg radiations we need to conaickr as well

smallBr structures wctl a6 .DNA (2 nm spacing between the. strands) and nudeo$ornes (5-1 0 nm), For neutrons the situation is more wmpllcated than for pratans, for example, because of the many geConrJa,ry partioles produced, by neWn interactions,& most important being

U$ing the ~Ison-Pareke &del combined with bur a$ytic nwfron code, we have caloulafed the specha d neutron energy deposltlons in nanonteter-&e cavities fot neutron .energies from 0.5 MeV to 20 MeV,. Mest af our ckidmlations 'are for site sizes ranging from 1 o nm to IOOO; nm. we are etudying fie question of what is th meaning of an energy

'depw*tion spectrum for site sizes as s m d a i 2 nrn, perhaps oniy ionization frequency . needs to be considered. O'ur latest work hac been summarjzt?d in a paper, Randall S. C a w j l and Stephen Mt Sdtrer, 'MJlpnte Garto and Analytic Methods in the Tramport af Eieotrorrs,,, Neutrons, and Alpha Particles' which is to be published In the Proceedings of the. '

. Monte Carlo Workshop, held April 27-2!3,1383 in lrvine . . California (Plenum Pre6s).

We are also making $oms cornpansons of results with other calculations (Morstln ahd Ofko)

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p, U, C,.N, and 0. . .

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and expen@mtd measurernsnk (Kliauga). . . The m p u t e r program L opemhal on 'bath the CmyY-MP and Gamrex'Ca82~ computers

, at NET, arthcigh the . . Ctay.& pteeferred bemutie d the greabr speed and longer ward . . m g W . . - .

' Enemy depos@m spectm md their moments fqr fast neutrons. Using calculated chiuged partide initial 8pea.n arid stdwingdawh spectra wa'c~.calculate ttre energy deposition. in spherical cavities, The spectrum Qbbined is sometimes called the single event

. hip- or a distribution of dask velsus y, the lined energy. The frequency mean of this spectrum, yFI the dose avarage, pa, and the dose averageincluding eaturatian.comction, y?, ; can then be calculated. fhese quantities-are closely related la the' Kslkrer-Fzwsi

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parameters&, 5, and (, We calculate these apeclG and thelr rnwnents for neutron enetyles up tR i3l MeV and for wily sizes in the range of '5 pm fa 30 prn Syaematic calwlatlons have been carried cyt ofathe energy depodtim spectrum, fT(c), and the

, parameters pF, yo, and ye over the range di energies and ssnsltie volume, skes cited using 'bin-averaged neutmrl c16w mctlonsI .

Study of ReJation to Bld8gy and Biophysical Models af Nsutron Bmrgy DeposWtian CalwlaHans, Stephen M. Seltzer, who le well-known in the fldd of radlatlon transport

I . aaloulations, and Lisa R.. mrn, who has h a d experi,ence in @&ation biochemistry, and R.

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S. Cawell, dl pakciphtsln this projeci have formed a.&dl. study group biophydml and b i d e m i d r'rfodels of radiation interaction. Dr. k r a m ip teaching the tvvo ph@d&ts mfecul~ biology and radiation biochemistry, .and Seltzer and Caswll are discussinga . heutron microdudmetry, neutm nanododmetry. and bkphysloaf modele of radiation interactm. We dsa interact with hfessor Werner H~fmrutn fmm the univaf&ib, of $akburg.on bbphmicaf models of radiation cadnogenesis, which ars primarily for the radon problem, but ;ue relevant to n e u m health efbas. Steve Sbltzerb- reported on the Lethal, Pbtentialfy Lethal (1PL) rltOdel of Stan Curtis to a $diem Subpanel of the 3

Gommitteeon fnteragsncy Radlatbn Research and Policy Cootcanation (CIRRPC) studying RuenceBased Risk Aw&ment. These discussions: have been exceedingly internsting so far, an4 we anticipate that they wlfl 'bad ta signiflean€ insight into the biologid e- d a

ionizing radiation and to new apprqaches to the subjaot of 'Neutron Interac#ons wiRh Biological Tfssue'.

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RECENT PUkUCATlONS , ' . . .

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9. Hofmann, W., Nlisterer, M., Menache, M. a,, Crawford-Brown, D, ELl Gaswell, R S. I

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IO. . Cawell, R S. and Sehzer, S. M., 'Monte Carla and Analytic Methods in the Transport af Electrons, Neutrons, and Alpha PaRides", RoceedCngs of the

. Wotkshrbp MI Ma- Carla Methods in h;rck StruWre, Plenum. P ~ S B (in ptese).

-1 1. Caiswefl, R S., "Neutron Mmefty; Past and Present,' M e # R e s h e r Coma Series, Watien Research Society 42nd Annual Ncecting, Naihvliie; Tennessee, 4 May, 1994.

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"These are applications df the analytic method developed for neutrons to the problem of radon. . 1

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