Breaking the cycle of excessive conservatism: Evaluating the γ-radiation dose from building materials

Radionuclide content in building materials is regulated in most European countries by calculating the activity concentration index. The I-index does not account for the properties nor the application of the material but provides a conservative evaluation of the annual γ-radiation dose. Using a Monte Carlo toolkit, EGSnrc, this study calculated doses from building materials in less conservative set-ups by focusing on materials with a potential for recycling NORM residues, such as Portland cement, ceramics, gypsum, and mineral insulation. It was observed that proper consideration of building material geometry strongly affected the indoor dose rate. Regulating low-density materials and finishing materials such as gypsum and insulation under the same framework as high-density and high-bulk materials proved problematic because the doses differ by orders of magnitude. The current reference values for radionuclide concentrations used in calculating the I-index do not apply to most construction materials. For many types of building materials, higher radionuclide concentrations in the material could be allowed without contradicting the annual effective dose reference for the public. This illustrates the potential for boosting the use of NORM residues in various construction applications.