Measurement comparisons of radioactivity among European monitoring laboratories for the environment and food stuff.

For more than 15 years, European Union (EU) laboratories monitoring environmental radioactivity have been obliged to participate in measurement comparisons organised by the European Commission. After a short review of comparisons conducted during the 1990s, the approach of IRMM organising these comparisons since 2003 is presented. It relies on the provision of comparison samples with reference values traceable to the International Reference System for radionuclides (SIR). The results of the most recent comparison, the determination of (40)K, (90)Sr and (137)Cs in milk powder, are presented. The influence of repetitive participation in measurement comparisons on laboratory performance is studied on the basis of data from more than 20 laboratories having participated in several exercises during the last 15 years.