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:
ions. After consideration of the appropriate uncertainties, a volcanic hazard can be screened from further consideration in the volcanic hazards assessment if the site is located more than the maximum distance the hazardous phenomena can extend from the source vent. Only those volcanic hazards that could potentially extend to the proposed site (i.e., screens in) need to be evaluated in the next steps of the volcanic hazards assessment. If a proposed site is located beyond the maximum distance for all credible volcanic hazards from all potential source volcanoes in the region of interest (i.e., screens out), then no further volcanic hazards assessment is warranted. Step 3: Develop Initial Risk Insights For potential hazards that are included in the volcanic hazards assessment after Step 2 screening, initial risk insights can be developed with a simplified analysis that assumes the occurrence of these volcanic hazards would represent a beyond-design-basis event. Thus, the PRA could assume the probability of SSC failure (i.e., unacceptable performance) is 100 percent. Using these assumptions, the PRA results could be evaluated to determine whether the total system performance would be acceptable for volcanically induced failure of the SSCs. This evaluation would necessarily include the suite of considerations used to make risk-informed regulatory decisions (e.g., SECY-98-144). If these initial risk insights determined that volcanically induced failure of SSCs resulted in acceptable performance, then no further volcanic hazards assessment would be warranted. However, if performance is viewed as unacceptable, or there are other risk insights that warrant consideration, then the volcanic hazards assessment would proceed to Step 4. Step 4: Evaluate Eruption Potential and/or Hazard Potential A traditional volcanic hazards assessment would first calculate the probability of a future volcanic eruption occurring (PE), then calculate the conditional likelihoods of potentially