ML19241B988
| ML19241B988 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak, South Texas  |
| Issue date: | 06/04/1979 |
| From: | Gossick L NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Hall S HOUSE OF REP. |
| Shared Package | |
| ML19241B989 | List: |
| References | |
| 790614, NUDOCS 7907260082 | |
| Download: ML19241B988 (2) | |
Text
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3......I JUN 4 1979 The Honorable Sam B. Hall, Jr.
United States House of Representatives Washington, D. C.
20515
Dear Congressman Hall:
In response to your letter of May 9,1979 to Mr. Carlton C. Kanneror, I am pleased to provide information on the design of nuclear power plants to resist tornadoes. The level of tornado threat is determined based upon historical tornado occurrences in the site vicinity. The Nuclear Regulatory Commission (NRC) requires that structures, s; stems, and components important to safety be designed to v.ithstand a deiign basis tornado considered.s be the most severe reasonably possiSle in the site vicinity. The physical characteristics of our design bar.is tornado are a maximum windspeed of 360 miles per hour and an atmospharic pressure drop of three pounds per square inch in two seconds.
The effects of possible tornado generated missiles, i::luding wooden planks, steel pipes, utility poles weighing 1500 lbs and a 4000 pound automobile, upon plant safety related structures are considered in cur plant ; valuations. Although we presently consider our specific criteria for tornado design conservative, NRC sponsors ongoing research at universities and government laboratories to expand and refine our know-ledge of tornado characteristics and their effects. An example of this ongoing effort is demonstrated in the reports by Fujita, Mcdonald and Minor on the April 1979 Texas tornacces, enclosure 1 and '.
Conclusions based upon 'he tornado analyses, although preliminary in nature, show the maximun, wind speed of between 225 and 260 miles per hour as con-firming the conservatism of the NRC requirement that safety related structures, systems and components in your region be designed :.o with-stand a maximum 360 miles per hour tornado produced wind speed. The NRC has approved design criteria for the Cananche Peak and Scuth Texas Project plants ncw under construction in the region which include the 360 miles per hour design basis ternado.
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The Honorable Sam B. Hall,
Thus NRC tornado design criteria against extreme tornado generated winds, pressures and a wide spectrum of credible tornado missiles are more con-servative than occurred in April 1979, and are guidelines which serve to assure the safe operation and thutdown capability of nuclear pon'er plants throughout the United States.
I am pleased to have been able to provide you with the NRC tornado design criteria for nuclear power plants.
Sincerely,
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Enclosure:
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Characteristics of the Red River Valley Tornadoes by T. Fujita 2.
Tornado Damage Survey of the Wichita Falls & Vernon Texas Tornadoes by Mcdonald & Minor c5' e
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