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:
hen it is endorsed by the NRC staff. The NRC endorsement of this ASME standard is currently under development and will be published as a regulatory guide. These documents cover internal events at full power only. Draft Revision C of NEI 00-04 does not address the application- specific quality/adequacy required of the external events PRA and non-PRA type analyses (e.g., FIVE, seismic margins analysis, NUMARC 91-06) and there is no industry guidance for determining the quality or adequacy attributes required for these types of analyses for this specific application. Industry standards are being prepared for external events (seismic, high winds, and other external events), fire, and low power and shutdown PRAs, although with the exception of the external events standard, they are not expected to be completed in the near future. Therefore, the NRC staff expects that the applicant will prepare arguments for why the method employed is adequate to perform the analysis required to support the categorization of SSCs. Until such time that these standards are available, these arguments supporting the quality and adequacy of the external events and non-PRA type analyses for each plant-specific submittal requesting to implement 10 CFR 50.69 will have to be evaluated on a case-by-case basis. 7. Uncertainty Considerations in Draft Revision C of NEI 00-04 The NRC staff notes that Draft Revision C of NEI 00-04 does not address modeling or data uncertainties explicitly. However, the sensitivity studies performed to support the categorization of SSCs using PRA models are intended to address the major identified sources of uncertainty (i.e., human error probabilities, common cause failure probabilities, and items identified during the assessment of PRA adequacy). When assessing the potential increase in core damage frequency (CDF) and large early release frequency (LERF), uncertainties should be addressed as discussed in Section 2.2.5 of Regulatory Guide 1.174. The NRC staff also notes