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:
f past events. In these situations, maximum-extent estimates might be developed from information in appropriate analogue volcanic systems or from general information in, for example, IAEA-TECDOC-1795. The rationale for using alternative sources of information should be thoroughly documented. After establishing the maximum distance that potential hazards can extend from the source(s), the screening analysis should evaluate whether the proposed site is located within or beyond the reach of each DG-4028, Page 14 hazard. This analysis must consider whether the locations of future eruption sources have been appropriately evaluated. For many distributed volcanic fields (e.g., eastern Snake River Plain), future vent locations are not known and can only be estimated based on interpretations of past patterns of activity. In addition, many central vent volcanoes can erupt from vents on the flanks, or beyond the base, of the volcano (e.g., Sherrod et al., 1997). Consequently, the screening analysis needs to consider uncertainties in the location of future vents. In addition to uncertainties in vent locations, the screening analysis also should consider whether past characteristics in topography or atmospheric wind conditions appropriately represent future characteristics. Changes in surface topography through time can strongly affect the direction and extent of surface flows, and the screening analysis should consider whether uncertainties in the maximum distance should be adjusted to account for the potential effects of an evolving topography between the source vent and the site. Similarly, analyses of ash-fall hazards should consider if atmospheric conditions that controlled the distribution of the largest past events are appropriate representations of potential future conditions. 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