ML20039E185

Responds to & G Mader ,Expressing Concern of Seismic Safety Commission Re Seismic Analysis Discrepancies at Facility.Extensive Independent Reviews of Plant Being Made.Related Correspondence

ML20039E185
Person / Time
Site:	Diablo Canyon
Issue date:	12/28/1981
From:	Bettinger R PACIFIC GAS & ELECTRIC CO.
To:	Scott S CALIFORNIA, STATE OF
References
NUDOCS 8201060622
Download: ML20039E185 (5)

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77 BEALE STREET. SAN FRANCISCO. CALIFORNIA 94106 * (415) 781 4211. TWX 910 372-6587

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00ChEI!:lG & SEHVK December 28, 1981 BRANCH

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Dear Mr. Scott:

ru This is in response to Mr. George Mader's letter of October 28, and your letter of December 11, 1981, to Mr. B. W. Shackelford which express the

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concern of the Seismic Safety Commission regarding the recent seismic analysis discrepancies at our Diab 1'o Canyon Nuclear Power Plant, and ask certain questions regarding the independent review of that facility.

Our comments on these discrepancies and responses to Mr. Mader's questions are set forth below.

The discrepancies at Diablo Canyon, ' hich have been the subject of very w

extensive media coverage, first came to light when a Pacific Gas and Electric Company engineer discovered an error in past analyses. The error he discovered involved the use of inappropriate acceleration response spectra in the determination of the vertical component of th.e seismic response of certain piping and equipment in the annulus area of the containment building.

Subsequent investigation turned up other discrepancies in the same area, including the use of superseded response spectra, and some inaccuracies in the calculation of piping and equipment i

weights which were used for dynamic analyses.

These were prompt.ly reported to the U. S. Nuclear Regulatory Commission by PGandE.

Studies to date indicate that had these discrepancies gone undetected, no failures would have resulted.

The discrepancies Nere caused by deviations from either acceleration response spectra application procedures or design-related quality assurance procedures. They are not related to a breakdown in on-site inspection.

during construction, as Mr. Mader's letter suggested.

Also, they are not related to' geological considerations, nor to the seismic design level for the plant.

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Mr. Stanley Scott

. -December 28 -1981

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i Chairman, Seismic' Safety Commission c

First, by way'of bacLground information, immediately upon discovery lof these discrepancies, PGandE contracted with Robert L. Cloud Associates, Inc. to perfonn an independent review and reverification ~ program of _ the-Hosgri" analyses performed in 1977. The objective-of this program 'is to-assure that there areino other errors which would affect the seismic qualification of safety-related structures, equipment' or piping.

R. L.

Cloud Associates' personnel are experienced in seismic qualification methods, but had not_previously been involved in these Diablo Canyon t

p analyses. The Cloud program includes the following. elements:

1.

. Review of the applicability of seismic design information.

through the seismic design chain, including external PGanc'E interfaces.

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Independent calculation of seismic design data'and ind_ependent i

seismic qualification of equipment.

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Field' verification that seismically qualified systems and-

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equipment are built and installed accordi.ng to design.-

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Review of-applicability of seismic design information associated.

_ ith the URS/Blume interface.

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The first step in the review is to define the seismic design information chain applicable to Diablo Canyon. The entire flow 'of information'for l'

the.Hosgri requalification is being diagrammed. This diagram'will' illustrate _

x all interfaces, describe the information passing between interfaces, and:

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list responsible organizations for the seismic ~ design work.

For this task,'

the seismic design information_ passing a representative sample of' the -

interfaces will be thoroughly reviewed for correctness.

r The requalification of safety-related stiructures, ' equipment, piping, pipe supports, and conduit supports is being done on a sampling basis. One-

of the major plant structures ~has been chosen for detailed. review. The-dynamic model for this structure will be reviewed for. appropriateness, and the model properties such as masses and stiffnesses will be indepen-

. dently calculated from the drawings. The completed model properties will' be compared to-those used for the Hosgri analysis. -For piping,.a sample.

of 10 piping analyses ~are being chosen for reverification.

Beginning with the drawings, new models will be developed in a completelyfindependent; manner.

The models wi.11 be analyzed with a different computer program from that used for the Hosgri v.clyses, and the resultingipipe stresses.Lsupport)

-loads, and' nozzle loads will be compared with the Hosgri analyses.

Samples of pipe supports, conduit supports, and mechanical equipment will be '

similarly requalified.

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. December 28,'1981

~Chiirman',;S(1smic Safety Comission.

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v D.4 If required, a'dditional sampiing will be done until the desired level of confidence has been obtained. We expect that this review and.

i reverification program by R. L. Cloud Associates will be an effective

'means of restoring public and NRC confidence in our seismic design for

~Diablo Canyon.

Iniddition,.theNRCStaffhasrequestedthatBrookhavenNational Laboratories perfo'rm an independent seismic analysis.of the Diablo Canyon containment annulus area".

PGandE has supplied appropriate weights and-structural pr'cperties-for the analysis.

10n November 19, 1981, the NRC issued an order _ requiring an even broader independent _ design verification program'by a company or companies approved by the NRC, including a review of quality assurance procedures and controls used by service contractors and by the Company for all safety-related structures, systems and components.. Prior to authoriza-

-tion to. proceed with fuel loading, the NRC must be satisfied with the results of the program and with any plant modifications resulting from

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' that pVogram that may be necessary.

Other reports covering non-seismic-4 safety-related activities and Company internal design activities, togetGr.with any required plant modifications, must be completed prior totheNP{aUthorizingtheCompanytoexceed5%ofratedpower.

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s To assist Robert L.. Cloud Associates, Inc., in performing the expanded 3%

T desigp:and quality assurance procedures review requested by the NRC,

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the Company.has retained-R. F.1 Reedy,'Inc., as subcontractor to Cloud

,'to revj'ew quality assurance activities, and Dr. William E. Cooper of

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Teledyna Engineering Services who will independently review the activities ~ performed by Robert L. Cloud Associates, Inc., ar.d its (subcontractors. The work is to be done in two phases:

Phase'I is the N ork required to becompleted before fuel load; Phase II is the work w

j required to be completed before proceeding to power-levels above 5%

of rEted power. We estimate that the Phase I work can be completed by the en fof Jaguary 1982 and the Phase II work by the end of April 1982.

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'Thequestions.jEuaskedandourresponsesareasfollows:

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Q-Do'you believe the process of independent review set s

,up for Diablo Canyon was truly independent as delineated

~ by'the Seismic Safety Comission Policy for independent feview?- 3 9

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A -- Yes.

Th'e Diablo Canyon design has been the subject of

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a number of reviews, several. of them " independent" u[

within the' definition of the Seismic Safety.Comission e

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e Mr. Stanley Scott December 28, 1981 Chairman, Seismic Safety Comission Policy.

Initially, the site geology and plant design were developed by PGandE engineers and independent consultants. Then the site geology and plant design were reviewed by the NRC Staff, which has a technical expertise of its own, and by consultants to the Staff including the U. S. Geological Survey and Dr. Nathan M.

Newmark.

Subsequently the site geology and plant design

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were reviewed by the Advisory Comittee on Reactor Safe-guards (ACRS), an independent group of experts appointed by the Nuclear Regulatory Commission to advise the Commission and the Congress on the hazards of proposed or existing reactor facilities and safety standards.

The ACRS itself retained consultants to assist it in reviewing the Diablo Canyon application. These reviews have included siting considerations such as geology, seismology, and the level of design earthquake, the analytical methods used for design of the plant, acceptance criteria, and on-site inspection during construction. These reviews included design audits, review of sample calculations, and in a limited number of cases, perfonnance of alternative calculations.

When the Hosgri Fault was identified, a major effort by the various entities and their consultants was instituted to determine the plant's compliance with revised design criteria.

In addition, many days of public hearings were held and testimony was had, not only from the Company and its consultants and the Staff and its consultants, but also froni intervenors and their consultants.

The result, as noted by the Licensing Board in its decision, is that Diablo Canyon is the most exhaustively reviewed plant in history.

I might add that the favorable rulings by the Licensing Board have been affirmed by the Appeal Board and the matter is now pending before the Nuclear Regulatory Commission (NRC)l.

In any event we believe these reviews by the NRC Staff, the ACRS, and their various consultants fully meet the requirements for independent review as stated in the Seismic Safety Commission Policy Statement and SSC 81-01.

2.

Q - Since errors apparently arose, where in the process do you believe weaknesses existed which allowed for such errors?

IFor your further infonnation attached as Appendix A is a copy of a more detailed description of the design review to date,

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Mr. Stanley' Scott

-5, December 28, 1981 Chairman, Seismic' Safety Comission b

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Based on. our preliminary evaluation, it appears that problems arose where oar. calculations were not subjected -

to the prescribed checking proccdures, and where infor-mation~was transmitted outside of established engineering

. quality control procedures. We will have a more defilii -

tive answer on conclusion of the design audit and rever_i-

.fication prcgram.

l 3.

Q - What -.if any steps have you taken thus far to' correct the problem in your review process which would be applied to other facilities.

l A - Our efforts to date have been directed towards detection and correction of the errors in seismic design at Diablo l

Canyon, and_ conducting a thorough review.of the procedures which may have contributed to.these ' problems.

Further, j

the R. L. Cloud Associates program will look'for other problem areas before we proceed.

It is anticipated that-one result of these efforts-will be that improvements in certain areas of our design procedures will be made.

4 With respect to the specific points raised in your letter.of December 11, 1981, as you can see from the above, extensive independent reviews of the plant have already been made and yet another independent review of the Diablo Canyon plant will be made'.

It.is our intent to make the results'

.of the review available to you.

I am enclosing a copy of all' correspondence between PGandE and the NRC since September, when the seismic analysis

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problems were first. discovered.

In addition, we will include you on the -

service list for all such future correspondence. This will include the

-interim and final Cloud report..

i I appreciate having the opportunity to coment directly on these concerns of the Seismic Safety Commission.

I trust the infomation contained. herein

.is responsive to your questions.

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Sincerely, f

R.V. BEENGER

.R. V. BETTINGER Chief Civil _ Engineer Attachments l

cc: ~ John A. Blume-j Nunzio J. Palladinov -

G.' A.'Maneatis D. A. Brand i'

P.:A. Crane fi

-J.-0. Schuyler

.J. B. Hoch.

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