Document: NRC Regulatory Guide
Document ID: b3da4d67-03d8-4f52-b04b-8e76d142c857
Document Type: regulatory_guide
Title: Guidance for a Technology-Inclusive, Risk-Informed, and Performance-Based Methodology to Inform the Licensing Basis and Content of Applications for Licenses, Certifications, and Approvals for Non-Light Water Reactors + HISTORY - HISTORY 05/2019 – Issued DG-1353 , Proposed Revision 0
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1831/ML18312A242.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.233
CFR Part: 
CFR Title: 

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informing the licensing basis and content of applications for permits, licenses, certifications, and approvals for non-LWRs.4 The staff takes no significant exceptions to the guidance in NEI 18-04 but does provide clarifications and points of emphasis as detailed in this RG. One key distinction between NEI 18-04 and current NRC guidance and regulations developed for LWRs is that the definition of “safety related” SSCs in NEI 18-04 is different from the NRC’s definition of “safety-related” SSCs in 10 CFR 50.2. The NRC staff has determined that the methods described in NEI 18-04 constitute one acceptable means to identify LBEs, classify SSCs, establish special treatments, identify programmatic controls, and assess DID for non-LWRs. As described below, these activities also define a methodology for applicants to identify and provide the appropriate level of information needed to satisfy parts of the regulatory requirements in 10 CFR 50.34, 10 CFR 52.47, 10 CFR 52.79, 10 CFR 52.137, and 10 CFR 52.157. Each section in NEI 18-04 summarized below is part of an integrated methodology that includes defined relationships among LBEs, equipment classification, special treatments, programmatic controls, and assessments of DID. The applicants perform the evaluations in an iterative fashion as they develop the design and licensing strategies. 1. Selection of Licensing-Basis Events An important part of the design process for reactor designs is the identification of events that could challenge key safety functions and layers of defense against the release of radioactive materials. NEI 18-04 describes a systematic process for identifying and categorizing event sequences as anticipated operational occurrences (AOOs), design-basis events (DBEs), or beyond-design-basis events (BDBEs) for non-LWRs.5 The primary determinate for categorizing events is the estimated frequency of the event sequence. Design-basis accidents (DBAs) are derived from DBEs by assuming that only