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:
es; installation of oil-bath or enhanced air filters on diesel generators; and adjusting heating, ventilation, and air conditioning equipment. The actions would allow the Columbia plant to safely shut down in the event of a volcanic ash fall at the site from an eruption of a Cascade volcano. Mitigation of surface phenomena, such as lava flows or debris flows, appears more challenging than for volcanic ash falls. Some volcanic lava flows have been diverted successfully in past eruptions of Mount Etna in Italy, but not all attempts have been successful (Barberi et al., 1993, and 2003). In addition, successful diversion occurred in channelized terrain with moderate topographic gradients, which allowed for some control on the direction of flows. Successful mitigation of lava flows on relatively shallow topographic gradients has sometimes been proposed (e.g., Lockwood and Torgerson, 1980) but has not been implemented. A paucity of lava-flow diversion attempts reflects, in part, the legal complexities of diverting a flow into areas that likely would not have experienced a flow without diversion efforts. Mitigation actions that propose construction of diversionary structures against surface flows should provide the following: • a robust technical basis to determine the efficacy of proposed structures to divert surface flows, which often relies on numerical models that account for site-specific conditions (e.g., Crisci et al., 2010) • an examination of how similar diversionary structures have performed in past attempts to mitigate similar volcanic hazards • sufficient information to demonstrate the proposed construction is practicable in the time between initial alert levels and arrival of a surface flow at the site After the technical basis is established for determining the likelihood of successful mitigation of potential volcanic hazards, the volcanic hazards assessment should develop additional risk insights that consider the likelihood of successful mitigation.