RESULTS OF THE 1993 INTERLABORATORY COMPA RISON ON THE DETERMINATION OF GAMMA-RADIONUCLIDE, SR-90, PU-238 AND PU-239 IN SOIL IN 1995 96/

Following the accident in Chernobyl in 1986 the number of units availa ble for monitoring radioactivity, mainly for gammaspectrometry, has be en increased considerably in the Federal Republic of Germany. Futhermo re, new legislation requires that all official monitoring laboratories verify the quality of their analytical technique by participating in interlaboratory comparison studies organized by Federal institutions. Such a study was therefore organized in June 1995 by the Institute of Chemistry and Physics at the Federal Dairy Research Centre in Kiel. 74 laboratories collaborated on the analysis of Co-60, Cs-137, K-40, Sr- 90, Pu-238 and Pu-239 in soil. This paper describes the statistical ev aluation of 92 sets of data for Co-60, Cs-137, 88 for K-40, 37 for Sr- 90 and 21 for Pu-238 and Pu-239. The results of the study were as good as expected. After eliminating only a few discordant data, the averag e deviation of the laboratory means from the overall mean was 5,6% for Co-60, 5,8 % for Cs-137, 4,7 % for K-40, 12,6 % for Sr-90, 5,2% for P u-238 and 19,8 for Pu-239. Such good results, except for Pu-239, are a ttributed to the reliability of the detectors, evaluation software, an alysis methods and to the skill of the laboratory staff.