PRA PEER REVIEW FINDING CLOSURE VIA INDEPENDENT ASSESSMENT

摘要

A process has been developed for performing a focused scope independent assessment to review close out of "Finding" level Facts and Observations (F&Os) of record from prior Probabilistic Risk Assessment (PRA) peer reviews against the ASME/ANS Standard.' The results of this independent assessment will be used to support future License Amendment Request (LAR) submittals. F&O dispositions reviewed and determined to have been adequately addressed through this technical review process will be considered as "closed" and no longer relevant to the current PRA model, and thus need not be carried forward nor discussed in future LAR submittals. The process generally follows the applicable guidance defined in Nuclear Energy Institute (NEI) 05-04, Rev.3 (Process for Performing Internal Events PRA Peer Reviews Using the ASME/ANS PRA Standard); NEI 07-12, Rev 1 (Fire Probabilistic Risk Assessment (FPRA) Peer Review Process Guidelines); and NEI 12-13 Rev.O (External Hazards PRA Peer Review Process Guidelines). Although those processes were developed for use in performing peer reviews of Technical Elements of the PRA, rather than performing reviews of the resolution of prior peer review finding level F&Os, the NEI documents provide a solid foundation for performing these independent assessments. Performance of independent assessments of F&O resolutions via this process is encouraged by the Nuclear Regulatory Commission (NRC). The results of this process should obviate the need for NRC review of PRAs allowing the NRC review of LARs to focus on application specific impacts, key assumptions, and areas identified by the peer review as being of concern. The process has been applied to several plant independent assessment finding closure reviews to date with several more planned for the near term. Insights from the technical reviews conducted on Exelon plants as of this writing (Limerick, Peach Bottom, Braidwood, Byron) are summarized in this paper.