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
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CFR Title: 

Content:
bilities. b. Review Guidance and Procedures Reviewers should verify that the PRA addressed potentially significant CCFs and that, where applicable, the CCF modeling has incorporated the effects of the proposed changes. The staff evaluation should include a review of the process used to select common cause component groups. Specific review guidelines related to risk-informed applications and the assessment of the change are as follows: • Reviewers should verify that industry and especially plant-specific experience involving the failure of two or more components (especially for the application-specific components) from the same cause was analyzed and incorporated into the risk model where appropriate. • For relevant applications, reviewers should check that licensees have appropriately modeled the CCF of groups of equipment that were proposed for the change. In cases where the effects of the application on CCF cannot be easily evaluated or quantified, reviewers should establish that performance monitoring is capable of detecting CCF before multiple failures are likely to occur subsequent to an actual system challenge. In addition, to reduce fault exposure times for potential common cause failures, phased or incremental implementation should be considered as part of the effort to protect against CCF. • Reviewers should ensure that the impact of the change is not inappropriately made insignificant by the choice of CCF probabilities for SSCs unaffected by the change. This can occur in two ways. First, the cutsets or scenarios containing events that represent failures of SSCs affected by the change may include CCF contributions from other SSCs that are too small. Second, the contribution of cutsets or scenarios that do not contain affected SSCs may be artificially increased by having CCF contributions that are too large so that the impact of the change is obscured. These cases will impact applications involving risk categorization by lowering the relative