Overview of Activities on Reviewing Regulatory Issues in the Future System of Radiological Protection in Japan

The system of radiological protection developed by the International Commission on Radiological Protection (ICRP) provides the scientific and conceptual basis for regulatory frameworks worldwide, including that of Japan. Following the publication of the 2007 Recommendations (ICRP Publication 103), the system has continued to evolve in response to advances in scientific knowledge and changes in societal values. Recent international discussions, particularly those associated with the 7th International Symposium on the System of Radiological Protection (ICRP 2023), have highlighted the potential need for revisions to the existing framework and the introduction of new concepts. In this context, the Nuclear Regulation Authority of Japan commissioned a series of projects in fiscal years 2024 and 2025 to systematically review ongoing ICRP activities and to assess their potential impacts on the Japanese regulatory framework. This paper provides an overview of these projects and their key findings. Information from relevant ICRP task groups was collected and organized into seven thematic areas: (1) overarching theme on the system of radiological protection; (2) radiation detriment and classification of effects; (3) impacts of a new dose assessment system; (4) radiological protection of the environment; (5) reasonableness, tolerability, and justification; (6) exposure situations and exposure categories; and (7) individualization and stratification in radiological protection. A detailed investigation conducted in fiscal year 2025 focused on the impacts of a new dose assessment system. The results highlight the importance of clearly distinguishing between technical changes, which can be addressed through incremental regulatory revisions, and conceptual changes, which may require substantial amendments to existing laws and regulatory structures. The findings underscore the need for continuous monitoring of international developments and proactive nationallevel discussions to ensure the robustness and sustainability of radiological protection regulations in Japan.