Assement of radionuclide concentration in various samples by gamma spectrometry and LSC

1. 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

2. TheLaboratory 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 implementedin our laboratory since the year 2000.

4. 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.

5. The measurements of high tritium activities in reactor basin and for monitoring contaminategroundwaterwere carried out with the liquid scintillation spectrometer Packard TRI-CARBusing the scintillation liquid OptiPhase “HiSafe”3.The measurement time for H-3 didn’t 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).

6. 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

7. HPGe gamma spectrometer

8. Efficiency of HPGe detectors

9. NaJ gamma spectrometer

11. Liquid scintilator spectrometer

13. iSOLO equipment for alfa and beta measurements

14. Methods For the measurements we use 15 methods. The most importent are: Determination of the radionuclides concentrationby high resolution gamma-rayspectrometry.T190-1-24-237-2004 Water quality – Determination of the activity concentration of radionuclides by high resolution gamma-rayspectrometry. LVS ISO 10703:2008. Water quality. Determination of the specificactivityof tritium. Liquid scintilation counting method. LVA ISO 9698:2003. Building materials quality – Determination of the radionuclides and specific activity of radionuclides in building materials bygamma-rayspectrometry. LVS ISO 257:2000.

15. 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 laboratory’s 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.

16. Quality assurance Quality SystemQuality 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

17. Participation of laboratory in the intercomparison exercises

18. Figure compares our results with the weighted mean in seaweed. There is a good agreement between them.

19. Column diagram of sum of z-scores for results from all radionuclides combined showing contributions from individual samples (No. 17-Laboratory of Radiation Physics).

20. 137Cs content in mushrooms in Latvia (1987)

21. 250 Bq/kg 200 150 100 50 0 1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101 106 111 Sample number Cs-137 radioactivity of soils in the 3 km zone of the Salaspils nuclear reactor

22. Shut-down medical facility Dubulti Boring of samples

23. Pollution with Ra-226 depending on the depthin Dubulti

24. Ra_226 concentration in the waste from Dubulti (in barrels)

32. Results of tritium detection in Latvia: Communal water sources – 155 objects 5 Bq/L < T < 10 Bq/L 0,01 Bq/l < α < 0,2 Bq/l 0,1 Bq/l < β < 0,6 Bq/l Water for food industry – 54 objects 5 Bq/L < T < 10 Bq/L 0,01 Bq/l < α < 0,05 Bq/l 0,1 Bq/l < β < 0,4 Bq/l

34. 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.

35. Thank you for your attention Thank you for your attention