ML18113A996
| ML18113A996 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 03/13/1979 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18113A997 | List: |
| References | |
| TAC-11431, NUDOCS 7903300584 | |
| Download: ML18113A996 (6) | |
Text
e UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of DUQUESNE LIGHT COMPANY OHIO EDISON COMPANY PENNSYLVANIA POWER COMPANY (Beav~r Valley Power Station~ Unit No. 1)
ORDER TO SHOW CAUSE I.
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Docket No. 50~334
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The Duquesne Light Company, Ohio Edison Compa~y, and Pennsylvania Power Company (the licensee) is the holder of Facility Operating License No. DPR-66, which authorizes operation of the Beaver Valley Power Station, Unit No. l (the facility) at power levels up to 2652 megawatts thermal (rated power).
The facility, which is located at the licensee's site in Beaver County, Pennsylvania, is a pressurized water reactor used for the commercial generation of electricity.
IL On December 6, 1978 the licensee filed a Licensee Event Report, LER 78-53, indicating that there were two piping systems for which stress computa-tions in~dvertently had not been completed using a piping analysis computer code.
These systems *have si nee been reanalyzed and design modifications have been completed.
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In the course of this reanalysis, significant discrepancies were observed between the original computer code used to analyze earthquake loadings and a currently acceptable computer code developed for this purpose.
- e In the course ~fa meeting on*March 8, 1979 to discuss these. matters, the*
Licensee informed the NRC staff that the differences in predicted piping stresses between the two computer code*s is attributable to the fact that the piping analysis code specified in the application for an operating l icens~ uses an algebraic summation of the loads predicted_separately by the computer code for both the horizontal component and for the verti-cal component of seismic events. This incorrect treatment of such loads was not recognized at that time.
Such loads should not be alegbraically added {with predicted loads in the negative direction offsetting predicted loads in the positive direction) unless far more complex time-hist cry.
analyses are performed.
Rat her, to properly account for the effec*ts of earthquakes, as required by General Design Criterion 2 for systems impor-ta-nt to safety, such loads should be combined absolutely or, as is the case in newer codes, using techn1ques such.as the square root of the sum of the squares._ This conforms to current industry practice.
The inappropriate analytical treatment of load combinations discussed above becomes significant for piping runs in 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.
It is in these runs that the predicted earthquake loads may differ sig~ific~ntly.
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e e 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 a substantial number of areas of high stress in piping,as well as a number of areas in which there is potential for damage to adjacent restraints or supports, which coul*d have significant adverse effects on the ability of the piping system to withstand seismic events.
In order to ascertain the specific systems that are potentially iffecte~
by this error, members of the NRC staff on March 10, 11 and 12 accompanied the Licensee's representatives to the offices of Stone and Webster, the architect-engineer of the facility to review detailed designs and computa-tions for some of the piping systems of principal potential concern.
Concurrently, on March 9, 1979 the Licensee suspended power operation of the facility.
Based on this more detailed review, the NRC staff has con-cluded that until full renaalysis of all potentially affected piping systems important to safety has been completed with a piping analysis computer code which does not contain the algebraic summation error, the potential for serious adverse effects in the event of an earthquake is suffi ci eritl y widespread that the basic defense in depth _provided __ by r.edundant safety systems may be compromised.
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In view of the safety significance of this matter as discussed above, the Director of the Office of Nuclear Reactor Regulation has concluded that
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e the public heal th and safety requires that the present suspension of operation of the facility should be continued:
(1) until such time as the piping systems for al_l affected safety systems have been reanalyzed for earthquake events to demonstrate conformance with General 'Design Criter_ion 2 using a piping analysis computer -code -which does not contain the error discussed above, and (2) if such reanalysis indicates that there are components which deviate from applicable ASME Code _requirements,
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until such deviations are rectified.
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Accordingly, pursuant to the Atomic Energy Act of 1954, as amended, and the Commission's Rules and Regulations. in 10 CFR Parts 2 and 50, IT IS HEREBY ORDERED THAT the Licensee show cause, in the manner hereinafter
- provided, (1)
Why the Licensee should not reanalyze the facility (2) piping systems for seismic loads on all potentially affected safety systems using-an -appropri"ate piping analysis* computer code which does not combine loads algebraically; Why the Li~ensee should not make any modifications to the facility piping systems indicated by such reanalysis to be necessary; and
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e (3)
Why facility operation should not be suspended pending such reanalysis and.completion of any required modifications
- In view of the importance to safety of this matter, as described herein, the Director of the Office of Nuclear Reactor Regulation has deter-mined that the public health safety or interest require that this action be effective immediately, pending further Order _of the Corrunission.
Accordingly, within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of the receipt of this Order, the_* fai:il ity_
shall be placed in cold shutdown cond1tion, and shall remain in such mode until further Order of the Commission.
The Licensee may, within twenty days of the date of this Order, file a written answer to this Order under oath or affirmation. Within the same time, the Licensee or any interested person may request a hearing.*
If a hearing is requested, the Corrunission will issue an Order designating the time and place for hearing.
Upon failure of the licensee to file an answer w1thin the time specified, the Director, Office of Nuclear Reactor Regulation will, without further notice, issue an order suspending further activities under Operating license DPR-66.
In the event a hearing is requested, the issues to be considered at such
~earing shall be:
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e Whether operation under Facility License No. DPR-66 should be suspended until (1) the piping-systems for all affected safety systems are reanalyzed for earthquake events using-
. an appropriate piping analysis computer code which does not combine seismic loads algebraically, and until {2) any modi-fications required to restore*the system to conformance with applicable ASM Code requirements are completed.
FOR THE NUCLEAR REGULATORY COMMISSION Harold R. Denton, Director Office of ~uclear Reactor Regulation Dated at Bethesda, Maryland*
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day of
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