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:
s 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 events PRA, as described in NEI 00-02, as amended to incorporate NRC comments provided in the NRC letter to NEI dated April 2, 2002. Therefore, the licensee must provide sufficient justification for the adequacy of their PRA for this application and must address any technical elements that do not meet the required grade for this application (i.e., receive a grade of 1 or 2 on individual technical elements) and the significant peer review Facts and Observations (i.e., Categories A or B). Further, the NRC believes that a higher grade for PRA quality cannot be achieved by sensitivity studies, though sensitivity studies can be used to explore the impacts of modeling uncertainties on the categorization. The NRC staff notes that these sensitivity studies must also be evaluated in the “Component Safety Significance Assessment” step (Chapter 5) as the additional applicable sensitivity studies identified in the characterization of PRA adequacy in Tables 5-2, 5-3, 5-4, and 5-5. In addition to demonstrating that the internal events PRA input to fire, seismic, and shutdown PRAs is technically acceptable, it is also necessary to demonstrate the technical acceptability of those elements dealing with the initiating event and specific mitigating features (e.g., initiating event frequencies, fire detection and suppression systems, etc.). Since no NRC-endorsed standards exist for these elements, the licensee must describe the licensee’s approach and justify its acceptability for these elements. 4 NEI 00-04 does not identify the need for licensees to address the adequacy of any non-PRA types of analyses, such as a margins-type study, used in the categorization process. The licensees must explicitly address and document in their plant-specific submittal to the NRC, the adequacy of