Document: NUREG-0800
Document ID: 4e1d86bd-74a5-4678-8bc0-ffce3ba28ea0
Document Type: srp
Title: RISK-INFORMED INSERVICE TESTING
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0428/ML042880272.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.7
CFR Part: 
CFR Title: 

Content:
ime other than this: a different fault exposure time for a given component might be claimed as a result of credit taken for non-IST validation of the performance of the component, perhaps by virtue of system challenges, or an IST test on a different component that implicitly requires functioning of the subject component and would therefore reveal a failed state of the subject component. The reviewer should establish that the licensee has identified a basis for fault exposure times modeled, and that commitments are in place wherever a fault exposure time is determined by a programmatic activity. Where a fault exposure time is the result of tests on other components, the reviewer should verify that there is assurance that these other tests will be performed and that the behavior of the subject component will be surveilled in the course of these tests. Where a fault exposure time is the result of system challenges, the reviewer should verify that this challenge frequency is consistent with system challenge frequencies modeled elsewhere in the PRA. Evaluation of Change in Risk The comparison of the quantitative results of the PRA with the regulatory positions contained in acceptance guidelines of Regulatory Guide 1.174 provides input to the demonstration that, if increases in risk are proposed, these increases are small and consistent with the intent of the 3.9.7-20 Rev. 0 -August 1998 Commission's Safety Goal Policy Statement. General guidance on the evaluation of the change in risk is given in Section 111.2.2 and Appendix A of SRP Chapter 19. Some issues specific to the IST evaluation are given below. Initiating Events: The reviewer is not expected to independently verify the licensee's evaluation of the effect of [ST program changes on initiating event frequency. Rather, the reviewer is expected to look for evidence that the licensee has considered the effects of IST changes on initiating events that were analyzed in the PRA and those that were previously screened