Document: NRC Regulatory Guide
Document ID: db0c5d18-2d27-4720-8935-40b402e52f9a
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:
le, and as complete as the current stage of design permits. The subsequent use of the PRA by the designer is used to develop or confirm the events, safety functions, key SSCs, and adequacy of DID; and provides a structured framework to risk-inform the application for the specific reactor design. The designer’s quantification of frequencies and consequences of event sequences in the PRA, and the associated quantification of uncertainties, provides an objective means of comparing the likelihood and consequence of different scenarios in relation to the F-C target. The scope of the PRA, when completed, should cover internal and external hazards and provide an estimate of radiological consequences when the design is completed and site characteristics are defined. Designers seeking certifications or approvals prior to site selection may make assumptions related to site characteristics and external hazards, which would be confirmed or adjusted for licensing an advanced non-LWR at a specific site. Figure 3-2, “Process for Selecting and Evaluating Licensing Basis Events,” in NEI 18-04 depicts the iterative process needed to identify and evaluate LBEs and reflects that PRA models are expected to be developed by the designer and refined as the design process progresses and the licensing-basis documents are developed.6 NEI 18-04 acknowledges that reactor designers may propose to address all or parts of the process by assessing layers of defense, including physical barriers, and showing that the facility can contain radioactive materials with a high degree of confidence. Such an approach would still require a designer to obtain some of the information from a PRA, including the identification of challenges to the physical barriers and identification and evaluation of dependencies among the physical barriers. The PRA complexity should reflect the as-designed reactor plant, which, in turn, may incorporate the simple systems, inherent safety characteristics, and limited public