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:
rovides additional information on defense in depth as an element of the NRC’s safety philosophy. The engineering evaluation should demonstrate whether the implementation of the proposed TS change is consistent with the defense-in-depth philosophy (Principle 2 in RG 1.174). The intent of this key principle of risk-informed decisionmaking is to ensure that the licensee fully understands, and the submittal addresses any impact of the proposed licensing basis change on defense in depth and that the change maintains consistency with the defense-in-depth philosophy. The intent is not to prevent changes in the way defense in depth is achieved. The licensee should fully understand how the proposed licensing basis change impacts plant design and operation from both risk and deterministic engineering perspectives. RG 1.174 provides guidance on how to evaluate the impact of a proposed licensing basis change on defense in depth to determine whether that consistency is achieved. The seven defense-in-depth considerations in Section C.2.1.1 of RG 1.174 should be used to evaluate the impact of a proposed TS change on defense in depth to determine whether it maintains consistency with the defense-in-depth philosophy. Additionally, the licensee should select engineering analysis techniques—whether quantitative or qualitative, deterministic or probabilistic—appropriate for the proposed TS change, that address: a. whether there are appropriate restrictions in place to preclude simultaneous equipment outages that would erode the principles of redundancy and diversity, b. whether compensatory measures that should be taken when entering the modified CT for preplanned maintenance are identified, c. whether voluntary removal of equipment from service during plant operation is scheduled when adverse weather conditions are predicted, or when the plant may be subjected to other abnormal conditions, and DG-1287, Page 10 d. whether the impact of the TS change on the safety function should