Handbook of methods for risk-based analysis of technical specification requirements

Technical Specifications (TS) requirements for nuclear power plants define the Limiting Conditions for Operation (LCOs) and Surveillance Requirements (SRs) to assure safety during operation. In general, these requirements were based on deterministic analysis and engineering judgments. Experiences with plant operation indicate that some elements of the requirements are unnecessarily restrictive, while others may not be conducive to safety. Improvements in these requirements are facilitated by the availability of plant specific Probabilistic Safety Assessments (PSAs). The use of risk and reliability-based methods to improve TS requirements has gained wide interest because these methods can: Quantitatively evaluate the risk and justify changes based on objective risk arguments; Provide a defensible basis for these requirements for regulatory applications. The US NRC Office of Research is sponsoring research to develop systematic risk-based methods to improve various aspects of TS requirements. The handbook of methods, which is being prepared, summarizes such risk-based methods. The scope of the handbook includes reliability and risk-based methods for evaluating allowed outage times (AOTs), action statements requiring shutdown where shutdown risk may be substantial, surveillance test intervals (STIs), defenses against common-cause failures, managing plant configurations, and scheduling maintenances. For each topic, the handbook summarizes methods of analysis and data needs, outlines the insights to be gained, lists additional references, and presents examples of evaluations