Document: NUREG-0800
Document ID: b07c8dd1-23f6-41f1-a3ba-aa378f9ea59a
Document Type: srp
Title: RISK-INFORMED INSERVICE INSPECTION
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0325/ML032510135.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.8
CFR Part: 
CFR Title: 

Content:
the impact of the proposed change in the ISI program is based on the adequacy of the traditional engineering analysis, acceptable change in plant risk relative to the criteria, and the adequacy of the proposed implementation and performance monitoring plan. The intent of the ASME B&PVC to maintain integrity of reactor coolant system boundary by ISI should be preserved under the RI-ISI program. An acceptable approach for the risk ranking of piping segments and elements is the use of risk reduction worth (RRW), risk achievement worth (RAW), conditional core damage probability (CCDP), conditional large early release probability (CLERP), or other importance measures. RRW is a measure of the maximum possible reduction in total CDF or LERF due to pressure boundary failures in plant piping systems that can result from making a component perfectly reliable. RAW, CLERP, and CCDP characterize the increase in risk associated with the pressure boundary failure. The risk ranking methodology must be able to systematically identify all safety- significant pipe segments within the scope of the RI-ISI program. Guidelines for using risk importance measures to categorize SSCs with respect to safety significance can be found in Appendix A, “Use Of Risk-Importance Measures To Categorize Structures, Systems, and Components with Respect to Safety Significance,” to Regulatory Guide 1.174. The classification of piping segments should be evaluated to determine whether any piping segment is inappropriately classified. Consideration should be given to the limitations resulting from the PRA structure, PRA scope, and risk-importance measures. Operational insights from previous inspection results, industry data on pipe failures, and Maintenance Rule impacts should also be taken into account. Piping that is subject to ISI under ASME B&PVC Section XI requirements but has no segments exceeding the piping segment screening criteria should be further reviewed. Each ASME Class coded system should