The transition to a circular economy promotes using industrial by-products, such as Naturally Occurring Radioactive Materials (NORM) residues, in building materials, necessitating a proper evaluation of radiological risks. To this end, the European Basic Safety Standards Directive (EU-BSS) established a regulatory framework for natural radioactivity, setting a reference level of 1 mSv/year for indoor gamma exposure. It introduced the activity concentration Index (I); if I > 1, a detailed dose assessment considering material characteristics (e.g., density, thickness) is required. Since the EU-BSS does not prescribe calculation methods, the EN 17637:2022 standard was developed to provide a harmonized approach. However, alternative methods exist, including point-kernel codes (MicroShield, RESRAD-BUILD) and Monte Carlo simulations. This study critically compares these methodologies to assess their reliability. Effective dose rates were calculated per unit activity concentration over a wide range of mass per unit area (up to about 1500 kg m−2) for all relevant radionuclides to facilitate direct comparison. The analysis reveals that EN 17637 standard aligns well with other point-kernel methods for mass per unit area below 500 kg m−2, with differences generally remaining within 10–20%. However, beyond this threshold, the standard assumes a dose plateau, whereas all other models indicate a continued increase in dose. Monte Carlo (MCNP) simulations yield dose estimates up to 54% higher specifically for Th-232, primarily driven by the choice of dose conversion factors and the inclusion of cross-wall scattering, which is inherently omitted in point-kernel models. Notably, when assuming isotropic geometry or excluding specific conversion factor influences, these overall differences generally fall below 15–20%. The study demonstrates that while EN 17637 remains an essential tool due to its simplicity, its accuracy for high-density materials can be improved by applying some adjustment factors proposed in this work.
Comparison of different methods for the assessments of effective dose due to gamma radiation emitted by building materials
Imparato C.;
2026
Abstract
The transition to a circular economy promotes using industrial by-products, such as Naturally Occurring Radioactive Materials (NORM) residues, in building materials, necessitating a proper evaluation of radiological risks. To this end, the European Basic Safety Standards Directive (EU-BSS) established a regulatory framework for natural radioactivity, setting a reference level of 1 mSv/year for indoor gamma exposure. It introduced the activity concentration Index (I); if I > 1, a detailed dose assessment considering material characteristics (e.g., density, thickness) is required. Since the EU-BSS does not prescribe calculation methods, the EN 17637:2022 standard was developed to provide a harmonized approach. However, alternative methods exist, including point-kernel codes (MicroShield, RESRAD-BUILD) and Monte Carlo simulations. This study critically compares these methodologies to assess their reliability. Effective dose rates were calculated per unit activity concentration over a wide range of mass per unit area (up to about 1500 kg m−2) for all relevant radionuclides to facilitate direct comparison. The analysis reveals that EN 17637 standard aligns well with other point-kernel methods for mass per unit area below 500 kg m−2, with differences generally remaining within 10–20%. However, beyond this threshold, the standard assumes a dose plateau, whereas all other models indicate a continued increase in dose. Monte Carlo (MCNP) simulations yield dose estimates up to 54% higher specifically for Th-232, primarily driven by the choice of dose conversion factors and the inclusion of cross-wall scattering, which is inherently omitted in point-kernel models. Notably, when assuming isotropic geometry or excluding specific conversion factor influences, these overall differences generally fall below 15–20%. The study demonstrates that while EN 17637 remains an essential tool due to its simplicity, its accuracy for high-density materials can be improved by applying some adjustment factors proposed in this work.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
