1. 1 DG-1247: Design-Basis Hurricane and Hurricane Missiles for Nuclear Power Plants Brad Harvey, CCM Senior Physical Scientist (Meteorology) U.S. Nuclear Regulatory Commission 14th NUMUG Meeting, Oakbrook, IL, June 27-29, 2011

2. 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 2

3. 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 3

4. F-Scale vs. EF-Scale for Tornado Damage FUJITA SCALE (F-Scale) ENHANCED FUJITA SCALE (EF-Scale) F Number 3 Second Gust (a) (mph)EF Number 3 Second Gust (a) (mph) 045-78065-85 179-117186-110 2118-1612111-135 3162-2093136-165 4210-2614166-200 5262-3175Over 200 4 (a) Wind speed estimates based on observed damage

5. Design-Basis Tornado Wind Speeds REGION RG 1.76, REV 0 (fastest ¼ mile) RG 1.76, REV 1 (3-sec gust) I360 mph230 mph II300 mph200 mph III240 mph160 mph 5

6. Tornado Intensity Regions RG 1.76, Rev 0RG 1.76, Rev 1 6

7. 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. 7

8. Hurricane Wind Speeds 8

9. Development of Design-Basis Hurricane 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 9

10. Design-Basis Hurricane Wind Speeds 10 3-sec gust wind speeds in mph (m/s) at 33 ft (10 m) above ground in open terrain

11. Design-Basis Hurricane Wind Speeds 11 Locations where design- basis hurricane wind speeds exceed those for tornadoes

12. Hurricane Missiles 12

13. Development of Design-Basis Hurricane Missiles Missile Speed V m is a function of: –Wind speed v –Air density ρ –Drag coefficient C d –Missile effective area A –Missile mass m V m = function (v, ρ, C d, A, 1/m) 13

14. Development of Design-Basis Hurricane 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 14

15. Potential Missiles: Rooftop HVAC Equipment 15

16. Design-Basis Hurricane Missile Spectrum 1.A massive high-kinetic-energy missile that deforms on impact Auto 2.A rigid missile that tests penetration resistance Pipe 3.A small missile that tests barrier openings Solid steel sphere 16

17. Design-Basis Hurricane Missile Spectrum MISSILE TYPEDIMENSIONSMASS Auto16.4 ft x 6.6 ft x 4.3 ft4,000 lb Pipe6.6 in diam x 15 ft long287 lb Sphere1 in diam0.147 lb 17

18. Maximum Horizontal Missile Speeds 18

19. Maximum Horizontal Missile Speeds 19

20. 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 20

21. 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 21

22. Thank you! 22 Any questions?