Determination of natural and anthropogenic radionuclides in soil—results of an European Union comparison

A comparison was organised by the Institute for Reference Materials and Measurements (IRMM) among 73 environmental radioactivity monitoring laboratories for the determination of 15 radionuclides in soil. The reference material IAEA-375 soil was reprocessed to provide the comparison material and reference values traceable to SI units and SIR were established at IRMM. The analytical procedures used by participants laboratories are discussed and performances evaluted using relative deviations and En numbers. This paper focuses on the results for 40K, 90Sr, 137Cs, 226Ra, 234U, 235U and 238U. Worst performance was found for 90Sr and 235U, where 65% and 78% of the results, respectively, deviate more than 20% from the reference values. The use of the En criterion revealed that the uncertainty estimation of many participants is poor. ► Interlaboratory comparison among laboratories monitoring environmental radioactivity. ► Reference values traceable to SI units and SIR were established at IRMM. ► Results for radionuclides 40K, 90Sr, 137Cs, 226Ra, 234U, 235U and 238U are presented. ► Worst performance is found for 90Sr (65% off by>20%) and 235U (78% off). ► En criterion revealed that the uncertainty estimation of many participants is poor.