Welcome to the PSAM 18 Abstract Status page.
Abstract ZH208Full Paper + Presentation
A Two-Layered Framework from Regulatory Safety Goals to Plant-Specific Performance Goals for Driving Continuous Nuclear Safety Improvement
Following the accident at Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Station, Japan introduced stringent new regulatory requirements. Consequently, probabilistic risk assessments (PRAs) conducted by Japanese utilities currently report core damage frequencies (CDFs) in the range of 10-6 to 10-5 per reactor-year. While these figures suggest that operating plants are exceptionally safe, they present a unique regulatory paradox. If a standard performance goal of 10-4 per year is established, it will be overwhelmingly satisfied by all operating plants, potentially rendering the goal obsolete as a driver for continuous safety improvement.
This situation raises a critical regulatory question: under conditions where evaluated risks are already substantially lower than international norms, how should performance goals be set? Relying on a static, uniform threshold risks fostering a new “safety myth,” where meeting the goal is misinterpreted as the completion of safety efforts. This fundamentally contradicts the risk optimization principles of ALARA and ALARP (as low as reasonably achievable/practicable).
To resolve this issue, this paper proposes a novel, hybrid framework for goal setting in Japan, drawing upon the rigorous optimization philosophies of the UK's ALARP principle and the USNRC's “two-tier” backfit rule. Specifically, we propose a two-layered regulatory architecture. First, the regulatory authority establishes top-down quantitative health objectives (QHOs) to serve as the upper limit of socially acceptable risk. Second, instead of setting uniform regulatory targets for CDF and containment failure frequency (CFF), each utility is required to propose bottom-up, plant-specific performance goals. These proposed goals must not only satisfy the regulatory QHOs but also be set on the stringently safer side of the plant’s own current PRA baseline results.
This plant-specific approach shifts the regulatory paradigm from simple threshold compliance to proactive risk optimization. By requiring utilities to propose and pursue safety enhancements that meet their self-imposed, ambitious targets, the framework effectively embeds the ALARA/ALARP principle within the Japan’s Periodic Safety Assessment of Continuous Improvement System. Furthermore, this mechanism incentivizes both utilities and regulators to continuously refine their PRA methodologies and safety culture, ensuring that safety goals function not as a free pass to halt improvements, but as a genuine driver for continuous risk reduction.
← Check another abstractThis situation raises a critical regulatory question: under conditions where evaluated risks are already substantially lower than international norms, how should performance goals be set? Relying on a static, uniform threshold risks fostering a new “safety myth,” where meeting the goal is misinterpreted as the completion of safety efforts. This fundamentally contradicts the risk optimization principles of ALARA and ALARP (as low as reasonably achievable/practicable).
To resolve this issue, this paper proposes a novel, hybrid framework for goal setting in Japan, drawing upon the rigorous optimization philosophies of the UK's ALARP principle and the USNRC's “two-tier” backfit rule. Specifically, we propose a two-layered regulatory architecture. First, the regulatory authority establishes top-down quantitative health objectives (QHOs) to serve as the upper limit of socially acceptable risk. Second, instead of setting uniform regulatory targets for CDF and containment failure frequency (CFF), each utility is required to propose bottom-up, plant-specific performance goals. These proposed goals must not only satisfy the regulatory QHOs but also be set on the stringently safer side of the plant’s own current PRA baseline results.
This plant-specific approach shifts the regulatory paradigm from simple threshold compliance to proactive risk optimization. By requiring utilities to propose and pursue safety enhancements that meet their self-imposed, ambitious targets, the framework effectively embeds the ALARA/ALARP principle within the Japan’s Periodic Safety Assessment of Continuous Improvement System. Furthermore, this mechanism incentivizes both utilities and regulators to continuously refine their PRA methodologies and safety culture, ensuring that safety goals function not as a free pass to halt improvements, but as a genuine driver for continuous risk reduction.