ML19256F496
| ML19256F496 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 12/06/1979 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Grew P CALIFORNIA, STATE OF |
| Shared Package | |
| ML19256F497 | List: |
| References | |
| NUDOCS 7912190264 | |
| Download: ML19256F496 (3) | |
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f DEC 0 61979 Ms. Priscilla C. Grew, Director Department of Conservation State of California 1416 f41neth Street Sacramento, CA 93814 Subje t: Seismic Assessment of Containment Structure Rancho Seco fiuclear Unit 1
Dear Ms. Grew:
In response to your letters dated April 13 and July 5, 1979, requesting liRC to undertake a standard soil-structure interaction analysis in order to confirm that current analytical procedures would yield design specifications for both containment structure and the equipment comparable to those used in the criginal design of Rancho Seco fluclear Plant Unit 1, I have directed my staff to take the following actions:
1.
To reassess the appropriateness of the design earthquake levels in light of the recent information regarding the Foothill Fault System, and 2.
To perform an engineering assessment with regard to the difference between the Housner's spectra and the spectra specified in the Regulatory Guide 1.60 and to assess its safety significance.
While our evaluation of the significance of the Foothill Fault System is still in proso ess, we have completed our preliminary assessment regarding the seismic design of the containment structure. A copy of the assessment report is attached.
Based upon the information obtained frcm the Rancho Seco's FSAR, the assumption that the Foothill Fault System would not change the design earthquake levels, and our experience in assessing the seismic. design of other plants, we conclude that the original design may be less conservative than a design based on current criteria. However, the conservatism built in the seismic design process (namely, the initial selection of the design event, the methodologies for seismic analysis and design, and the structural and mechanical resistance) provide a safety margin which is believed to be adequate against seismic risk at the site. We did not perform any quantative analysis because we do not believe it is appropriate.
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s DEC O q 1979 Ms. Priscilla C. Grew If you have any questions, please contact the NRC Project Manager for the Rancho Seco facility, Mr. D. Garner, (phone 301-492-7435).
Sincerely,
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a hkG'.Ei's hut,bdt h"'Dir'ector Dar Division of Operating Reactors Office of Nuclear Reactor Regulation
Enclosure:
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