ML20244A556

Answer to NRC 790313 Order to Show Cause.Will Reanalyze Seismic Loads on Piping Sys & Will Modify Sys Where Necessary.Expects to Submit Documented Results by 790424. Believes NRC Should Examine S&W Analyses

ML20244A556
Person / Time
Site:	Beaver Valley
Issue date:	03/31/1979
From:	Schaffer S DUQUESNE LIGHT CO.
To:
Shared Package
ML20244A555	List: ML20244A550 ML20244A556
References
TAC-11431, NUDOCS 7904050216
Download: ML20244A556 (4)

Text

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NUCLEAR REGULATORY COMMISSION q, In the Matter of ) g2

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DUQUESNE LIGHT COMPANY OHIO EDISON COMPANY PENNSYLVANIA POWER COMPANY

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9 Unit No. 1)

LICENSEE'S ANSWER TO ORDER TO SHOW CAUSE 1

On March 13, 1979, the Director of the Office of Nuclear Reactor Regulation issued an Order to Show Cause to Duquesne Light Company, Ohio Edison Company and Pennsylvania Power Company (Licensee) relating to the seismic '

design of certain piping systems at Beaver Valley Power Station, Unit No. 1.

The order requires Licensee to show cause:

(1) why Licensee should not reanaly'ze those facility piping systems which were analyzed by a computer code using an algebraic summation of the loads predicted separately for the horizontal and vertical ,

components of seismic events, such reanalysis to be performed using an appropriate piping analysis computer code which does not combine loads algebraically, (2) why Licensee should not make any modifications to the facility piping systems indicated by such reanalysis to be necessary, and (3) why facility operation should not be suspended pending such rea+41ysis and completion of any required modifications. The order furthec.

required that Unit No. 1 be placed in cold shutdown condition within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of receipt of the order by Licensee and that the facility remain in such mode until further order of the Commission.

In response to the three issues on which Licensee is ordered to show cause, Licensee answers as follows:

1. Why the Licensee should not reanalyze the facility piping systems for seismic loads on all potentially affected safety systems using an appropriate piping analysis computer code which does not combine leads algebraically.

The Licensee will reanalyze the seismic load for affected facility piping systems using an appropriate piping analysis computer code which does not combine loads algebraically.

2. Why the Licensee should not make any modifications to the facility piping systems indicated by such reanalysis to be necessarv.

Licensee will make any modifications to the affected facility' piping systems which it determines to be necessary based on the analysis.

3. Why facility operation should not be suspended pending such reanalysis and completion of any required modifications.

Licensee-has undertaken the program discussed below for reanalysis of the affected piping systems. Upon completion of the reanalysis of, and Y

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(2) any necessary modifications to the affected piping systems required to assure safe shutdown capability and the capability of affected piping systems associated with the Engineered Safety Features'and the Emergency Core Cooling System, we request that the facility be permitted to resume operation pending completion of reanalysis of the balance of the affected piping systems and any necessary modifications of the remaining affected piping systems.

Reanalysis of piping stress (with a code which does not use an algebraic summation technique) and evaluation of supports in those piping runs, which were originally analyzed using an algebraic summation technique and which are part of systems necessary to assure safe shutdown, and the operability of engineered safety features, or emergency core cooling, are being conducted on a 2 shift per day (10 hrs / shift) basis.

As of March 30, 1979, 66% of the pipe stress computer runs were completed.

The remaining runs should be completed by April 3, 1979. Of the completed runs, 90% are acceptable and 10% are presently undergoing reanalysis.

As of March 30, 26% of the pipe support design reviews were completed.

Of the completed pipe support design reviews, 63% are acceptable, 28%

are presently undergoing further evaluation and 9% are undergoing detailed analysis, as applicable. Completion is scheduled for April 20, 1979.

Related design reviews of equipment associated with these piping systems should also be completed by April 20, 1979.

Assuming the same rate of progress as recently experienced, we expect to submit documentation of the results to the NRC starting on April 10 and continuing to completion on April 24, 1979.

In accordance with the requirements of 10 CFR 2.202(b), Attachment A hereto sets forth Licensee's admission or denial of the allegations and charges made in the order.

The NRC order temporarily suspending operations was issued in the absence of sufficient information to assess the seismic design capabilities of the affected piping systems. We believe it is incumbent upon the NRC, however, to consider and evaluate the engineering analyses and data being developed by Stone and Webster. NRC should determine on the basis of that information whether there is a sufficient threat to the public health and safety to warrant the drastic step of a further order continuing the shutdown of Unit 1 pending the reanalysis and possible modification of all affected piping systems regardless of their importance to the public health and safety.

DUQUESNE LIGHT COMPANY

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By tw ; // . 4 6 2 ~

/ Stanley p. Schaf fer,/

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? . ,J Specific Answer to Each Allegation # ,,3 L or Charge in the Show Cause Order S[SC g h

Paragraph I is admitted.

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,M*, T", n Paragraph II, first sentence is admitted to the extent that ensee" i filed a Licensee Event Report, LER 78-53, indicating that the. -

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piping systems for which stress computations had M t been comp *>

go a piping analysis computer code.

With respect to Paragraph II, third sentence, it is admitted that, in.the course of reanalysis, discrepancies were observed between the original computer code used to analyze earthquake loading for certain facility  ;

piping systems and a currently acceptable code (P Stress and the related algebraic summation subroutine, and NuPipe. respectively).

Paragraph II, fourth sentence is admitted.

Paragraph II, fifth sentence, the Licensee is without sufficient knowledge to admit or deny.

Paragraph II, sixth sentence, is admitted to the extent that ,

algebraic summation without time history analyses can, in certain cases, yield lower calculated stresses than those calculated using techniques such as the square root of the sum of the squares.  !

Paragraph II, seventh and eight sentences are admitted to the extent that current industry practice accounts for the effects of earthquakes by combining intramodal forces absolutely, or using techniques such as the square root of the sum of the squares, but it is denied that General Design Criterion 2 specifically requires these load combination techniques.

Paragraph II, ninth and tenth sentences, are admitted to the extent that the algebraic summation technique can become significant for piping runs for which the horizontal seismic component can have both horizontal ,

and vertical components on piping systems and the vertical seismic component also has both horizontal and vertical components, and that in i such runs, the calculated earthquake loads may differ from those calculated using techniques such as absolute combination or the square root of the sum of the squares.

Paragraph II, eleventh sentence, is admitted to the extent that '

although the greatest differences in predicted loads would tend to be limited to localized stresses in pipe supports and restraints or in weld attachments to pipes, there could be areas of higher than originally calculated stress in piping as well as areas in which there is potential for damage to adjacent restraints or supports, which could affect the ,

ability of the piping system to withstand seismic events.  !

I Paragraph II, twelfth sentence is admitted to the extent that members of the NRC staff on March 10, 11 and 12 accompanied the Licensee's representatives to the offices of Stone & Webster, the architect-engineer of the facility, to review detailed designs and computations for some of the piping systems of principal potential concern to the staff.

Paragraph II, thirteenth sentence is admitted.

Paragraph II, fourteenth and fifteenth sentences are conclusions drawn by the NRC staff, and therefore do not require an answer.

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COMMONWEALTH OF PENNSYLVANIA) 1

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COUNTY OF ALLEGHENY- ) .

On this 31st day of March, 1979, before me, Donald W. Shannon, {

a Notary Public in and for said Commonwealth and County, personally appeared S. G. Schaffer, who being duly sworn, deposed, and said that (1) he is President of Duquesne Light, (2) he is duly authorized to execute and file the foregoing Submittal on behalf of said Company, { '

and (3) the statements set forth in the Submittal are true and correct to the best of his knowledge, information and belief.

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1 DONALD W. SHANNON Notary Public Pittsburgh, Allegheny Co.. Pa.

)!y Commission Empires June 7,1979 l

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