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:
eviations (if any) have been justified on the basis of plant-specific factors. • The licensee has systematically considered the possibility that individual components could be performing more poorly than the average associated with their class, and has avoided relaxation for those components to the point where the unavailability of the poor performers would be appreciably worse than that assumed in the risk analysis. • The changes to the parameter values impacted by the application are both justified and reasonable. • Data used to support changes to the plant's design or operations are supported by an appropriate performance monitoring program. A.7 Modeling of Common Cause Failures a. Areas of Review Common cause failures (CCFs) represent the failures of components that are caused by common influences such as design, manufacturing, installation, calibration, or operational 19.2-53 June 2007 deficiencies. Since CCFs can 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 applications that cover SSCs as a group have the potential to affect the CCF probabilities of SSCs within 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