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:
the PRA, but rather, the licensee should first examine and determine the cause of the high value and then revise the model, as necessary. 10. Section 5.2 It is the NRC staff’s interpretation of the discussion in the third paragraph of this section to mean that fire barriers would not be included within the scope of risk-informed treatment (i.e. would not be categorized) unless they are explicitly evaluated in the fire risk analyses. 11. Sections 5.2 and 5.3 NEI 00-04 recognizes in these sections that the vulnerability-type evaluation (e.g., FIVE) and margins-type analysis (e.g., seismic margins analysis) are somewhat limited in being able to support the identification of LSS SSCs. It is further stated that the approach for these types of analyses is conservative since SSCs are determined to be safety-significant essentially if they are identified in these analyses. For the FIVE analysis, SSCs are safety-significant if they participate in the scenario or are credited in the screening of the scenario. For the seismic margins analysis, SSCs are safety-significant if they are credited in the safe shutdown path. The licensees, as part of their submittal to the NRC requesting to implement 10 CFR 50.69, must demonstrate the adequacy of these types of analyses for this application and ensure that they will provide conservative results. If a licensee wants to gain the full benefit from the proposed 10 CFR 50.69 in reducing treatment of SSCs, the licensee should consider performing a fire and/or seismic PRA, which would provide greater ability to identify SSCs that could potentially be categorized as LSS. 12. Section 5.4 As the evaluation of other external events typically is a screening approach, NRC believes that a logic similar to Figure 5-4 might be more appropriate than the current Figure 5-6. Thus, if a SSC participates in an unscreened scenario or is credited in the screening of the scenario, then that SSC would be considered safety-significant. 13. Section 5.5