ML20236B701

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Forwards Structural Engineering Branch Position on Seismic Design of Plant.Document Sets Forth NRC Position on Reanalysis of Plant for 7.5 Magnitude Earthquake W/ Horizontal Spectra Normalized to .75g
ML20236B701
Person / Time
Site: Diablo Canyon, 05000000
Issue date: 05/07/1976
From: Tourtellotte J
NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD)
To: Silver S
AFFILIATION NOT ASSIGNED
Shared Package
ML20236A877 List: ... further results
References
FOIA-87-214 OL, NUDOCS 8707290201
Download: ML20236B701 (2)
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1 May 7, 1976 DISTRIBUTION Ketchen Davis Tourte110tte Mrs. Sandra A. Silver Skpar l 5055 Radford Avent.e rdt North Hollywood, California 91607 fn[ '

NRC Files In the Matter of . Reg Central

' Pacific Gas and Electric Compa{prmal File (2)

, (Diablo Canyon NuclearJower Plant, Units Nos. I and 2) i Docket Nos. FJ-275 0 L. and 50-323 0.L.

Dear Mrs. Silver:

On April 20, 1976, a meeting was held between the United States Nuclear

. Regulatory Corsaission Staff and Pacific Gas and Electric Company about I the seismic situation at the Diablo Canyon Plant. That meeting was announced to the parties by enclosure 1.

Enclosed for your infonnation is the Nuclear Regulatory Connission's Structural Engineering Branch Position on the seismic design of Diablo Canyon which was distributed to the Applicant by the Staff at the April 20 meeting. You will note that this document sets forth the' ,

Staff p4sition on reanalysis of the Diablo Plantfor a 7.5 magnitude i earthquake with horizontal spectra normalized to .759 Sincerely, James R. Tourtellotte  !

' Assistant Chief Hearing Counsel  !

Enclosures cc: (w/ encl .) Mr. Gordon Silver l Elizabeth S. Bowers, Esq. William P. Cornwell Mr. Glenn O. Dright Paul C. Valentine I Dr. William E. tiartin Yale I. Jones, Esq.

Philip A. Crane, Jr. , Esq. Atomic Safety and Licensing Appeal  ;

Elizabeth Apfelberg Board 1 Andrew J. Skaff, Esq. Atomic Safety and Licensing Board Rayo Flening Docketing and Se Nice Section Mr. Frederick Eissler 8707290201 870721

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!!UCLEAR REGU:. ATCRY CO:"11SSIO:!

STRUCTURAL c^:GIffEERI!!S DPKlCH l

. BRA!!Cl! POS.ITIO:10:! TliE SEIS".IC DESI.G_l_DF DIIS.O CANYO:1 l

l l 1. The applicant will be asked to specify a magnitude 7.5 earthquake at the liOSSRI fault with horizontal spectra ncrmalizcd to 0.75g Regulatory Guide 1.60 spectral shapes may be used. Use of the HOSGRI spectral shape will require further justification since it is believed that the HCSGRI spectral sh pe was developed for lower magnitude earthquakes.

l 2. A reduction in both'. horizontal and vertical response spectra will be permitted depending on the actual equivclent length of individual buildines. This reduction recognizes that grcund motions are not synchronized under structures during earthqua:.es. In other words, different points in the foundation base slab "ill not experience the maximum free field ground motion at the stne time. The quiv-alent length of each individual structure wili be equal to the square root of the building base slab crea. The magnitude of the ,

reduction factor shall be determined as the average of the value l from the theoretical procedure given by Scanita (see Reference) for a harmonic wave and the value deternined using the Pacoima Dam i

record obtained in the 1971 San Fernando earthquake. The harmonim wave in the Scanlan procedure will be assumed to have a frequency of 7 hertz.

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3. Where such reduction in response spectra is uscd, the applicant will be ashed to appropriately account for additional tilting and l torsion which may result from the nonsynchronized earthquake motions considered in item 2, above.

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4. In reevel;2 ting the capability of the picnt structure, systems l

and comprants, inelastic behavior may be relied upon to absorb l the grourd notion energy. Where.such a behavior is relied upcn, a ductili:y ratio not exceedinp 1.2 may be used in determining f

seismic 1:sds and rations. For each particular structure where

- this ductility is relied upon, the applicant will be asked to I k

provide :..Itification cnd bases for assuring that the increased strains r.d deformations will not affect the safety functions of the plant syste:as and structures. This ductility ratio is permitted by the SEB staff for near-field earthquakes, such as those as ::iated with the HOSGRI fault, which tend to have shorter dcrations of strong notion. It is recognized that for short dur-tion ecrti1 quakes, the use of elastic response spectra tends to :roduce overly conservative results.

5. It was also decid3d that the analytical work required to develop individa:.1 rcsponse spectra for the various plant buildings will be perfe-ed by the applicant and a repart will be requested thereaitr. The SED staf f and Dr. Newrurh will review this l report er.: only thercaf ter will finalize the SER for release.

)Q &thvDL Isa S. Sihweil, Chief Structural Engineering Branch  ;

Division of Systems Safety j l

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