Document: NRC Regulatory Guide
Document ID: 2459a562-8984-421c-8058-d096dbb9617c
Document Type: regulatory_guide
Title: Guidelines for Categorizing Structures, Systems, and Components in Nuclear Power Plants According to Their Safety Significance
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0314/ML031430373.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.201
CFR Part: 
CFR Title: 

Content:
lated SSCs that perform low safety-significant functions. Finally, RISC-4 SSCs are non-safety-related SSCs that perform low safety-significant functions. The proposed amendment to 10 CFR 50.69 defines “safety-significant functions” as functions whose loss or degradation could have a significant adverse effect on defense in depth, safety margins, or risk. This definition was chosen to be consistent with the concepts described in Regulatory Guide 1.174 (ADAMS Accession No. ML003769599). The term used is “safety- significant” instead of “risk-significant” because the categorization process employed in 10 CFR 50.69 considers both probabilistic and deterministic information in the decision process. Through the process described in the industry guidance document discussed below, as modified by the staff positions, the RISC category for SSCs is determined. Functions that are not determined to be safety-significant are considered to be low safety-significant. 3 Figure 1. 10 CFR 50.69 RISC Categories 4 This Draft Regulatory Guide DG-1121 contains specific instructions and cautions in the use of the categorization process. The guidance is limited to that presented in the Regulatory Position of Draft Regulatory Guide DG-1121. This regulatory guide incorporates experience gained from a review of pilot programs, industry programs, and industry practices. C. REGULATORY POSITION This regulatory guide is being developed to provide guidance for determining whether an SSC performs safety-significant functions. 1. NRC Endorsement of Draft Revision C of NEI 00-04 Draft Revision C of NEI 00-04, “10 CFR 50.69 SSC Categorization Guidance,” dated June 28, 2002 (ADAMS Accession No. ML021910534), provides an approach that is acceptable to the NRC staff for meeting the categorization requirements in the proposed 10 CFR 50.69 (68 FR 26511), subject to the following clarifications, enhancements, and conditions. [To be determined upon resolution of the issues discussed in the