Results Assessment of Intercomparison Exercise CSN/CIEMAT-2010 among Spanish National Laboratories of Environmental Radioactivity (Diet Ashes)

This report describes the results assessment of the intercomparison exercise among environmental radioactivity laboratories, organised by Spanish Regulatory Institution (CSN) and prepared and evaluated by UAB and CIEMAT respectively. The exercise has been carried out following the international standards ISO-43 and ISO/IUPAC that provide a useful guide to perform proficiency tests and inter-laboratories comparisons. The selected matrix for this year (2010) was a diet ash obtained from the ashing of a whole fresh diet (breakfast, lunch and dinner), that was enriched with artificial radionuclides (Cs-137, Co-60,Fe-55,Ni-63,Sr-90,Am-241,Pu-238,Pu-239,240 y C-14) and contained natural radionuclides (U-234, U-238, U-natural Th-230, Th-234, Ra-226, Ra-228, Pb-210, Pb-212, Pb-214, Bi-214, Ac-228, Tl-208, K-40) at environmental level of activity concentration. The z-score test was applied to determine how much the laboratories differ from the reference value. The reference value for this exercise was the median of the results from the different laboratories and their standard deviations to achieve a more complete and objective study of the laboratories performance. The participant laboratories have demonstrated a satisfactory quality level for measuring the natural and artificial radionuclides content in this matrix. The reference values obtained through the medians show a negative bias for Pb-210 and Th-234 when comparing to the given values of external qualified laboratories from ENEA and IRSN and positive one for K-40. (Author)