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:
hat support an RG 1.175, Page 13 application, is sufficient to provide confidence in the results, such that the PRA can be used in regulatory decisionmaking for LWRs. In an RI-IST program, information obtained from a PRA should be used in two ways: (1) to provide input to the categorization of SSCs into HSSC groupings, and (2) to assess the impact of the proposed RI-IST program on CDF and LERF. Regulatory Position C.2.2.3.1 discusses, in general terms, issues related to the scope, level of detail, conformance with the technical elements of the ASME/ANS PRA standard, and plant representation of a PRA that is used for RI-IST applications. Regulatory Positions C.2.2.3.2 and C.2.2.3.3 give more specific considerations and address the use of PRA in categorization and in the assessment of the impact on risk metrics, respectively. 2.2.3.1 Acceptability of Probabilistic Risk Assessments for Inservice Testing Applications For the quantitative results of the PRA to play a major and direct role in decisionmaking, such results should be derived from “acceptable” analyses, and the extent to which the results apply should be well understood. Both Regulatory Position C of RG 1.200 and the Regulatory Position C.2.3 of RG 1.174 address, in general terms, acceptability of the PRA. The PRA analysis used to support an application is measured in terms of its appropriateness with respect to scope, level of detail, conformance with the technical elements, and plant representation. These aspects of the PRA should be commensurate with its intended use and the role the PRA results play in the integrated decision process. While a full-scope PRA that covers all modes of operation and initiating events is preferred, a lesser scope PRA can provide useful risk information. If less than a full-scope PRA is used to support the proposed RI-IST program, supplemental information (deterministic and qualitative) should be considered during the integrated decisionmaking process. Regulatory Position