Document: NUREG-0800
Document ID: 7916b088-fb90-4163-84fe-027bd315bcc5
Document Type: srp
Title: REVIEW OF RISK INFORMATION USED TO SUPPORT PERMANENT PLANT-
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0717/ML071700658.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.2
CFR Part: 
CFR Title: 

Content:
ed initiators, the acceptable approach is to proceed on the basis of a structured representation of plant response that shows at least qualitatively the initiating events that may pertain, the systems available to respond to each, the functional dependencies of these systems, and the backups available in the event of failure of any particular SSC. While it is possible to accept program reductions for SSCs that are explicitly shown to play no role in unanalyzed modes, it is more difficult to accept reductions for components that do play a role in unanalyzed (e.g., shutdown) modes. For such instances, conservative methods will be considered prudent. To address instances in which a PRA model exists but is considered misleading, caution is indicated. An example would be to down-classify SSCs from a PRA result (i.e., state that a high risk contributor is actually a low contributor), on the basis of panel judgment. It is not acceptable to place on the record both a PRA and a finding that clearly contradicts it. Although the panel is not expected to take the PRA as absolute truth, the test should be whether the record establishes a clear basis for a finding. A technical argument that begins with the misleading PRA result and furnishes supplementary information sufficient to justify a relatively minor change to a PRA result, or a qualified interpretation of a PRA result, is satisfactory. A cursory technical argument leading to a conclusion that qualitatively contradicts a major PRA result is an unsatisfactory record. c. Evaluation Findings Reviewers should verify that information provided and review activities conducted support the following conclusions: • The integrated decisionmaking process is appropriate. Appropriate information was available, suitable issues were raised, the disposition of these issues was systematic 19.2-73 June 2007 and defensible, and the documentation of the findings is traceable and reviewable in principle, so that the basis for conclusions and