Inter-laboratory comparison within the RESORAD Italian network on the natural occurring radioactive materials (NORMs)

Environmental radioactivity monitoring is of fundamental importance not only in routine situations but also in the event of accidental occurrences, such as the Fukushima incident in 2011, and in extraordinary situations, such as those currently experienced in war-torn countries with nuclear facilities. In Italy, the National Network for Environmental Radioactivity Surveillance (RESORAD), coordinated by ISIN, oversees the reliability of environmental radioactivity measurements. ENEA-INMRI develops, maintains, and disseminates measurement standards and units in the field of radioactivity through inter-laboratory comparisons (ILCs), calibration campaigns, and performance evaluation tests. This work presents the results of an ILC conducted for RESORAD laboratories, called NORM-2021, organized within a scientific collaboration between ISIN and ENEA-INMRI. The initiative focused on the measurement of naturally occurring radioactive materials (NORMs). Specifically, the aim of the ILC was to identify and quantify NORMs in natural volcanic sand. To perform the ILC, ENEA-INMRI prepared a solid reference material (MRS) by collecting sand samples from seven distinct volcanic lake sites in the Lazio region. An artificial imbalance in the uranium radioactive series was introduced into the MRS to assess the analytical capabilities of the participating laboratories. The results were analysed using indicators commonly employed in performance evaluations and inter-laboratory comparisons [ISO, 2010; ISO, 2016].