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DG-1247: Design-Basis Hurricane and Hurricane Missilesfor Nuclear Power Plants Brad Harvey, CCM Senior Physical Scientist (Meteorology) U.S. Nuclear Regulatory Commission 14th NUMUG Meeting, Oakbrook, IL, June 27-29, 2011
Presentation Topics • Why a new Regulatory Guide on Hurricanes? • Development of Design-Basis Hurricane Wind Speeds (NUREG/CR-7005) • Development of Design-Basis Hurricane Missiles (NUREG/CR-7004) • Conclusions
Background on Why a Reg Guide on Hurricanes? • RG 1.76: Design-Basis Tornado • Revision 0 (April 1974) • 2 years of tornado data • Fujita scale used for tornado classification • Revision 1 (March 2007) • 53 years of tornado data • Enhanced-Fujita scale used for tornado classification
F-Scale vs. EF-Scale for Tornado Damage (a) Wind speed estimates based on observed damage
Tornado Intensity Regions RG 1.76, Rev 0 RG 1.76, Rev 1
Why a Reg Guide on Hurricanes? • The maximum design-basis tornado wind speed (360 mph) in Rev 0 of RG 1.76 was considered to be bounding • With the decrease of design-basis tornado wind speeds in Rev 1 of RG 1.76 (200-230 mph), design-basis tornado wind speeds may not bound design-basis hurricane wind speeds in all areas of the U.S.
Development of Design-BasisHurricane Wind Speeds • NUREG/CR-7005 • Design-basis wind speeds correspond to an exceedance frequency of 10-7 per year • Same as for tornadoes • Hurricane simulation model based on ASCE/SEI 7-05 approach • Peak-gust wind speeds generated at 3,575 grid points • A stratified sampling approach used to simulate 10 million years of data
Design-Basis Hurricane Wind Speeds 3-sec gust wind speeds in mph (m/s) at 33 ft (10 m) above ground in open terrain
Design-Basis Hurricane Wind Speeds Locations where design-basis hurricane wind speeds exceed those for tornadoes
Development of Design-BasisHurricane Missiles • Missile Speed Vm is a function of: • Wind speed v • Air density ρ • Drag coefficient Cd • Missile effective area A • Missile mass m Vm = function (v, ρ, Cd , A, 1/m)
Development of Design-BasisHurricane Missiles • NUREG/CR-7004 • Equations of motion are solved for a missile embedded in a hurricane wind field • Changes in horizontal wind field are small • Wind speed varies with height above ground • Missiles start their motion with zero velocity at a height of 40 meters AGL • Missile drag coefficient is constant • Not dependent on missile position or speed
Design-Basis Hurricane Missile Spectrum • A massive high-kinetic-energy missile that deforms on impact • Auto • A rigid missile that tests penetration resistance • Pipe • A small missile that tests barrier openings • Solid steel sphere
Maximum Horizontal Missile Speeds • The same missile has a higher maximum velocity in a hurricane wind field than in a tornado wind field with the same maximum (3-sec gust) wind speed • Tornado missiles are subject to the strongest winds only at the beginning of their flights • Hurricane missiles are subjected to the highest wind speeds throughout their trajectory
Conclusions • Design-basis hurricane wind speeds are higher than those for tornadoes along the coastline south of the border between North Carolina and Virginia • Maximum: 290 mph in the Florida keys • Airborne missiles fly faster in a hurricane wind field as compared to a tornado wind field of the same strength
Thank you! Any questions?