Document: NRC Regulatory Guide
Document ID: 82659041-98b0-4721-b25d-c4fb2ea394d0
Document Type: regulatory_guide
Title: An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1635/ML16358A153.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.174
CFR Part: 
CFR Title: 

Content:
as involving the categorization of SSCs according to safety significance. An example is grading the application of special treatment requirements commensurate with the safety significance of equipment under 10 CFR 50.69, “Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Plants” (Ref. 26). Related to other applications, the staff’s review of licensing basis change requests for applications involving safety categorization should be in accordance with the acceptance guidelines associated with each key principle presented in this RG, unless the licensee proposes alternative, equivalent guidelines. Since risk-importance measures are often used in such categorizations, Appendix A to this RG provides guidance on their use. Other application-specific guidance documents address guidelines associated with the adequacy of programs (in this example, special treatment requirements) implemented for different safety-significant categories (e.g., more safety significant and less safety significant). Licensees are encouraged to apply risk-informed findings and insights to decisions (and potential licensing basis requests). As part of Element 2, the licensee should evaluate the proposed licensing basis change with regard to the principles of maintaining consistency with the defense-in-depth philosophy, maintaining sufficient safety margins, and ensuring that proposed increases in CFR and LERF are small and are consistent with the intent of the Commission’s Safety Goal Policy Statement. 2.1 Evaluation of Defense-in-Depth and Safety Margins One aspect of the engineering evaluation is to show that the proposed licensing basis change does not compromise the fundamental safety principles on which the plant design and operation (i.e., activities such as maintenance, testing, inspection, and qualification) was based. During the design process, plant response and associated safety margins are evaluated using assumptions of physical