Assement of radionuclide concentration in various samples by
gamma spectrometry and LSC J. Berzins, D.Riekstina, O. Veveris
Institute of Solid State Physics University of Latvia Dresden
2010
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The Laboratory was organized as the group of the Laboratory of
nuclear reactions in 1986 after the accident in Chernobil NPS with
the aim to control via gamma spectrometry the environment and
measure the radioactivity in foodstof and other samples. Since 1998
the group was reorganized to the Material radioactivity testing
laboratory. The quality assurance system was implemented in our
laboratory since the year 2000.
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Different contaminate samples: soils, waters, metal scrap and
various types of samples, irradiated in the research nuclear
reactor, were measured by gamma spectrometer. The concentrations of
radionuclide were determined using the high resolution HPGe gamma-
spectrometer type Ortec within the energy range of 50- 2000 keV.
For measuring of large radioactive waste volums in the metal
barrel, gamma-spectrometer with NaJ detector were used. The
uncertainty of measurements was within the range of 3-10%, but the
minimal detectable activity 0.3 Bq/kg.
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The measurements of high tritium activities in reactor basin
and for monitoring contaminate groundwater were carried out with
the liquid scintillation spectrometer Packard TRI-CARB using the
scintillation liquid OptiPhase HiSafe3. The measurement time for
H-3 didnt exceed some hours and uncertainty was less than 2%. The
credibility of obtained results is ensured by the quality assurance
and control. The main requisitions involved in the quality
assurance of the laboratory according to the requirements of
ISO/IEC 17025:2005 are: 1) the use of calibrated equipment only; 2)
the regular long-time use of reference materials for the control of
equipment; 3) the regular participation in the interlaboratory
intercomparison exercises, organized by the RISO National
Laboratory (Denmark) and IAEA (Vienna).
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Measurements Free release of reactor materials Monitoring for
potentially contaminated territories Water quality control Customer
service J-131 from hospitals - metal scrap from foreign countries -
samples from illegal radioactive material transport
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HPGe gamma spectrometer
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Efficiency of HPGe detectors
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NaJ gamma spectrometer
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Liquid scintilator spectrometer
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iSOLO equipment for alfa and beta measurements
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Methods For the measurements we use 15 methods. The most
importent are: Determination of the radionuclides concentration by
high resolution gamma-ray spectrometry. T190-1-24-237-2004 Water
quality Determination of the activity concentration of
radionuclides by high resolution gamma-ray spectrometry. LVS ISO
10703:2008. Water quality. Determination of the specific activity
of tritium. Liquid scintilation counting method. LVA ISO 9698:2003.
Building materials quality Determination of the radionuclides and
specific activity of radionuclides in building materials by
gamma-ray spectrometry. LVS ISO 257:2000.
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Our internal quality audit program covers all requirements of
ISO/IEC 17025:2005 standard, but the main attention is paid to the
analysis of results of laboratorys participation in intercomparison
measurements, their evaluation, interpretation and determination of
uncertainty sources. Since 1999 laboratory is a regular participant
in the interlaboratory intercomparison exercises organized by the
RISO National Laboratory (Denmark) and IAEA (Vienna). Such nuclides
as K-40, Mn-54, Co-57, Co-60, Zn-65, Cs-134, Cs-137, Eu-152,
Ra-226, U-238 and Th- 232 were analyzed in following
intercomparison samples: soils, sediment, seaweed, aerosol, grass,
hay, meat, dray milk, waters.
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Quality assurance Quality System Quality control Experienced
staff Use of standard samples Premises, surroundings Measurement of
background Validated methods Analysis in duplicates Calibrated
equipment Control charts: background, standard peak stability
Calibrated standards Reference materials Internal audit Staff
training Participation in intercalibration
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Participation of laboratory in the intercomparison exercises
YearOrganizerObjectRadionuclides 1999Risoe National laboratory,
Denmark Sediment, milk, meat, seaweed, hay K-40, Mn-54, Co-60,
Cs-137, Ra-226, Th-232 2000Risoe National laboratory, Denmark Milk,
aerosols, soil, seaweed K-40, Cs-137, Co- 60, Mn-54, Ra-226, Th-232
2002IAEA, ViennaMineral matrixMn-54, Co-57, Co- 60, Cs-134, Cs-137,
Eu-152 2003Risoe National laboratory, Denmark milk, mineral matrix,
seaweed Cs-137, K-40 2004- 2005 Risoe National laboratory, Denmark
Sediment, soil, seaweed K-40,, Cs-137, U- 238, Th-232 2006IAEA,
ViennaSoil, grass, waterK-40, Mn-54, Co-60, Zn-65, Cs-134,
Cs-137
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Figure compares our results with the weighted mean in seaweed.
There is a good agreement between them.
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Column diagram of sum of z-scores for results from all
radionuclides combined showing contributions from individual
samples (No. 17-Laboratory of Radiation Physics).
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137 Cs content in mushrooms in Latvia (1987)
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21 Cs-137 radioactivity of soils in the 3 km zone of the
Salaspils nuclear reactor 0 50 100 150 200 250
16111621263136414651566166717681869196101106 111 Sample number
Bq/kg
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22 Shut-down medical facility Dubulti Boring of samples
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Pollution with Ra-226 depending on the depth in Dubulti
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Ra_226 concentration in the waste from Dubulti (in
barrels)
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Results of tritium detection in Latvia: Communal water sources
155 objects 5 Bq/L < T < 10 Bq/L 0,01 Bq/l < < 0,2 Bq/l
0,1 Bq/l < < 0,6 Bq/l Water for food industry 54 objects 5
Bq/L < T < 10 Bq/L 0,01 Bq/l < < 0,05 Bq/l 0,1 Bq/l
< < 0,4 Bq/l
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Conclusions The use of gamma and beta spectrometry methods
allow: establish the pollution level in the territories included in
the monitoring decrease during the last years however unexpected
changes was detected; identify and evaluate the wastes of various
origin; control the quality of drinking water according to the
Latvian Cabinet of Ministers regulations No.235, adopted in 2003,
provision the entry in force of the EU Council Directive 98/83/EC.
Only credible and justified results can be the basis for further
use in any field, thus making it possible to make legitimate
decisions.