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JUL J 0 1976 Docket Hos.30-275 and Sn-323
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Applicant: Pacific Gas and F.lectric Company (PGAE)
Facili ty: Diablo Canyon !uclear Power Station, Units 1 and 2 (DiabloCanyon)
SUMARY OF ADVISORY C0mITTEE 051 RFACTOR SAFEGUARDS (ACRS) S"0C0mITTEF MEETIt G CONCERNING Tite DIABLO CAi! YON OPERATIMG LICPISE APPLICATION The ACRS subcomittee met in San Luis Gbispo, California on June 25 and June 26, 1976 to discuss the Diablo Canyon Operatinq License Application. A list of attendees is provided in the enclosure.
Background
PGSE had applied for operating licenses for Diablo Canyon in 1973.
Construction of Unit 1 had essentially been completed in April 1076 Ilowever, the review of the operating license application was not yrt completed due to delays associated with evaluating the earthquake potential of the 18 sgri fault. This fault, located about 31/2 miles 0
offshore from the Diablo Canyon plant, had been discovered after th-construction pemits for the Diablo Canyon units were issued.
On May 11, 1976 we had formally issued our evaluation of the earthquake potential of the ilosgri fault. Based on an assessment by the US Geological Survey (USGS) we had stated that a magnitude 7.5 earthquake should be assumed to occur on the llosgri fault and had requested that the applicant reevaluate the plant's seismic capabilities accordingly.
This earthquake is more severe than the earthquakes for which the plant I
wasoriginallydesigned. Although PGSE had not agreed with our assessment of the Hosgri fault s earthquake potential the company was proceeding l
with the reevaluation as we had requested.
At a previous subcomittee meeting on May 21, 1976 the geology and seismology had been discussed and some of the seismic design aspects had been discussed. At this meeting (June 25 and June 26) the remainder of the seismic design aspects which had been developed to date were discussed.
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'fe pmsented a discussion of seismic response analysis an! the differences between the approach that we intended to accept for t%
Diablo Canyon reevaluation and the approaches which are norra11y employed. The two pric'ary differences which the staff hr.d adopted were as follows:
(1) In the Diablo Canyon reevaluation it would be acceptable to take cmdit for a st'all amount of non-linear or inelastic behavior.
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In the Diablo Canyon reevaluation it would be acceptable to revise the design response spectrum, depending upon the equivalent length of building foundations, in recognition of the lack of synchronization of ground motion waves beneath structures during earthquakes.
Dr. John Blume, consultant to PG8E discussed the design response spectra (ground motion) to be used as an input to the engineering calculations in the reevaluation. He provided preliminary recormended spectra, based on analyses of the available records for ground motion due to nearby earthquakes at mck sites. Dr. Blume also discussed conservatism in the seismic design of nuclear power plants and compared it to the seismic design of schools, hospitals and other important structures in Califomia. Finally, he discussed the historical experience with the performance of structures in actual earthquakes and related it Mi to nuclear power plant design.
Westinghouse discussed the msults of studies of the reactkcoolant system which had been perfomed based on various assumed design response spectra.
Although the Westinghouse studies had not yet been submitted, Westinghouse intended to proposed and justify combining the loss-of-coolant accident i
loads with the earthquake loads using the square root of the sum of the i
squares instead of following the usual procedure which consists of 3
adding the absolute values. It appeared that, if this approach is used, I
I the mactor coolant system would be able to meet the faulted condition limits of the ASME Boiler and Pressure Vessel Code without the necessity of performing a' time-constsning inelastic analysis.
Dr. Nathan Newmark, an NRC consultant, presented a discussion of the seismic design bases to be used in the mevaluation. The U.S. Geological Survey had specified the ground motion to be utilized in tems of acceleration and other values that would be measured by an instrinnent in the fue field. These values did not account for the presence of structures or the natum.of structural responses such as non-linear energy I
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Dr. Nov.rark had deternined the effective acceleration and provided tentative design response snectra to be used as an input for ennineering calculations. He discussed the bases for this work and related the tentative spectra to observed cround notion data and structural response data frer actual earthquakes.
9r. *!emark also connared the tentative recomendations to the seismic desian bases used for critical structures other than nuclear power plants.
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The tentative design response spectra which had been developed independently by Dr. 'f wnark and Dr. Blume showed substantial similarity but there were some differences between them. t!e noted that our final conclusions on the spectra would not he available until we and Dr. Me'cark had reviewed a specific proposal, with justifications, which PG'.E was expected to submit in the near future. After the final conclusions had been made concerning the design response spectra, the reanalysis would be connleted.
A full ACRS neeting was scheduled for July 11, 1976 to discuss the material we had presented to date at the subcomittee r:'eetings on May 21 and June 25 and 26. Further meetings would he schedule-d when the results of the reanalysis of the plant were available.
Odginal Signed By NNermd Dennis P. Allison D. P. Allison, Project Manager e
Light Water Reactors Branch Ho.1 Division of Project Management
Enclosure:
As stated j
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_ ist of Attendees L_
June 25 and.'une 2r., 197c ACRS t!RC Staff
- 3. Okre4h - Subcommittee Chaiman R. DeYoung J. Ebersole K. Kaour D. Allison ACRS Consultants I. Sibweil J. C. Stepp T. Pickel W. Gamill J. Hilson R. flofmann
- l. Newnark - University of Illinois A. Bates T. Hirons - LASL PGSE Menhors of the General public W. Lindblad A nunber of interested persons
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R. Bettinger from the general public were F. Moutz present. Nonc made statements W
J. Hoch to the subconmittee.
J. Ghomley J. Skylar P. Crane PG&E Consultants J. B1tane
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R. Gallagher j
D. Hamilton I
S. Smith l
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W. Gangloff P. Lin T. Esselman i
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JUL 3 01976 Docket Nos. 0-275 and 50-323 Applicant: Pacific Gas and Electric Concany (PGAE)
Facility: Diablo Canyon ?!uclear Pov.er Station, Units 1 and 2 (Diablo Canyon)
SUMMARY
OF ADVISORY COMfiITTEE ON REACTOR SAFEGUARDS (ACRS) MEETIllG CONCERNIllG Tile DIABLO CANY0l! OPEPATI"G LICEficE APPLICATI0M The ACRS met in Washington, D. C. on July 8,1076 to discuss the Diablo Canyon Operating License application. A list of attendees is provided in the enclosure.
Backaround q,
PG&E had applied for operating licenses for Otablo Canyon in 1973.
Construction of Unit 1 had essentially been conolcted in Anril 1976
!!owever, the review of the operating license apclication was not yet completed due to delays associated with evaluating the earthquake potential of the ?'osqri fault. This fault located about 31/2 niles offshore from the Diablo Canyon plant, had t:cen discoverod after the construction Demits for the Giablo Canyon units vere issued.
On May ll,1976 we had fannally issued o'ur evaluation of the earthouake potential of the !!osgri fault. Cased on an assessment by the US Geological Survey (!!SGS) ve had stated that a mannitude 7.5 earthouake should be assumed to occur on thn Hosgri fault and had reauested that the applicant reevaluate the plant's seismic canabilities accordingly.
This earthquake is more severe than the carthquakes for which the plant was originally designed. Althounh PME had not acreed with our assessnent of the Posgri fault's parthcuaFe potential the comnany eas proceeding with the reevaluation as we had renu sted.
Geolony, seismology. ar.d the seis~ic design (reevaluotion) aspects which had been developed to date had been discussed at f. CPS subcomittee naetinos on "av P1, June 75 and Juna 20, 107C.
At this acetina (July 9,1"7f) t% sono tonics vere discussed with tv fill f.CRS.
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Seismicit.y F. McKeown of the USGS briefly sumarized the USGS assessment. lie stated that. in order to be conservative, it had been necessary to consider: (1) that the 1927 earthquake with a regnitude of about 7.3 (or possibly somewhat less) could have occurred on the Hosgri fault or, altamately, (2) that fault length considerations could lead to a similar magnitude detemination.
It was noted that no earthquakes of magnitude 7.5 or greater were known to have occurred, in the West, except on the San Andreas fault system.
D. Hamilton and Dr. S. Smith sumarized PGAE's interpretations of geology and seismology, which had led to an earthquake with a magnitude of about 6.5.
Dr. S. Smith noted that, in his view, the most likely interpretation of all the evidence indicated that the 1927 earthquake was not on the Hosgri fault.
Seismic Desfon Dr. ?!athan Newark, an FP.C consultant, presented a discussion of the seismic design bases to be used in the reevaluation. Tha U. S. Geological Survey had specified the ground notion to be be utilized in tems of acceleration and other values that would be measured by an instrument in the free field. These values did not account for the presence of structures or the nature of structural responses such as non-linear energy absorbing mechanisms in structures. Dr. Nemark had detemined the effective acceleration and provided tentative design response spectra to be used as an input for engineering calculations. He discussed the bases for this work and related the tentative spectra to observed ground motion data and stmetural response data fmm actual earthquakes. Dr. Fewmark also compared the tentative rectreendations to the seismic design bases used for critical structures other than nuclear power plants.
I Dr. John B1me, consultant to PGSE, also discussed the design responso spectra (ground motion) to be used as an input to the engineering calculations in the reevaluation. He provided preliminary recemnanded spectra, based on analyses of the available records for ground notion due to nearby earthquakes at rock sites.
Sct)edule/ Future $1eetinos The tentative design response spectra which had been developed independent 1v l
by Dr. Nemark and Dr. Blume showed substantial sinilarity hnt thern were some differencies between then. He noted that our final conclusions
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.. JUL 3 01976 on the spectra would not be available until we and Dr. Mem1rk had reviewed a specific proposal, with justifications, which PGriE was expected to submit in the near future. After the final conclusions had been nade concerning the design response spectra, the reanalysis would be completed. PG8E intended to submit the infonration concerning design response spectra shortly and hoped to submit results of the reanalysis in tire to support an tugust 1976 subcommittee reeting.
The cocmittee agreed to provide, through the ACRS staff, any remaining questions on the material presented to date so that they coul.1 be accounted for in a timely manner during the reanalysis of the plant.
Originalsigned By Dennis P. AlliS0"
- 0. P. Allison, Project Manager Licht Mater Reactors Franch !'o.1 Division of Project "aragemant
Enclosure:
As stated cc: Service List LWRf
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ENCLOSURE List of Attendees July 8, 1976 ACRS 95tC Consultants D. Moeller - Chalfman J. Devine - USGS M. Bender F. McKeown - USGS J. Arnold T. Hirons - LASL S. Bush N. Newmark - University of Illinois M. Carbon H. Isbin PGAE
!!. Kerr S. Lawroski W. Lindblad J. Mark J. Hoch D. Owed R. Bettinger it. Plesset V. Ghio C. Siess G. Blane H. Etherington N
J. Ebersole PGAE Consultants ACRS Consultants S. Smith D. Hamilton
'i. Whi te J. D1ume J. Wilson '
R. Gallagher ACRS S_taff Westinchouse Electric Corporation J. ficKinley C. Eicheldinger A. Bates W. Gangloff J. Jacbbs C. W. Lin R. Fraley
't. Libarkin
!RC Staf
- c. UcYouno J. Stolz tf. Garnill J. C. Stepp R. l'ofmann
- 1. :'nicht K. l'apur R. Posnak P. Y. Chen S.18anauer J. Metr' ore e=*
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