Document: NRC Regulatory Guide
Document ID: 171a124d-54d4-4a50-8f5f-f063d9b686c9
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:
e the use of a probabilistic assessment as the sole basis for assessing how well the plant is protected against hurricane missile damage. Protection from a spectrum of missiles (ranging from a massive missile that deforms on impact to a rigid penetrating missile) provides assurance that the necessary structures, systems, and components will be available to mitigate the potential effects of a hurricane on plant safety. Given that the design-basis hurricane windspeed has a very low frequency of occurrence, to be credible, the representative missiles must be common items around the plant site and must have a reasonable probability of becoming airborne within the hurricane wind field. Design-Basis Hurricane Missile Spectrum To evaluate the resistance of barriers to penetration and gross failure, the hurricane missile velocities must also be defined. In addition to the report on design-basis hurricane windspeeds (Ref. 7), the NRC also commissioned a report on design-basis, hurricane-borne missile velocities (Ref. 10). This report describes the method used to calculate the horizontal and total velocities associated with several types of missiles considered for different hurricane windspeeds. The 1 The 75 mph wind speed criterion for generating wind-borne missiles is from the March 2007 Revision 1 to RG 1.76 (Design-Basis Tornado and Tornado Missiles for Nuclear Power Plants) (see pg 6). It is not based on the minimum wind speed to designate a hurricane. DG-1247, Page 5 selected design-basis hurricane missile spectrum for nuclear power plants is the same as the design- basis tornado missile spectrum presented in RG 1.76. This spectrum includes (see Table 1) (1) a massive high-kinetic-energy missile that deforms on impact (an automobile), (2) a rigid missile that tests penetration resistance (a pipe), and (3) a small rigid missile of a size sufficient to pass through any opening in protective barriers (a solid steel sphere). The NRC considers the design-basis hurricane