Inter-comparison exercise for determination of 226Ra, 232Th and 40K in soil and building material

A nationwide inter-comparison exercise for the determination of activity concentration of 226Ra, 232Th and 40K in soil and building material was organized by the National Institute for Radiological Protection (NIRP), CDC, China. The primary purpose of this work was to assess the accuracy and precision of γ-spectrometry analyses. Activity concentrations of 226Ra, 232Th and 40K were determined by gamma-ray spectrometry in accordance with established inter-comparison procedures. A total of 15 laboratories participated in this programme. All participants reported their comparison results for a total of 87 data sets for three nuclides in soil and building material. The overall measurement results of samples for inter-comparison showed a good agreement with the reference values, with nearly 87% of the participants producing acceptable results. Some influential factors in measurement comparisons are also discussed in this paper on the basis of reported results.