A new certified reference material for NORM in mineral aluminium ore (bauxite) - IAEA-493

The IAEA Terrestrial Environmental Radiochemistry (TERC) Laboratory supports Member States (MS) laboratories in enhancing the reliability of analytical measurement results through the provision of Reference Materials (RM), which can be used for the evaluation of measurement procedures, calibration, and for quality control purposes. Radioactivity monitoring in the vicinity of mines, industrial facilities, and waste disposal sites is one of the tasks of testing laboratories, and the Certified Reference Material (CRM) IAEA-493 was produced to support this task at MS laboratories worldwide. Bauxite is a mineral ore used mostly for aluminium production and can be considered as Naturally Occurring Radioactive Material (NORM). Processing of bauxite can disturb the natural radiological burden of the environment and reliable radionuclide content determination is of crucial importance for environmental studies. TERC is accredited to produce CRMs (ISO 17034) and production of IAEA-493 was in line with the standard's requirements. Sampling, homogenization, bottling, bulk homogeneity measurements, and a feasibility study were conducted in the IAEA Collaborating Centre - Radioanalytical Reference Laboratory, National Food Chain Safety Office, Hungary. Homogeneity and stability studies were performed in TERC. Characterization was performed by gamma-ray spectrometry in TERC and assigned values for ²³²Th, ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³⁵U, ⁴⁰K, and ¹³⁷Cs activity concentration were confirmed by results reported from the expert laboratories who participated in the characterization study. Alpha-particle spectrometry of uranium isotopes performed in TERC additionally confirmed assigned values for these radionuclides. IAEA-493 was also used as a sample in TERC's Worldwide Proficiency Test (PT) Exercise in 2024. The description of the CRM production and certification of activity concentrations of naturally occurring radionuclides in IAEA-493 is presented in this paper.114670.