ML20126D525

Summary of 780928-29 Meeting in Bethesda,Md Re New Seismic Info Concerning Facility

ML20126D525
Person / Time
Site:	San Onofre
Issue date:	10/05/1978
From:	Quittschreiber Advisory Committee on Reactor Safeguards
To:	Advisory Committee on Reactor Safeguards
References
ACRS-SM-0175, ACRS-SM-175, NUDOCS 8005020167
Download: ML20126D525 (3)

Text

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ACRS Members l SUP9mRY OF SEISMIC PEETDG G3 SAN CNDFRE UNITS 2 AND 3, SEPIENBER 28 AND 29, INS The NRC Staff met with representatives of Southern California Edison Company on Septe:aber 28 and 29,1978 in Bethesda, MD to discuss new seismic related g,

information made available since the construction permits were issued in October 1973. The new information presented was in response to NRC questions  !

. related to the following: ,

i Question 361.35 - Tectonics of Capistrano Embavment I I

The Applicant indicates that an exhaustive in- l l

vestigation has been performed which reinforces ',

their conclusions reached at the CP review  !

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Question 361.34 - Offshore E Fault A;plicant indicates that based on new high reso-lution seismic reflection data this fault does  ;

not exist. ,

Question 361.33 - Bypothesized Offshore Zone of Deformation ,

the Applicant indicates it is not reasonable to call this continuous or capable but they are i unable to prove it.

Information presented in response to these questions by the Applicant will be I j provided in writing within the next few nonths.

It appears the MC Staff's main con rn at this time is the need to define a reasonable offchore earthquake for the 240 m long Hypothesized Offshore I tone of Deformation which comes within 5 miles of the site and extends 4 from Newport - Inglewood fault zone to the north to Rose Canyon fault to l the south (Santa Monica Mountains to at least Baja, California). The NRC j

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Staff at the construction permit stage stated that a 0.67 g D2E was reason-ably conservative. The Licensing Board found 0.67 g DBE with an Intensity X ]

event conservative. Unfortunately, no one at the CP stage bothered to assign a specific earthquake egnitude to the 240 IG1 Hypothesized Offshore Zone of Deformation and to attenuate it to the site. %e NRC Staff is con-I corned that they do not have any technical basis per the requirements of 10 CFR 100, Appendix A for the 0.67 g DBE.

The NBC Staff attempted several times at the September 27th and 2Eith meet-

ing to get the Applicant to assign a magnitude for the largest possible earthquake which could occur on the Hypothesized Offsnore Zone of Deforma-tion but the Applicant refused, telling the NRC Staff that the 0.67 g DBE I 2

and Intensity X were NRC values assigned'at the CP stage. % e Applicant I i

said at the CP stage, and still believes, that it is not reasonable to say  !

that the Hypothesized Offshore Zone of Deformation is capable or continu-3 ous for 240 m; however, they admit that they cannot prove that there has I

! been no movement along this zone for longer than 7,000 to 18,000 years since i f

the features are capped with marine sediments only 7,000 to 18,000 years old. %c Applicant also claims that many of the features in the zone do not represent sea floor faulting but rather gentle folds not characteris-j tic of faults. The Applicant noted that in recorded history a magnitude 6.5 seismic event in the largest earthquake that could be associated with

} the site's tectonic region, which would be considerably less than the ,

t 0.67 g DBE. %e NRC Staff did not appear to be concerned that the 0.67 g l i DBE assigned at the CP stage was too small, but rather that there was no real technical basis for assigning that particular DCE value. I The Appicant discussed several recent seismic events, geological features l discovered, and investigations performed since the construction permits were issued. It appeared to be the opinion of the Applicant and the NRC i Staff that there were no significant problems. We NRC Staff has requested I additional investigation on several onshore lineaments trending in the direction of the site discovered in some high altitude photographs.

The Applicant claims they have investigcted these features and have found that nono are capable faults. The NRC Staff is requesting the details of

} this investigation. '

i I suggest the San Onofre Units 2 and 3 Subcommittee meet with the Apolicant well in advance of the presently scheduled operating license review (scheduled

for the February 1979 ACRS meeting) to look at some of the site related ,

items. Items which the Subcommittee could look at early include the

followino

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1. Seismic events occurring in the area of the San Onofre Site since tne CP review. ,

, 2. "A" and "D" geology features found during excavation for ' l

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, hCPS tienbers 3. New infortcation on onshore and offshore featurcs.

4. Investigation of faults found in the vicinity of the San Onofre Site.

5. Dewatering well cavities.

Several ACES consultants over the past 4 years have been involved with most of those items. ,

i G. R. Quittschreiber Senior Staff Engineer Cf h:3 DM L h3 ..

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