Document: NUREG-0800
Document ID: e32f0820-4e33-476e-aa36-4ca8c2c64af0
Document Type: srp
Title: Use of Probabilistic Risk Assessment in Plant-Specific, Risk-Informed Decisionmaking:
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0119/ML011940192.pdf
Revision Date: 2023-06
Chapter: 19
Section ID: 19.0
CFR Part: 
CFR Title: 

Content:
an fail more than one component at the same time and can occur with greater probability than would be predicted by the product of the individual component failure probabilities, they can significantly contribute to plant risk. Risk-informed applicaticns that cover SSCs as a group have the potential to affect the CCF probabilities of SSCs witlin the given group. For the affected components, CCF probabilities could be low or might not even be included in the baseline PRA models based on the operational and engineering evidence driven by current requirements. With proposed changes, there should be assurance that the CCF contribution will not become more significant. In addition, the assessment of the impact of the change can be affected by the CCF probabilities for other components, and can either be exaggerated or obscured depending on the CCF probabilities. 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. Staff evaluation should include a review of the process used to select common cause component groups. Specific review guidelinE;s3 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 SRP 19-A14 system challenge.