Review of international normatives for natural radioactivity determination in building materials

Anthropogenic activities, such as high-altitude flights and living in buildings, have enhanced the public exposure to natural radiation. In particular, ⁴⁰K and radionuclides belonging to ²³²Th and ²³⁸U decay chains are present even in building materials, and they may be considered as partially responsible for the effective dose coming from natural radioactivity. Scientists and governments have devoted great attention to the evaluation of the effects produced on the public by naturally occurring radionuclides. In this context, to evaluate the building materials acceptability, accurate and reliable methods for the measurement of the specific activity of natural radioactive isotopes in building materials have been developed. This paper aims to provide a clear and exhaustive review on natural radionuclide measurement procedures. Several standard national normatives (Dutch NEN 5697, Italian UNI 10797, Polish ITB 455), based on gamma spectrometry, have been considered and some critical issues were identified regarding the preparation and the radiometric measuring of the samples. Therefore, the direct measurement of ²³⁸U and ²³²Th by ICP-MS spectrometry as well as the extrapolation of the specific activities without waiting for secular equilibrium have been considered as two promising alternative approaches.