Document: NRC Regulatory Guide
Document ID: 6f84e3bf-9ff3-49fb-a16a-0de3b89e6bc6
Document Type: regulatory_guide
Title: An Approach for Plant-Specific Risk-Informed Decisionmaking for Inservice Inspection of Piping (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2103/ML21036A105.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.178
CFR Part: 
CFR Title: 

Content:
isk metrics, respectively. NRC safety evaluation dated January 18, 2012, “Final Safety Evaluation of Electric Power Research Institute Topical Report, 1021467, Revision 0, Nondestructive Evaluation: Probabilistic Risk Assessment Technical Adequacy Guidance for Risk-Informed In-Service Inspection Programs” (Ref. 30), endorses EPRI TR-1021467-A, RG 1.178, Page 16 “Nondestructive Evaluation: Probabilistic Risk Assessment Technical Adequacy Guidance for Risk- Informed Inservice Inspection Programs” (Ref. 31). This topical report is based on RG 1.200 and provides guidance on determining the technical acceptability of PRAs used to develop a RI-ISI program and identifies the specific supporting requirements of the PRA standard that are applicable to RI-ISI programs. While a full-scope PRA that covers all modes of operation and initiating events is preferred, a lesser scope PRA can be used to provide useful risk information. However, it should then be supplemented by additional considerations, as discussed below. 2.2.1 Modeling Piping Failures in a Probabilistic Risk Assessment Input from the deterministic engineering analysis addressed in Section C.2.1 includes the identification of piping segments from the point of view of the failure potential (degradation mechanisms) and consequences (resulting failure modes and consequential primary and secondary effects). The deterministic analysis identifies both the primary and secondary effects that can result from a piping failure. The assessment of the primary and secondary failures identifies the portions of the PRA that are affected by the piping failure. Each piping segment failure may have one of three types of impacts on the plant: a. Initiating event failures occur when the failure directly causes a transient and may or may not also fail one or more plant trains or systems. b. Standby failures are those failures that cause the loss of a train or system but that do not directly cause a transient. Standby failures are