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: 

Content:
vents (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 safety-related (SR) SSCs are available to mitigate the events. NEI 18-04 includes definitions and demarcations of the event categories in Table 3.1, “Definitions of Licensing Basis Events,” and Figure 3.1, “Frequency- Consequence [F-C] Target.” The methodology includes plotting event sequence families on the F-C target and assessing margins based on event frequency and estimated 30-day dose at the exclusion area boundary. The mean values of the frequencies are used to classify the LBEs into AOOs, DBEs, and BDBE categories. However, as described in NEI 18-04 Section 3.2.2, “LBE Selection Process,” when the uncertainty bands defined by the 5th percentile and 95th percentile of the frequency estimates straddles a frequency boundary, the LBE is evaluated in both LBE categories. NEI 18-04 acknowledges that the F-C target does not correspond to actual regulatory acceptance criteria but is instead a vehicle to assess a range of events to determine risk significance, support SSC classification, determine special treatment requirements, identify appropriate programmatic controls, and confirm the adequacy of DID. 4 The statements in this draft RG about the proposed acceptability of the methodology described in NEI 18-04 are subject to change as a result of interactions with stakeholders and the resolution of public comments. The NRC staff also plans to provide a paper to the Commission requesting its review and approval of the overall approach described in NEI 18-04. Draft Revision N of NEI 18-04 is available under ADAMS Accession No. ML18271A172. Interactions with stakeholders and the Commission’s directions related to the Commission paper will be reflected in the final RG. 5 The definitions of some phrases used in NEI 18-04 are different from the same phrases