Document: NRC Regulatory Guide
Document ID: ee571544-47f4-47c8-b15f-c0f8619885f5
Document Type: regulatory_guide
Title: Design-Basis Hurricane and Hurricane Missiles for Nuclear Power Plants + HISTORY - HISTORY 08/2012 – DG-1247 ,Proposed Revision 0
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1004/ML100480890.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.221
CFR Part: 
CFR Title: 

Content:
based on missile aerodynamic and initial condition assumptions that are similar to those used for the analyses of tornado-borne missile velocities adopted for Revision 1 of RG 1.76. In particular, no dependence of missile drag coefficient on missile position or relative missile speed with respect to the windflow was considered. However, the assumed hurricane wind field differs from the assumed tornado wind field in that the hurricane wind field does not change spatially during the missile’s flight time but does vary with height above ground. Because the size of the hurricane zone with the highest winds is large relative to the size of the missile trajectory, the hurricane missile is subjected to the highest windspeeds throughout its trajectory. In contrast, the tornado wind field is smaller, so the tornado missile is subject to the strongest winds only at the beginning of its flight. This results in the same missile having a higher maximum velocity in a hurricane wind field than in a tornado wind field with the same maximum (3-second gust) windspeed. C. REGULATORY POSITION The NRC staff has established the following regulatory positions for use in selecting the design- basis hurricane windspeed and hurricane-generated missiles that a new nuclear power plant should be designed to withstand to prevent undue risk to the health and safety of the public. 1. Design-Basis Hurricane Windspeeds Windspeeds specified in Figures 1, 2, and 3 for the appropriate regions identified are acceptable to the NRC staff for defining the design-basis hurricane for a new nuclear power plant. If a design-basis hurricane proposed for a given site is characterized by parameter values less conservative than the values presented in Figures 1 through 3, a comprehensive analysis should be provided to justify the selection of the less conservative design-basis hurricane. Linear interpolation for sites located between two wind DG-1247, Page 6 contour lines is permitted. 2. Design-Basis