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:
19, 1995) (Ref. 21), also discuss the use of probabilistic approaches to improve TS. Regulations on applications for and the issuance of license amendments appear in 10 CFR 50.90, 10 CFR 50.91, and 10 CFR 50.92. In addition, the licensee should DG-1287, Page 9 ensure that the evaluation identifies and considers any discrepancies between the proposed TS change and licensee commitments. 2.2 Deterministic Engineering Considerations 2.2.1 Technical Specification Change Is Consistent with Defense-in-Depth Philosophy (Principle 2) Defense in depth is an element of the NRC’s safety philosophy that employs multiple independent and redundant layers of defense to compensate for potential human and mechanical failures so that no single layer, no matter how robust, is exclusively relied upon. Defense in depth includes the use of access controls, physical barriers, redundant and diverse key safety functions, and emergency response measures to prevent accidents or mitigate damage if a malfunction, accident, or naturally caused event occurs at a nuclear facility. The defense-in-depth philosophy has traditionally been applied in plant design and operation to provide multiple means to accomplish safety functions and prevent the release of radioactive material. It has been and continues to be an effective way to account for uncertainties in equipment and human performance and, in particular, to account for the potential for unknown and unforeseen failure mechanisms or phenomena that, because they are unknown or unforeseen, are not reflected in either the PRA or deterministic engineering analyses. Staff Requirements Memorandum (SRM)-SECY-98-144, “Staff Requirements—SECY-98-144—White Paper on Risk-Informed and Performance-Based Regulation,” dated March 1, 1999 (Ref. 22), provides 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