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:
process should yield well-defined estimates of CDF, LERF, and importance measures. The licensee should discuss and justify the threshold criteria used. As discussed in Section C.2.2.1, the consequence of segment failures may be represented by categories of consequences instead of quantitative estimates for each segment. In this case, the potential for pipe failure, as discussed in Section C.2.1.5, would also be developed as categories ranging from high to low, depending on the degradation mechanisms present and the corresponding likelihood that the segment will fail. These consequence and failure likelihood categories should be systematically combined to develop categories of safety significance. The licensee should discuss and justify how it relates the consequence and failure likelihood categories to the safety-significant category assigned to each combination. RG 1.178, Page 18 The safety-significance category of the piping segment will help determine the level of inspection effort devoted to the segment. In general, safety-significant segments will receive more inspections and more demanding inspections than low-safety-significant segments. In any integrated categorization process, the licensee needs to address the principles in RG 1.174. Irrespective of the method used in the analysis, the licensee should justify the final categorization process as being robust and reasonable with respect to the analysis uncertainties. 2.2.3 Demonstrate Change in Risk Resulting from Change in Inservice Inspection Program Any change in the ISI program has an associated risk impact. Evaluation of the change in risk may be a detailed calculation or it may be a bounding estimate supported by sensitivity studies, as appropriate. The change may be a risk increase, a risk decrease, or risk neutral. The change is evaluated and compared with the guidelines presented in RG 1.174. The staff expects that the RI-ISI program would lead to both risk reduction and reduction in radiation