ML17310B229
| ML17310B229 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 03/09/1994 |
| From: | Lewis J ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML17310B228 | List: |
| References | |
| NUDOCS 9404200176 | |
| Download: ML17310B229 (22) | |
Text
Arizona Public Service Company PALO VERDE NUCLEAR GENERATING STATION P.O. BOX 52034
~
PHOENIX. ARIZONA85072-2034 JAMES M. LEVINE VICE PRESIDENT NUCLEAR PRODUCTION 102-02898-JML/RABIJRP March 9, 1994 U. S. Nuclear Regulatory Commission ATlN: Document Control Desk Mail Station P1-37 Washington, DC 20555
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)
Unit 2 Docket No. STN 50-529 Request for Notice of Enforcement Discretion File: 94-055-026 Arizona Public Service Company (APS) hereby requests a Notice of Enforcement Discretion from the PVNGS Unit 2 Technical Specification Limiting Condition for Operation (LCO) 3.8.1.1.b. The existing Technical Specification LCO Action states, "with one emergency diesel generator of 3.8.1.1.b inoperable.... restore the diesel generator to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least HOT STANDBYwithin the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />."
APS is requesting the NRC to exercise discretion in not enforcing compliance with the requirement of the action statement for an additional 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> beyond the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to avoid an unnecessary plant shut down. The additional 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> willallow maintenance and testing to be completed on the "B" emergency diesel generator in order to declare it operable.
If"B"emergency diesel generator is not returned to operable status within the additional 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br />, Unit 2 will be in at least HOT STANDBYwithin the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
The Plant Review Board has reviewed this request for Notice of Enforcement Discretion and determined that the 18 hour2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> extension to the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement does not constitute an unreviewed safety question or create a nuclear safety hazard.
Pursuant to 10 CFR 50.91(b)(1), a copy of this request is being forwarded to the Arizona Radiation Regulatory Agency.
9404200176 940412 PDR ADOCK 05000529 8
(
U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Request for Notice of Enforcement Discretion Page 2 Should you have any questions, please call Richard A. Bernier at (602) 393-5882.
Sincerely, JML/RAB/JRP/rv Enclosure cc:
L. J. Callan K. E. Perkins K. E. Johnston B. E. Holian A. V. Godwin (ARRA)
ENCLOSURE REQUEST FOR NOTICE OF ENFORCEMENT DISCRETION FOR COMPLIANCEWITH LIMITINGCONDITION FOR OPERATION 3.8.1.1.b
f I
Descri tion of Condition On Wednesday, April 6, 1994, the Unit 2 operators started the "B" emergency diesel generator for the monthly operability surveillance test.
The area operator at the diesel identified an unusual noise coming from the engine.
The operator notified the maintenance department to investigate.
The engine was operated for approximately 20 minutes before it was shut down, declared inoperable, and entered the action statement at approximately 1245.
Engineering and maintenance investigated to determine the cause of the noise.
The inspection covers for the 4L cylinder head and 4L cam lobe were removed.
The intake lifters and the crosshead assembly were found in a degraded condition.
During the disassembly of the 4L head to replace the intake lifters and intake crosshead, engineering and maintenance inspected for the cause(s) of the condition.
During the 4L disassembly,
- repair, and reassembly the following inspections were performed:
abnormal component wear foreign material on or in the components abnormal head bushing wear inadequate lubrication bent or distorted parts cam lobes rotated on the cam shaft cylinders for abnormal cam lobe wear The 4L head was reassembled per PVNGS standard work practices.
The new components were installed.
During the maintenance test run the 4L cylinder was noted as having a lower than expected exhaust temperature.
Also the engine analysis, which started at the 4L cylinder had abnormally low cylinder pressures.
The engine was shut down and an inspection was performed.
The initial inspection revealed that the 4L exhaust valves were stuck open.
The exhaust crosshead assembly appeared to be lodged in the crosshead bushing.
A meeting was held with operations, maintenance, and engineering to assess the current situation and address the root cause of failure investigation and repair.
During the meeting, the team decided to remove the 4L cylinder head from the engine and place it in quarantine for a detailed root cause of failure. To repair the diesel, a replacement cylinder head assembly from the Unit 3 "B" diesel was used.
Unit 3 is currently in a refueling outage with the "B" diesel out of service.
This is the most expedient way to restore the unit 2 "B" diesel while maintaining the 4L head intact for root cause analysis.
This work was completed early on Saturday, April 9, 1994. After a visual inspection, the "B" diesel generator was started in preparation for its four hour run and diagnostic evaluation; prior to being declared operable.
Approximately 1~/~ hours into the run, the Page 1 of 4
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fully loaded, "B" diesel generator tripped on an indicated overspeed signal.
At the time ofthe trip Palo Verde personnel were present in the "B"diesel generator room observing the run. According to these individuals, no signs of an overspeed occurred, there was no increase in engine speed or additional noise or vibration at the time of the trip. The "B" diesel generator was running parallel to the grid fully loaded, which would also indicate that there was not an overspeed event.
APS is currently troubleshooting the trip.
Technical Specification Limiting 'Condition for Operation 3.8.1.1.b requires that two separate and independent diesel generators shall be operable.
With one diesel generator of 3.8.1.1.b inoperable, demonstrate the operability of the A.C. offsite source by performing surveillance requirement 4.8.1.1.1.a within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and at least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter; and if the diesel generator became inoperable due to any cause other than preplanned preventative maintenance or testing, demonstrate the operability of the remaining operable diesel generator by performing surveillance requirement 4.8.1.1.2.a.4 within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />; restore the diesel generator to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in cold shut down within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
Therefore, APS is requesting the NRC to exercise discretion in not enforcing compliance with the ACTIONstatement of Technical Specification 3.8.1.1.b.
Otherwise, a plant shut down would be required.
The exercise of discretion is requested to remain in effect for 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> which would allow maintenance to be completed on the "B" diesel generator in order to declare it operable.
Safe Basis The diesel generators are physically and electrically isolated from each other.
Physical separation for fire and missile protection is provided by installing the diesel generators in separate rooms in a Seismic Category I structure.
Power and control cables for the diesel generator and associated switchgear are routed in separate raceways.
Each diesel'generator is capable of supplying the required power to ESF and safe shutdown loads which ensures that the facilitycan be safely shut down and maintain in a shutdown condition for extended periods of time and that sufficient instrumentation and control capability is available for monitoring and maintaining the unit status.
APS engineering has performed a Probabilistic Risk Assessment for having "B" diesel generator inoperable for 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> beyond the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> action statement.
The increase in core damage probability for an additional 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> is 9E-7 while the increase in core This test is required to be completed regardless of when the inoperable EDG is restored to operability.
Page 2 of 4
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damage probability for forced shutdown of the unit with one diesel generator inoperable is 4E-6.
Based on this information, the compensatory actions discussed later in this letter, and the projected weather conditions for this time frame which would not have an adverse impact on offsite power supplies; it can be concluded that there is no significant increase in the probability or consequences of an accident previously evaluated nor will it create the possibility of a new or different kind of accident from any accident previously evaluated.
The probabilistic risk assessment has shown that there is no significant reduction in the margin of safety.
Justification for the Duration of the Re uest The extension of the LCO for 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> beyond the allowed outage time, for one inoperable emergency diesel generator, will provide the opportunity to complete corrective maintenance and subsequent surveillance testing on the "B"diesel generator.
Failure to grant enforcement discretion for the additional 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> would result in an unnecessary plant shutdown and consequent plant transient.
The diesel generator was placed out of service at 1245 on April 6, 1994, to perform troubleshooting due to a noise coming from the engine during the monthly surveillance test.
Inspection determined that the 4L cylinder intake lifters and crosshead assembly were found in a degraded condition. After replacement ofthe degraded components and additional inspections to ensure no other damaged components existed, the engine was reassembled and an engine diagnostic test was started on April 8, 1994.
During the test run, the 4L cylinder exhaust temperature was lower than expected.
An inspection revealed that the exhaust valves were stuck open. At approximately 1600 on April 8, 1994, PVNGS management decided that the entire 4L cylinder head assembly should be removed and placed in quarantine for subsequent root cause of failure analysis.
The removed assembly would be replaced by one from the Unit 3 "B" diesel generator which is out of service during the Unit 3 refueling outage.
The work was completed and the engine testing began at approximately 0400 on April 9, 1994.
As noted above, the engine tripped on an indicated overspeed condition. Atthe time of the engine trip all parameters for the engine were in their normal range.
The additional time is requested to complete troubleshooting of the indicated overspeed trip, corrective maintenance, and testing the engine to ensure operability.
A Probabilistic Risk Analysis was performed to determine the impact on plant risk associated with the extension of the LCO for 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> beyond the allowed outage time.
The analysis assumed that only the "B" diesel generator is out of service.
The core damage probability increases by 9E-7 for an 18 hour2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> extension of the LCO. A forced Page 3 of 4
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outage of Unit 2 with the "B" diesel generator inoperable increases the core damage probability by 4E-6.
Com ensato Actions The redundant emergency diesel generator has been ru'n to prove operability as required by the Technical Specifications.
All redundant train safety equipment has been determined to be operable and Unit 2 Operations will maintain operability of the Train A ESF equipment and diesel generator while in the LCO action statement.
In addition, the non-essential auxiliary feedwater pump willbe verified and maintained fullyoperable, and no non-emergent work will be performed on these components while in this LCO action statement.
Switchyard (525 kV and startup yards) activities are normally performed under the cognizance and direction of the Unit 1 shift supervisor.
Temporary instructions have been provided to Unit 1 to ensure that no interruption of offsite power to Unit 2 occurs while in the LCO action statement.
APS and Salt River Project responsible control centers have been notified of the work being performed in Unit 2 and willtake precautions for the outside distribution system.
No work willbe performed or vehicular access allowed in the switchyard without specific review and approval by the Unit 1 Shift Supervisor and Vice President, Nuclear Production.
Any emergent work in the switchyard will be evaluated for potential affect in the supply of offsite power to Unit 2 and will be authorized by the Vice President, Nuclear Production.
Unit 2 Operations personnel have been briefed on the conditions of this request for enforcement discretion.
They will also be provided with copies of this request and the Notice of Enforcement Discretion.
a APS has confidence that the additional requested time will be sufficient to allow troubleshooting, corrective
- actions, and testing to declare the emergency diesel generator operable with the currently known conditions.
Conse uences to the Environment V
APS has determined that the requested Notice of Enforcement Discretion involves no change in the amount or type of eNuent that may be released offsite, and that there is no increase in individual or cumulative occupational radiation exposure.
As such, operation of PVNGS Unit 2 in accordance with the proposed enforcement discretion, does not involve an unreviewed environmental safety question.
Page 4 of 4
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UNITED STATES NUCLEAR REGULATORYCOMMISSION REGION V 1450 MARIALANE WALNUTCREEK, CAUFORNIA94596-5368 June 4,
1993 Docket:
50-529 License:
NPF-51 CAL:
5-93-003 Arizona Public Service Company P.O.
Box 53999, Station 9082
- Phoenix, Arizona 85072-3999 Attention:
Hr.
W. F.
Conway Executive Vice President, Nuclear
SUBJECT:
CONFIRMATORY ACTION LETTER:
W.
CONWAY LETTER DATED JUNE 2, 1993 This letter is to confirm the commitments made by you in your letter dated June 2,
- 1993, regarding the March 14,
- 1993, steam generator tube rupture at Unit 2 of the Palo Verde Nuclear Generating Station and your ongoing investigation into the cause of the tube failure.
We recognize the significant efforts you have taken to keep the NRC informed of the status of your investigations and the commitments described in your June 2,
- 1993, letter.
We accept these commitments.
In addition, to clarify the commitments in your June 2,
1993 letter, we understand that you will take the following actions:
2.
3.
You will notify the NRC prior to completion of eddy current testing on the Unit 2 steam generators.
The safety analysis you submit to the NRC will include the proposed operating interval to the next tube inspection.
You will not restart the Unit 2 facility until the NRC concurs with the restart of the facility.
Pursuant to Section 182 of the Atomic Energy Act, 42 U.S.C.
- 2232, and 10 CFR 2.204, you are required to:
1)
Notify me immediately if your understanding differs from that set forth above, 2)
Notify me in writing if for any reason you cannot complete the actions specified in your June 2,
1993 letter and as clarified above.
9306160289 930604 PDR ADOCK 05000529 P
Il t
3)
Notify me in writing when you have completed the actions addressed in this Confirmatory Action Letter.
Issuance of this Confirmatory Action Letter does not preclude issuance of an Order formalizing the above commitments of requiring other actions on the part of the licensee.
Nor does it preclude the NRC from taking enforcement action for violations of NRC requirements that may have prompted the issuance of this letter.
In addition, failure to take the actions addressed in this Confirmatory Action Letter may result in enforcement action.
The responses directed by this letter are not subject to the clearance procedures of the Office of Management and Budget as required by the Paperwork Reduction Act of 1980, Pub.
L. No.96-511.
In accordance with 10 CFR 2.790 of the NRC's "Rules of Practice,"
a copy of this letter and its enclosures will be placed in the NRC Public Document Room.
Sincerely, au3 Renber Regional Admini ator CC:
Hr. Steve Olea, Arizona Corporation Commission James A. Beoletto, Esq.,
Southern California Edison Company Mr. Charles B. Brinkman, Hanager, Washington Nuclear Operations Mr..Aubrey Godwin, Director, Arizona Radiation Regulatory Agency
- Chairman, Haricopa County Board of Supervisors Jack R.
- Newman, Esq.,
Newman
& Holtzinger, P.C.
Hr. Curtis Hoskins, Executive Vice President and Chief Operating Officer, Palo Verde Services Roy P.
Lessey, Jr.,
Esq., Akin, Gump, Strauss, Hauer and Feld Bradley W. Jones, Esq., Akin, Gump, Strauss, Hauer and Feld
~r,
bcc:
J. Sniezek,
Lieberman,OE J.
- Roe, NRR E. Adensam, NRR T. quay, NRR C. Trammell, NRR L. Tran, NRR J. Scinto, OGC L. Chandler, OGC J. Goldberg, OGC J. Hitchell, OEDO K. Perkins, RV R. Huey, RV H. Blume, RV G. Cook, RV Docket File
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