Document: NRC Regulatory Guide
Document ID: 47b09be1-4bf8-45f9-a099-7fed871c09bd
Document Type: regulatory_guide
Title: Plant-Specific, Risk-Informed Decisionmaking: Inservice Testing (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2114/ML21140A055.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.175
CFR Part: 
CFR Title: 

Content:
e “state of knowledge correlation effect” could be significant if there are a significant number of cut sets with similar SSCs contributing to the change in risk. RG 1.174 discusses the parametric uncertainty analysis in more detail. In addition, model and completeness uncertainties should be addressed as discussed in RG 1.174. In particular, initiating events and modes of plant operations whose risk impact are not included in the PRA need additional analyses or justification that the proposed changes do not significantly increase the risk from those nonmodeled contributors. 2.2.3.3.3 Acceptance Guidelines The change in risk from implementation of the proposed RI-IST program should be consistent with the guidelines discussed in Regulatory Positions C.2.4 and C.2.5 of RG 1.174. The licensee should address the model and completeness uncertainty, as discussed in Regulatory Position C.2.5 of RG 1.174. In addition, the licensee should address parameter uncertainty either by propagating the uncertainty during sequence quantification or by demonstrating that the “state-of-knowledge correlation” effect is not significant, especially in cut sets in which the proposed RI-IST program changes might affect multiple components that are similar. In evaluating the change in plant risk from the proposed changes from the RI-IST program, the licensee should perform the following: a. Evaluate the risk significance of extending the test interval on affected components. This requires that the licensee address the change in component availability as a function of test interval. The analysis should include either a quantitative consideration of the degradation of the component failure rate as a function of time, supported by appropriate data and analysis, or arguments that support the conclusion that no significant degradation will occur. RG 1.175, Page 18 b. Consider the effects of enhanced testing to the extent needed to substantiate the change. Other issues that should be