RESULTS OF THE 1997 98 INTERLABORATORY COMPARISON ON THE DETERMINATION OF I-131 IN MILK/

Following the accident in Chernobyl in 1986 the number of equipments a vailable for monitoring radioactivty, especially for gamma spectrometr y, has been increased considerably in the Federal Republic of Germany. Futhermore, new legislation requires that all official monitoring lab oratories verify the quality of their analytical technique by particip ating in interlaboratory comparison studies organized by Federal insti tutions. Such a study was therefore organized in 1997/98 by the Instit ute of Chemistry and Physics at the Federal Dairy Research Centre Kiel . 79 laboratories collaborated on the analysis of I-131 in milk. This paper describes the statistical evaluation of 101 sets of data for I-1 31, 15 sets for I-131 pre-concentrated with an anion exchange resin an d 60 sets for K-40. As expected the results of the study were good. Af ter eliminating a few discordant data, the average deviation of the la boratory means from the overall mean was 5.5 % for I-131: 7.0 % for pr e-concentrated I-131 and 4.0 % for K-40. Such good results imply that experienced personnel are efficiently operating modern sophisticated e quipment and software.