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:
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 compensatory measures. At a minimum, evaluations of CDF and LERF should be performed to support any risk-informed changes to TS. The scope of the analysis should include all hazard groups (i.e., internal events, internal flood, internal fires, seismic events, high winds, transportation events, and other external hazards) unless the contribution from specific hazard groups does not affect the decision. When the risk associated with a DG-1287, Page 12 particular hazard group or operating mode would affect the decision being made, the Commission’s policy is to assess the risk using a staff-endorsed PRA standard for that hazard group or operating mode. Regulatory Positions C.2.3.1 and C.2.5 of RG 1.174 provide more detail. When changes to the requirements for systems needed for decay heat removal are considered, an appropriate assessment of shutdown risk should also be considered. Examples of such systems are auxiliary feedwater, residual heat removal, emergency diesel generator, and service water. In addition, when CTs are being modified to facilitate online maintenance (i.e., transferring scheduled preventive maintenance from shutdown to power operation), the impact on the shutdown modes should also be considered. Using both power operation and shutdown models, when available, a comparative evaluation may be presented to decide the appropriate condition for scheduling maintenance based on risk evaluations. In some cases, a semiquantitative analysis of shutdown risk may be adequate (e.g., fault tree analysis or failure modes and effects analysis). When CTs are being modified in anticipation of the need for additional time for corrective maintenance, an assessment of transition risk (the risk of transitioning from power operation to the mode required by the current TS in