In this study, we propose rational and simple safety requirements that can be applied to new light water nuclear power reactors on the basis of the concept of current regulatory requirements. By introducing a “new design-basis accident response system” with diversity and “division completeness” from the design stage, it will be possible to integrate the conventional “Design-basis accident response system,” “Severe accident prevention system,” and “Severe accident mitigation system.” This significantly reduces the risk of common-cause failures. The functional objectives of “Specified Severe Accident Response Facilities” are also incorporated into the new system, with the diversity division responsible for these functions. Severe accidents, defined as extremely rare events that exceed design conditions, require flexible countermeasures. These include a combination of static equipment with safety margins and mobile equipment. The safety requirements discussed in this study are primarily applied to large light water nuclear power reactors, but they can also be applied to future nuclear power reactor developments such as small modular reactors (SMRs), contributing to improved design efficiency, shorter construction periods, faster reviews, and cost reductions. The proposed safety requirement framework supports the development of next-generation reactors that can achieve both decarbonization and energy security.
Uemura et al. (Thu,) studied this question.