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:
process that complements the peer review criteria with those of the American Society of Mechanical Engineers (ASME) PRA standard not addressed in NEI 00-02. The NRC staff expects the final version of NEI 00-04 to reference these documents as an appropriate way to ensure and document the acceptability of the underlying PRA for the purposes of categorization. Reference is made to the development and use of industry consensus standards on PRA, which is assumed by the NRC staff to be a reference to the development of a standard that is currently under way for external events PRA. As this standard is still under development and has not been formally reviewed and endorsed by the NRC, the statements in NEI 00-04 are not to be taken to be an endorsement of this standard by the NRC. The NRC staff notes that Draft Revision C of NEI 00-04 does not explicitly address modeling or data uncertainties. However, the sensitivity studies performed to support the categorization of SSCs using PRA models are intended to address the major sources of uncertainty identified (i.e., human error probabilities, common cause failure probabilities, and items identified during the assessment of PRA adequacy). When assessing the potential increase in CDF and LERF, uncertainties should be addressed as discussed in Section 2.2.5 of Regulatory Guide 1.174. The NRC staff also notes that there are potentially large differences in the levels of uncertainty in the modeling and data for the PRA models for the various types of events. This limits the ability of the licensee to perform the integral assessment proposed in Section 5.5 of Draft Revision C of NEI 00-04. It is for this reason that the NRC staff believes that it is appropriate to use the most conservative categorization over all the contributors taken individually. 6. Section 3.3 NEI 00-04 states that the Option 2 categorization process is a Grade-3 application per the NEI 00-02 peer review process. This can be demonstrated for the internal