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:
ars) as providing sufficient margin to the historical period to accurately evaluate the timing and character of past geological events (e.g., NUREG-0800, Section 2.5.1). The duration of the Quaternary Period provides sufficient confidence that low-likelihood events have been captured in the geologic record, such that projections of future events can be reasonably based on this record. Rationale for the Regions of Interest For the purpose of the initial evaluation of potential hazards from volcanic phenomena other than ash falls, the region of interest extends 320 km (200 mi) from the proposed site. In the staff’s view, evidence of past volcanic activity within the region of interest during the Quaternary Period indicates a potential for future volcanic activity, which represents the need to conduct further investigations of the DG-4028, Page 7 potential for volcanic hazards at the proposed site. This distance encompasses typical screening distances for many potential volcanic hazards (e.g., IAEA-TECDOC-1795). This region of interest is consistent with previous NRC guidance related to site investigations, particularly the region investigated for other geological features and potential geologic hazards (i.e., NUREG-0800, Section 2.5.1). NUREG-0800, Section 2.5.1, states that “[i]n some locations, for example, the potential for very large earthquakes or for volcanic activity might require investigations to be performed at greater distances from the site than 320 km (200 mi).” For the purposes of the initial evaluation of potential hazards from volcanic ash falls, the NRC staff has determined that the region of interest should extend a sufficient distance to encompass those Quaternary volcanic systems with the potential to exceed the design basis of the proposed reactor’s SSCs. In practice, the NRC staff notes that, in accordance with IAEA-TECDOC- 1795, volcanic ash-fall hazards may necessitate extending the region of consideration 500–1,000 km (310–620 mi)