Document: NRC Regulatory Guide
Document ID: 4f130c35-25dc-4950-b437-3801efdab5f6
Document Type: regulatory_guide
Title: Protection Against Extreme Wind Events and Missiles for Nuclear Power Plants (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1435/ML14356A107.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.117
CFR Part: 
CFR Title: 

Content:
so be designed to withstand the effects of the design-basis hurricane and hurricane-generated missiles and remain functional, as defined in RG 1.221. In addition, the guide has been updated to use the term, “extreme winds,” which encompasses both tornado and hurricane winds and better reflects the purpose of the guidance. Background Nuclear power plants should be protected from the effects of extreme winds and wind-generated missile strikes. The likelihood of a credible tornado or hurricane strike varies from about 10-7 per year to values several orders of magnitude higher. Physical design parameters of tornado and hurricane protection provisions are such that designated structures, systems, and components will be able to maintain their necessary capabilities in the event of a design basis tornado or hurricane, as defined in RG 1.76 and RG 1.221 respectively. This DG-1313, Page 3 ensures that protection of the designated items against all credible extreme wind events has been adequately considered. A basic provision of extreme wind protection criteria is that those structures, systems, and components whose failure could result in conservatively calculated exposures comparable to the guideline exposures of 10 CFR Part 100, “Reactor Site Criteria,” should be protected against design-basis tornado or hurricane effects to prevent such failure. This provision by itself, however, would not provide protection for certain other structures, systems, and components that could be damaged by a less severe, but more likely, extreme wind events. To ensure protection for more probable events having less severe consequences, the selection of structures, systems, and components to be protected against the effects of a design-basis tornado and hurricane is based on not allowing offsite exposures to exceed an appropriate fraction of 10 CFR Part 100 guidelines. Protection of designated structures, systems, and components may generally be accomplished by designing protective