ML13333A334
| ML13333A334 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 12/22/1978 |
| From: | Ziemann D Office of Nuclear Reactor Regulation |
| To: | James Drake Southern California Edison Co |
| References | |
| FOIA-79-86, TASK-03-06, TASK-3-6, TASK-RR NUDOCS 7901080056 | |
| Download: ML13333A334 (5) | |
Text
Docket No. 50-206 Mr. James H. Drake DEC 2 2 Vice President Southern California Edison Company 2244 Walnut Grove Avenue Post Office Box 800 Rosemead, California 91770
Dear Mr. Drake:
On October 6, 1978, NRC staff members and our consultants met with representatives of Southern California Edison and your consultants to discuss technical aspects of your proposed Site Specific Earthquake Model (SSEM) for San Onofre, Unit 1.
As indicated in our meeting summary dated October 16, 1978, three major areas require additional resolution before a conclusion can be made with respect to the SSEM.
These areas relate to the Integration of mesh size, slip functions, and appropriateness of certai, parameters, presented in your May 1978 final report on "Simulation of Earthquake Ground Motions for San Onofre Nuclear Generating Station, Unit 1".
In accordance with the understanding reached during the October 6, 1978 meeting, your letter dated October 18, 1978, outlines the first phase of a two phase effort of additional studies in the three areas in question.
You indicated that the results of these studies would be provided by March 1, 1979. This would facilitate a preliminary NRC staff epneJusje on the SSEM adequacy and on the appropriate site specific spectra for San Onofre, Unit 1, on.a schedule consistent with that for other Systematic Evaluation Program SEP) plants.
We believe that the general scope of the additional first phase studies outlined in the enclosure toyour October 18 1978 letter is responsive to our concerns in the three areas of question. However, we cannot predict at this time that your suggested "Resolutions" will constitute complete resolutions of the complex issues. Acceptability of the extent of use of the site specific earthquake program fi the seismic reevaluation of San Onofre, Unit 1 will depend to a large degree on our ability to estimate the uncertainties and to assess the margins in this approach based on the results of the studies. For instance, your proposed "resolution"
) of our comments relating to the slip function is sufficiently vague such M
CS that results of the studies on the two versus three parameter slipfunction, the choice of a constant dynamic stresi dro and 1he possible dependence of slip velocity on static stress drop would have to be examined before any conclusions could be made.
OFIE>
CE SURNAME.................
DATE).........................................
NRC FORM 318 (9-76)
NRCM 0240 U. S. GOVERNMENT PRINTING OFFICES 1976 - 626.624
Mr.
James H. Drake 2 -
iA 2
With regard to the parameter studies, the combined effect of uncertainty in input parameters should also be examined. In particular, an "extreme case" combination should be considered. The effect of a-larger magnitude (7.5) earthquake should also be evaluated especially if an increased slip velocity is assumed to be associated with increased stress drop. If the rupture depth is to be limited to 10 km (as proposed in the original study),
we would expect that you will provide convincing Information supporting this assumption since you have already shown that greater depth results in a substantial increase In high frequency response.
In summary, we would like to emphasize that we have not determined the acceptability of the site specific earthquake program. However, we believe that the results of the SSEM program will be important, along with empirical arguments, in the seismic oeevaluatibn of San Onofre, Unit 1. The criteria to be used in determining the contribution of the additional studies to the resolution of the SSEM adequacy and for selection of the appropriate site specific spectra have not.been resolved and in large measure must wait until the additional studies are completed.
Please keep us informed on the progress of your studies.
Sincerely, Dennis L. Ziemann, Chief Operating Reactors Branch #2 Division of 'perating Reactors cc: See next page DI&TSEIBUTION Qckij JRBuchanan NRC DR ACRS (16)
Local-POR DKDavis ORB #2 Reading CStepp NRR Reading VStello DGEisenhut OELD OI&E (3)
DLZiemann ABurger HSmith BGrimes TERA SURNAME V 1.
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121 1212.2 18 NRC FORM 318 (9-76) NRCM 0240
- W S. GOVERNMENT PRINTING OFFICEs 1976 - 626*624
Mr. James H. Drake
- 3 cc Charles R. Kocher, Assistant General Counsel Southern California Edison Company Post Office Box 800 Rosemead, California 91770 David R. Pigott Samuel B. Casey Chickering & Gregory Three Embarcadero Center Twenty-Third Floor San Francisco, California 94111 David W. Gilman Robert G. Lacy San Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 Mission Viejo Branch Library 24851 Chrisanta Drive Mission Viejo, California 92676 U. S. Nuclear Regulatory Commission ATTN:
Robert J. Pate Post Office Box 4167 San Clemente, California 92672
Mr. James H. Drake
- 2 With regard to the parameter studies, the combined effect of uncertainty in input parameters should also be examined. In particular, an"worst case" combination should be considered. The effect of a larger magnitude (7.5) earthquake should also be evaluated especially if an increased slip velocity is assumed to be associated with increased stress drop. If the rupture depth is to be limited to 10 km (as proposed in the original study),
we would expect that you will provide convincing information supporting this assumption since you have already shown that greater depth results in a substantial increase in hih frequency response.
In summary, we would like to emphalize that we
-on the acceptability of the 4 te specific earthquake program. However, we believe that the results of t d
a d~es will be important, along with empirical arguments, in the seismic reevaluation of San Onofre, Unit 1.
--The=extent= owth ic=hese esnit n
' doThe esaet criteria to be used In determining the contribution of to the resolution of the SSEM adequacy and for selection of the approprfata site specific spectra Please keep us informed on the pgogress of your studies.
jAi Sincerely, Dennis L. Ziemann, Chief Operating Reactors Branch #2 Division of Operating Reactors cc:
See next page DISTRIBUTION Docket JRBuchanan NRC PDR ACRS (16)
Local PDR DKDavis ORB #2 Reading CStepp NRR Reading VStello DGEisenhut OELD OI&E (3)
DLZiemann ABurger HSmith BGrimes TERA OFFICE->-DOR:OR B#2 DOR:SEPB DSE:GB DOR:ORB #2 SURNAME*
ABurger:
DKDavis CStepp DLZiemann DATE 12 78 12/
/78 12/
/78 2/ /78 NRC FORM 318 (9-76)
NRCM 0240 U. S. GOVERNMENT PRINTING OFFICE. 1976 - 626-624
Date ROUTING AND TRANSMn1 mAL SUP TO: game, office symbol, room number, initials Date buildinB, Agency Post)
- 2.
Action File Note and Return pproval For Clearance Per Conversation As Requested For Correction Prepare Reply circulate For Your Information See Me omment investigate Signature Coordination Justify REMARKS bGJ 1A L0 SS A- &"t Z4 Zloe.
DO NOT use this form as a RECCRD of approvals, concurrences, dispos.
clearances, and similar actions FROM: (Nameorg. symbol, Agency/Post)
Room No.-Bldg.
Phone No.
5041-102 OPTIONAL FORM 41 (Rev. 7-76)
Prescribed by GSA U. S.GPO: 1978-0-261-647 3354 FPlAR (41 CFR) 101-11.206