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:
nic hazards assessments that would be relevant to applications for proposed new reactors. The NRC staff is aware of and has staff participants in an American Nuclear Society working group to develop a standard related to volcanic hazards. This standard is not yet available and therefore not considered further in this draft guide. DG-4028, Page 11 C. STAFF REGULATORY GUIDANCE The Volcanic Hazards Assessment For new reactors, the NRC staff determined the approach given below is acceptable for conducting a volcanic hazards assessment to meet applicable regulatory requirements. The information and associated uncertainties considered in the following steps can be evaluated acceptably through the SSHAC process (NRC, 2018). Figure 1 of this guide illustrates the sequential steps of a risk-informed approach for conducting volcanic hazards assessments to support license applications for new reactors. As shown in Figure 1, the outcome of each step may result in the completion of the volcanic hazards assessment. Subsequent steps should be conducted as needed. Figure 1 Flowchart for an acceptable volcanic hazards assessment. (“Y” = Yes, “N” = No, “U” = Unacceptable performance, A = “Acceptable performance) DG-4028, Page 12 Step 1: Perform Initial Characterization The volcanic hazards assessment should consider the Quaternary Period, defined as the geologic timeframe ranging from 2.6 million years ago to the present, to provide sufficient margin to the historical period to accurately evaluate the timing and character of infrequent geologic events such as volcanic eruptions. The volcanic hazards assessment should consider a radius of at least 320 km (200 mi), extending in all directions from a proposed facility, as the appropriate region of interest for initial characterization of volcanic hazards other than ash fall, consistent with NUREG-0800, Section 2.5.1. Ash-fall hazards can occur from volcanoes located farther than 320 km (200 mi) from a site. For the purpose