Results of the joint IAEA/EEAE Intercomparison exercise on radioanalytical characterization of NORM samples in the European region.

Naturally Occurring Radioactive Material (NORM) may pose radiological risks across various industrial processes. Characterizing NORM is challenging due to radionuclide diversity, complex material matrices, and the multiple analytical techniques required. This study documents an Intercomparison Exercise (ICE) on the radioanalytical characterization of NORM, organized by International Atomic Energy Agency and EEAE to evaluate participants' abilities to implement appropriate radioanalytical techniques and promote harmonization, thus contributing to ongoing optimization efforts into radiation protection of workers and the public. Thirty-one laboratories from 21 countries participated and determined the activity concentrations of long-lived radionuclides such as 40K, 238U, 226Ra, and 232Th in two ICE items, most through gamma spectrometry. Improper handling and insufficient testing of equilibria status within uranium and thorium series were key sources of unsatisfactory results. Notably, laboratories' accreditation status did not correlate with analytical accuracy. Overall, study findings highlight improvements are needed in sample preparation, assumptions' validation and measurement uncertainty budget estimation procedures.