Document: NRC Regulatory Guide
Document ID: 46b2c829-ce4c-4a6a-8a01-908725558ffe
Document Type: regulatory_guide
Title: Volcanic Hazards Assessment for Proposed Nuclear Power Reactor Sites + HISTORY - HISTORY 03/2020 – DG-4028-Proposed New Guide
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML2000/ML20007D621.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.26
CFR Part: 
CFR Title: 

Content:
.g., Volume 60 of the Federal Register, page 42622 [60 FR 42622]). The NRC established the use of the Senior Seismic Hazards Analysis Committee (SSHAC) process as an acceptable method to account for a wide range of uncertainties in the analysis of natural hazards and other technical subjects. The NRC published the most recent guidelines in NUREG-2213, “Updated Implementation Guidelines for SSHAC Hazard Studies,” issued October 2018 (NRC, 2018). The SSHAC process (or its equivalent) has been used successfully to evaluate seismic and volcanic hazards at a variety of sites worldwide, as described more fully in NUREG-2117, “Practical Implementation Guidelines for SSHAC Level 3 and 4 Hazard Studies,” issued April 2012 (NRC, 2012). A SSHAC study can be accomplished at four levels that increase in complexity and cost and that result in corresponding increases in regulatory assurance. Selection of the appropriate study level is subjective and considers many qualitative factors, such as the level of public concern about the proposed facility and the scope of regulatory requirements. Nevertheless, the NRC staff provides the following guidance on selecting the SSHAC study level to support a volcanic hazards assessment: DG-4028, Page 9 • Level 1: facility with low-level source terms or design fragilities, modest number of alternative hazard models available, high confidence in the completeness and accuracy of the geologic record, and several straightforward hazard scenarios considered • Level 2: facility with intermediate source terms or design fragilities, modest number of alternative hazard models available; moderate confidence in the completeness and accuracy of the geologic record, and multiple hazard scenarios considered • Level 3: facility with potentially large source terms or design fragilities; potentially significant number of alternative hazard models available; moderate-to-low confidence in the completeness and accuracy of the geologic record; and