Comparative analysis of offsite consequence results based on ICRP 26, ICRP 60, and ICRP 103 frameworks in level 3 PSA

In Level 3 probabilistic safety assessment (Level 3 PSA), offsite radiological risk is quantified through pathway-specific dose assessments based on atmospheric dispersion and deposition analyses. Dose coefficients play a critical role in this process by converting environmental radionuclide concentrations and intakes into estimates of human radiation doses, thereby directly influencing the results of offsite consequence analysis. This study evaluates the impact of three representative dose coefficient frameworks commonly applied in offsite radiological consequence assessment: those based on ICRP Publications 26, 60, and 103, issued by the International Commission on Radiological Protection, as well as a fourth framework based on Federal Guidance Report No. 13 (FGR 13), published by the U.S. Environmental Protection Agency. Offsite consequence simulations were performed using the RCAP and MACCS codes. Differences among the four frameworks were assessed in terms of spatial dose distribution, protective action distances, evacuation criteria, and emergency planning zone boundaries. The results indicate that the application of the ICRP 26-based framework generally produces higher dose estimates than the other three frameworks. Consequently, it leads to larger reference distances for the implementation of protective actions and the delineation of emergency planning zones. These findings demonstrate that the selection of a dose coefficient framework can meaningfully affect offsite consequence estimates, emergency-response decisions, and the overall reliability and comparability of Level 3 PSA results. They also indicate a potential need to reassess regulatory approaches that continue to rely on dose coefficients derived from ICRP 26.