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:
t of radioactive waste arising from nuclear fuel cycle facilities; and nuclear fuel cycle related research and development facilities. DG-4028, Page 5 • Ash Fall: Many volcanic eruptions eject large volumes of pulverized rock into the atmosphere, which can travel tens to hundreds of kilometers from the source volcano. The pulverized rock fragments can be very small (0.001–2 millimeters [mm], 4×10-5–0.08 inch [in]) and are relatively hard (e.g., comparable to hardened metal alloys). During an eruption and for some time afterwards, airborne concentrations of volcanic ash can range from less than 0.01 to approximately 1 gram per cubic meter (g/m3) (less than 10-5–0.001 ounce per ft3). Deposits of volcanic ash can impart physical loads on the order of 100–1,000 kilograms per square meter (kg/m2) (6.2–62 pounds per square foot [ft2]) when dry, which can double when wet. When dampened (e.g., by fog or light rain), volcanic ash can be sufficiently conductive to create significant arcing across electrical insulators. Because volcanic ash is transported by atmospheric winds, initial arrival of ash at a site might occur hours after the onset of an eruption at a distant volcano. The design basis of the Columbia NPP, and NPPs elsewhere around the world, considered volcanic ash falls. • Opening of a New Vent: The formation of a new volcanic vent directly disrupts an area of about 1 square kilometer (247 acres) and can include significant ground deformation (on the order of meters of displacement) and the expulsion of meter-sized blocks up to several kilometers away from the vent. In addition, lava flows often erupt from the newly formed vent and typically can travel 1 km (0.6 mi) or more a day. Precursory earthquake activity may occur for several weeks before a new vent forms, although some new vents have formed within a day of earthquakes being felt in the vent area. IAEA SSG-21 concluded that the opening of a new volcanic vent within approximately 1 km (0.6 mi)