Document: NRC Regulatory Guide
Document ID: c7a40fcc-fc9d-4eb2-ad86-f9f5b0f04c82
Document Type: regulatory_guide
Title: Plant-Specific, Risk-Informed Decisionmaking:  Technical Specifications (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1920/ML19206A489.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.177
CFR Part: 
CFR Title: 

Content:
and Regulatory Positions C.2.3.6 and C.2.3.7 outline issues associated with Tier 2 and Tier 3, respectively. The NRC staff has identified several factors, discussed below, that should be considered in proposals for SF changes. In summary, the licensee should identify the SFs to be evaluated, determine the risk contribution associated with the subject SFs, determine the risk impact from the change to the proposed SF, and perform sensitivity and uncertainty evaluations to address uncertainties associated with the SF evaluations. Regulatory Positions C.2.3.1–2.3.6 and Appendix A to this RG provide more detail on risk evaluation for SF changes. 2.3.1 Acceptability of the Probabilistic Risk Assessment The PRA used to support the TS change evaluation 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 are to be commensurate with its intended use and the role the PRA results play in justifying the TS change. This applies to Tier 1 and to Tiers 2 and 3 to the extent that a PRA model is used. Regulatory Position C.2.3 of RG 1.174 provides guidance on evaluating the acceptability of the PRA with respect to these PRA aspects and should be applied to evaluate the acceptability of the PRA used to support TS change evaluations. In addition, Regulatory Positions C.2.3.2 and C.2.3.3 of this RG provide additional guidance on assessing the acceptability of the PRA scope and PRA level of detail, respectively, for TS change evaluations. 2.3.2 Scope of the Probabilistic Risk Assessment for Technical Specification Change Evaluations The scope necessary to fully support the evaluation of a TS change depends on the type of TS change being sought. The scope required is discussed below for a variety of cases. However, in some cases, a PRA of sufficient scope may not be available. This will have to be compensated for by qualitative arguments, bounding analyses, or