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:
etration 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 missiles listed in Table 1 to be capable of striking in all directions with the horizontal velocities shown in Table 2 and with a vertical velocity of 26 m/s. The horizontal missile velocities shown in Table 2 were taken from Table 5 of Reference 10 and represent maximum horizontal missile speeds in open terrain. The vertical missile velocity of 26 m/s bounds all the vertical missiles velocities calculated from Table 2 of Reference 10 which shows terminal total missile velocities (over open terrain) and the associated angle of incidence with respect to the ground. RG 1.76 uses two different automobile missiles as a function of tornado region (i.e., a larger and heavier automobile for tornado Regions I and II and a smaller and lighter automobile for tornado Region III) because the lighter automobile was found to have a higher kinetic energy in Region III as compared to the heavier automobile. However, in the case of the hurricane wind field, the heavier automobile was found to have a higher kinetic energy for all wind speeds as compared to the lighter automobile and therefore the design-basis hurricane automobile missile is based only on the heavier design-basis automobile missile presented in RG 1.76. Barrier design should be evaluated assuming a normal impact to the surface for the automobile and Schedule 40 pipe (6.625 in. diameter) missiles. The automobile missile is considered to impact at all altitudes less than 9.14 m (30 ft) above all grade levels within 0.8 kilometers (0.5 miles) of the plant structures. The hurricane missile analyses presented in Reference 10 are 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