First intercomparison among laboratories involved in COST Action-TU1301 "NORM4Building": Determination of natural radionuclides in ceramics

This work describes the outcomes of the COST Action-TU1301 "NORM4Building" intercomparison on the determination of natural radioactivity in ceramics. Twenty-two laboratories involved in the intercomparison are evaluated for their performance using robust statistics. The reference values of ²²⁶Ra (²¹⁴Bi and ²¹⁴Pb) are determined to be 122 ± 11 Bq kg^-1 and 124 ± 14 Bq kg^-1, respectively and in secular equilibrium in the uranium chain while the reference values of ²³²Th (²²⁸Ac) is determined to be 61 ± 6 Bq kg^-1 and that of ⁴⁰K was determined to be 955 ± 40 Bq kg^-1. Although the aim of the exercise was to determine the activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K and evaluation of the "Activity Concentration Index", laboratories were asked to report complete characterization of natural radionuclides. The results of this exercise pointed out a good performance among laboratories since the percentage of the acceptable results were above 90% for the radionuclides of interest. Based on these results, considering the systematic rejection of the results reported from a few laboratories we emphasize the need for quality control procedures.