ML19249A709
| ML19249A709 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 08/03/1979 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19249A705 | List: |
| References | |
| TAC-11431, NUDOCS 7908240182 | |
| Download: ML19249A709 (10) | |
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of
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)
DUQUESNE LIGHT COMPANY
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OHIO EDISON COMPANY
) Docket No. 50-334 PENNSYLVANIA POWER COMPANY
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(Beaver Valley Power Station, Unit No.1)
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ORDER I.
The Duquesne Light Company, Ohio Edison Company, and Pennsylvania Power Company (the licensee) are the holders of Facility Operating License No. DPR-o6, which authorizes operation of the Beaver Valley Power Station, Unit No.1 (the facil,ity) at power levels up to 2652 megawatts thermal (rated power). The facility, whicn is located at the licensee's site in Beaver County, Pennsylvania, is a pressurized water reactor used for the commercial generation of electricity.
II.
Because certain safety-related piping systems at the facility had been designed and analyzed with a computer code which summed earthquake leads algebraically, the potential existed for comprcaising the basic defense-in-depth provided by redundant safety systems in the event of an eartnquake.
This is due to the fact that the technique of algebraic summation can be non-conservative.
Se safety implications of algebraic sumnation resulted from the possibility that an earthquake, of the type for which plants must be designed, could cause a reactor ccolant system pipe
rupture as well as degrade the emergency core cooling system and other systems designed to mitigate such an accident. Therefore, by Order of the Director of Nuclear Reactor Regula;; ion (the Director) 1P the Nuclear Regulatory Commission (NRC), dated fiarch 13,1979 (44 FR 16511, March 19,1979),
the licensee was ordbred to show cause:
1.
Why the licensee should not reanaly::e the facility piping systems for seismic loads on all potentially affected safety systems using an appropriate piping analysis computer ' ode which does not conbine loads algebraically; 2.
Why the licensee should not make any modifications to the facility piping systems indicated by such reanalysis to be necessary; ind
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3.
Why facility operation should not be suspended pending such reanalysis and completion of any required nodifications.
In view of the importance to safety of this matter, the Order was made ir=ediately effective and the facility was required to be placed in the cold shutdown condition and remain in that mode until further Order of the Commission.
III.
The facility is currently in the cold shutdown condition.
Pursuant to the March 13, 1979 Order, the licensee filed a written answer to t'
the Order by letter dated fiarch 31, 1979.
In that response the licensee stated that it was reanalyzing all potentially affected safety systems for seismic loads using an appropriate method which does not sua leads algebraically.
By letter dated June 19, 1979, the licensee submitted a document entitled,
" Report on the Reanalysis of Safety-Related Piping Systens for Beaver Valley No.1 Unit," dated June 15, 1979. Revisions to this report were submitted by letters dated July 11,18, and 27,1979.
In their letters, the licensee requested that the Commission's March 13, 1979 Order, which requires the plant to remain in a shutdown condition, be modified to permit operation of the unit for a period of six to seven weeks at which time the plant would be shut down for refueling. This request is based on the licensee's finding acceptable results of the reanalysis of the safety-related piping and supports (except as described below) for the Design Basis Earthquake (DBE) loading condition and on their commitment to: (1) shut down the facility if a seismic event occurs which results in accelerations greater than an acceleration level of 0.01 g, the setpoint of the facility accelerometers, and (2) inspect those piping systems and supports which have not been shown to be fully acceptable for the Operating Basis Earthquake (OBE) case (ground acceleration of 0.06 g). This commitment is requ~ red only until such time that the reanalysis for the OBE loading condition, and any necessary modifications, is completed.
The exceptions to the ccnpletion of safety-related systens reanalysis invol ses the Fuel Pool Cooling and Purification System (FPCPS), the River Water e
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System (RWS) and the OBE conditions. The FPCPS is defined in the FSAR as a safety-related system. Ho<ever, since the facility has not completed its first nuclear fuel cycle there is no spent fuel in the fuel pool and the FPCPS is not required to be operational. The failure of this system, in the unlikely everit of an earthquake, will have no effect on the public health and safety, pl ant operation, or plant integrity. For the purposes of the March 13, 1979 Show Cause Order, this system is not included in the reanalysis required for facility startup. The licensee has committed to complete the reanalysis of the FPCPS using acceptable analysis techniques and' complete any necessary modifications to supports before spent fuel is placed in the pool.
The River Water System has an overstress condition in two branch connections located on the discharge line in the turbine building.
Failure of these branch connections in this location will not deprive any component of necessary cooling water and will not affect the functioning and structural integrity of any safety-related systems or components. A portion of the discharge line of the Raw Water Pumps that supplies cooling water to the turbine plant has not been reanalyzed. Although this portion of the piping was originally seismically analyzed using algebraic summation, this portion of the line does not perform a safety-related function and since it is lccated in the forebay of the intake structure its failure will not affect the functioning of any safety-related systems or components. The licensee has committed to complete the reanalysis of the RWS and make any necessary modifications prior to startup following the refueling outage.
,i t-The licensee has ccmmitted to reanalyze the safety-related piping to the CBE conditions and until that reanalysis is completed, to shut dcwn and inspect the facility if a seismic event occurs which results in accelerations greater than an acceleration level of 0.01 g.
Shutdown is the response required by 10 CFR Part 100 for the OBE (0.06 g). This commitment essentially resets the CBE for the plant at 1/6 its previous valve and assures that no degradation of piping, supports, or nozzles will occur which might affect their capability to withstand the DBE.
The staff finds the 0.01 g for shutdown and inspection to be an acceptably conservative level for resumption of operation and until the OBE reanalysis is completed.
By letter dated July 23, 1979, the licensee requested the March 13, 1979 Show Cause Order be terminated in its entirety based on the stated commit-ments and criteria in that 1etter and in Chapter Seven of the 1icensee's June 15,1979 report. This was based on the fact that the licensee has completed the reanalyses for the DBE 1ohding condition, including required modifications, of all safety-related systems with the exception of the Fuel Pool Cooling and Purification System and the River Water System.
The commitments by the licensee in their July 23, 1979 letter would provide a consistent and more detailed " calculations-of-record" of all piping systems and supports where computer analyses for pipe stress are required. Al though this additional effort is not intended to provide an increase in the safety of the plant and is not required by the NRC for facility startup, the effort will establish a record by which the licensee can expedite facility modification in the future.
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The licensee has stated its intent to complete the calculation-of-record effort before startup following the first refueling outage.
Based on the above, the licensee concludes that the analyses and modifications completed to date and commitments made in the July 15, 1979 (as revised) Report and in the July 23, 1979 letter demonstrate that, good cause has been shown:
(1) why the suspension of facility operation should not be continued and the facility be permitted to operate and (2) the March 13, 1979 Show Cause Order should be terminated in its entirety.
The licensee's analyses for operation are being performed using the SHOCK 3 and NUPIPE-SW computer codes, which combine earthquake responses in a manner acceptable to the NRC staff. The reanalyses have resulted in some stresses calculated above allowable.
In such cases, the licensee has recalculated the stresses using soil structure interaction (SSI) methodology with a 20 percent increase in the seismic acceleration between the fundamental periods of 0.4 to 0.55 sec. The staff required this 20 percent increase to be applied to each pipe run after ccmputer calculation of stress and support loads in order to ensure an added factor of conservatism. This methodology, with the 20 percent increase, was approved by the NRC staff in its letter to the licensee dated May 25, 1979.
The means by which piping responses are combined in the codes that are currently a basis for the facility design are summarized belcw:
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PSTRESS/SH0CK 3 This code combines the intramodal responses by the absolute value of response due to the vertical earthquake excitation to the (SRRS*) combir.-
ation of the responses due to the two horizontal earthquake components.
The intermodal conponents are calculated by the SRRS method.
NUPIPE-SW This code conbines intramodal** responses by the SRRS method and combines intermodal responses by SRSS or absolute sum for closely spaced modes.
(NUPIPE-SW and SSI methodology will be the basis for the calc..lation-of-record effort).
The NRC staff has determined that an algebraic summation of responses was not incorporated in.to any of the above listed codes. The NRC staff has further concluded that these codes are acceptable for analyzing the facility piping.
Based on the NRC staff's Safety Evaluation, Attachment A, the staff finds that all safety-relatec' ping systems including the reactor coolant system, engineered safety features, emergency core cooling systams, and all piping systems required to achieve and maintain safe shutdown or required for accident mitigatien have been reanalyzed and required modifications impl emented.
- SRSS - Square Root of the Sun of the Squares.
- Medes are defined as dynamic piping deflections at a given frequency.
Intrancdal responses are the components of force, accent and deflection within a i. ode.
Intermodal responses are the components of force, moment and deflection of all modes.
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IV.
The licensee to date has completed all of the actions identified in paragraphs 1 and 2 of the Order to Show Cause dated March 13, 1979, except for (1) the Fuel Pool Cooling and Purification System, (2) the River Water System, and (3) the OBE conditions.
In addition, the licensee has provided (1) justification for plant operation without the FPCPS in service and with overstressed areas in the RWS, (2) commitments for reanalyses of the FPCPS before spent fuel is placed in the fuel pool, (3) commitments to reanalyze and modify the P.WS prior to startup folicwing the refueling outage and (4) commitments to shut down the facility and inspect all affected systems if seismic accelerations at the site accelerometers exceed 0.01g.
The licensee has, pursuant to paragra;.h 3 of the Order, shown cause why operation of the facility should not remain suspended.
In the July 23, 1979 letter, the licensee has also requested the March 13, 1979 Order be terminated.
The licensee's a;
.r to the Order did not request a hearing. On April 2, 1979, the Pennsylvania Public Utility Commission (PUC) filed a request for a hearing and petition for leave to intevene. On April 9, 1979, the PUC amended the April 2,1979 petition to state that it was requesting a hearing only if one or more of the foll wing conditions exists:
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1.
Any other party is granted hearing.
2.
It is determined by the staff of the Nuclear Regulatory Ccmmission that an extended period of cold shutdown for Beaver Valley Unit No.1 shall be necessary in order to make safety related modifications.
3.
The Nuclear Regulatory Commission staff detennination vis-a-vis the shutdown at Beaver Valley Unit No. I is not forthcoming within a reasonable period of time.
With respect to these Conditions:
1.
No other party has requested a hearing.
2.
Since this Order provides for operation, it does not mandate an extended shutdown to make modifications required as a result"of this Order.
3.
The NRC staff has not received any objection from the PUC regarding the reasonableness of the time within which this action was taken.
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 DETERMINED THAT:
The public health, interest or safety does not require the continued shutdown of the facility, AND '
' 'EREBY CRDERED THAT:
effective this date, the proceeding initiateu oy the March 13, 1979 Order is terminated and the following commitments of the licensee are confirmed and required:
e 1.
The spent fuel storage pool shall not be used to store spent fuel until an acceptable analysis and any necessary modification have been nade to the Fuel Pool Cooling and Purification System.
2.
The reanalysis of and modifications to the River Water System shall be completed prior to startup following the first refueling outage.
3.
The Beaver Valley Unit No. I shall be shut down if the site accelerometers exceed 0.01 g and the 1icensee will inspect all safety-related piping systens which have not been reanalyzed and shown to be acceptable at the 0.06 g level of the OBE.
Prior to resuming operations the licensee will denonstrate to the Commission that no functional damage has occurred to those features necessary for continued operation without undue risk to the health and safety of the public.
FOR THE NUCLEAR REGULATORY CCMMISSION Harold R. Centon, Director Office of Nuclear Reactor Regulation Cated at Bethesda, Maryland this day of
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