NUCLEAR REGULATORY COMMISSION PROBABILISTIC RISK ASSESSMENT IMPLEMENTATION PROGRAM A STATUS REPORT

摘要

The U.S. Nuclear Regulatory Commission (NRC) is undertaking a number of activities intended to increase the consideration of risk significance in its decision processes and the effective use of risk-based technologies in its regulatory activities. Although the NRC is moving toward risk-informed regulation throughout its areas of responsibilities, this paper focuses primarily on those issues associated with reactor regulation. As the NRC completed significant milestones in its development of probabilistic risk assessment (PRA) methodology and gained considerable experience in the limited application of risk assessment to selected regulatory activities, it became evident that a much broader use of risk- informed approaches offered advantages to both the NRC and the U.S. commercial nuclear industry. This desire to enhance the use of risk assessment is driven by the clear belief that application of PRA methods will result in direct improvements in nuclear power plant operational safety from the perspective of both the regulator and the plant operator. The NRC believed that an overall policy on the use of PRA methods in nuclear regulatory activities should be established so that the many potential applications of PRA could be implemented in a consistent and predictable manner that would promote regulatory stability and efficiency. Such a policy was established in the NRC policy statement on "Use of Probabilistic Risk Assessment Methods in Nuclear Regulatory Activities" (60 Federal Register (FR) 42622, August 16, 1995), and the NRC staff is executing the policy under an implementation plan. The broad implementation plan covers applications in the nuclear materials area as well as power reactor applications. The NRC staff is interacting with the nuclear industry on the following power reactor applications: 1) maintenance rule and on-line maintenance 2) graded quality assurance and other risk-ranking applications 3) risk-informed technical specifications Other important ongoing activities covered by the implementation plan include the following: 4) development of a general framework for risk-informed reactor regulation, including appropriate PRA standards 5) development of an integrated performance assessment process for nuclear power plants 6) reviews of individual plant examinations 7) application of risk assessment techniques to the evaluation of human performance in the use of medical radiation devices 8) application of risk assessment techniques in the evaluation of methods of storing nuclear waste This paper describes the key activities that the NRC has undertaken to implement the initial stages of an integrated risk-informed regulatory framework.