ML20217A303
| ML20217A303 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/16/1998 |
| From: | Jeffery Wood CENTERIOR ENERGY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 1-1149, NUDOCS 9803240357 | |
| Download: ML20217A303 (4) | |
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DavisBesse Nuclear Power Station
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John K. le6cd 419-249-2300 Vice President. Nuclear far 419-3214337 Docket Number 50-346 License Number NPF-3 Serial Number 1-1149 March 16, 1998 United States Nuclear Regulatory Commission Document Control Desk -
1 Washington, D. C. 20555-0001
Subject:
Change to Commitments for the Auxiliary Feedwater Pump Turbine and Integrated Control System Prevr stive Maintenance Schedule -
Ladies and Gentlemen:
On September 10,1985, the Toledo Edison (TE) Company submitted the Davis-Besse Nuclear Power Station (DBNPS) Course of Action Report (COAR) for the June 9,1985, event (TE Serial Number 1182). Areas of concern related to the event were identified in the enclosure to the NRC Confirmatory Action Letter dated August 14,1985 (TE Log Number 1798). After evalaation of the TE responses to the June 9 event, the NRC published, on Junes 10,1986, the Safety Evaluation Report, NUREG 1177 (TE Log Number 1997) related to the restart of the DBNPS following the event.
The COAR identified actions required to satisfy the areas of NRC concern. As a result of improved actions implemented since the COAR was submitted, TE has concluded that
. commitments for the following components and systems should be clarified and/or revised:
- 1. Auxiliary Feedwater Pump Turbine Overspeed Trip Mechanism Preventive Maintenance
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- 2. -Integrated Control System Preventive Maintenance bl0l The attachment to this letter contains the background, justification and statement of the revised commitments. These commitments are being revised to support the scope of work identified for the DBNPS eleventh refueling outage which is scheduled to commence on April 11,1998. In accordance with the Nuclear Energy Institute," Guidance for Managing NRC Commitments,"
- accepted by the NRC as documented in SECY-95-300, TE is informing the NRC of these.
changes, but is not requesting NRC approval prior to implementatian.
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Docket Number 50-346 License Number NPF-3 Serial Number 1-1149 Page 2 Should you have any questions or require additional information, please contact Mr. James L.
Freels, Manager - Regulatory Affairs, at (419) 321-8466.
- Very truly yours,
/
LM/laj cc:
A. B. Beach, Regional Administrator, NRC Region III S. J. Campbell, DB-1 NRC Senior Resident Inspector A. G. Hansen, DB-1 NRC/NRR Project Manager Utility Radiological Safety Board l
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Docket Number 50-346 License Number NPF-3 Serial Number 1-1149 Attachment '
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Page1 REVISED COURSE OF ACTION REPORT COMMITMENTS
- 1. Auxiliary Feedwater Pump Turbine (AFIYT) Overspeed Trip Mechanism Preventive Maintenance Toledo Edison (TE) submitted Revision 3 of the Davis-Besse Nuclear Power Station (DBNPS) Course of Action Report (COAR) on October 31,1985 (TE Serial Number 1202).
Action Plan ID addressed the findings, corrective actions and generic implications for the AFPT trip and throttle valve concerns. Eight required corrective actions were identified to address the difficulty in relatching and opening the trip and throttle valve. These eight required actions addressed human factors, procedural, and training considerations for the identified root causes. The root causes and corrective actions were identified and accepted in the Safety Evaluation Report (SER), NUREG 1177.
In Action Plan 1D, revision 3, TE proposed additional planned actions to correct discrepancies noted during the investigation that were not related to the direct and root causes for the trip and throttle valve. Specifically, TE committed to institute a refueling outage preventive maintenance (PM) item to:
- 1) perform non-destructive examination of the tappet leaf spring
- 2) confirm proper adjustment of the tappet
- 3) perform dimensional inspection of the tappet nut and head lever, connecting rod to trip hook lever, and trip hook to latch-up lever mating surfaces.
Action Plan ID stated that these PM actions were to be completed prior to the next refueling outage. In April,1986, TE documented internally the intent to perform the refueling outage PM activity every 5 years. During funher review by TE, no documentation is apparent that provides a direct NRC response that a 5 year periodicity was reviewed by the NRC. The NUREG 1177 states,"the licensee identified additional planned actions to correct discrepancies noted during the course of its investigations. These actions include...,
preventive maintenance....." These PM activities were initially completed during the fifth refueling outage in November,1988. The PM activity was subsequently performed in 1993 and 1996 for AFPT l-2 and in 1993 for AFPT 1-1. Guidance supplied by the Terry Turbine Maintenance and Troubleshooting Guide recommends that an internal inspection be performed every five to eight years. By this letter, Toledo Edison is notifying the NRC of the as performed frequency and revising the PM frequency to be coasistent with the current manufacturers recommendations for inspections one and three listed above.
Toledo Edison has concluded that performance of the internal inspection PM activities at the frequency recommended by the manufacturer is acceptable. Therefore, based upon the recommendation of the equipment raanufacturer, and based upon the past maintenance and
4,;.7 Docket Number 50-346 License Number NPF-3 Serial Number 1-1149 -
Page 2 operating history of the equipment at the DBNPS, PM items one and three above will continue to be performed at the PM frequency recommended by the manufacturer. In support of this conciusion, the following information is offered but is not to be considered as
- additional commitments. The AFPT overspeed trip mechanism is functionally tested in its -
entirety each refueling outage under periodic tests. Inspection of the overspeed trip linkage and adjustment of the overspeed trip tappet are performed at least twice each operating cycle under separate PM activities. The capability to trip and reset the overspeed trip linkage through the manual trip feature is verified monthly during the performance of surveillance -
tests.:The non-destructive examination inspection of the AFPT tappet leaf springs mquires a complete turbine disassembly. During the past performance of this inspection, no cracking of the internal leaf springs has been identified at the DBNPS that could impact the operation of the trip mechanism.
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- 2. Integrated Control System (ICS) Preventive Maintenance Action Plan 16 of the DBNPS COAR addressed the findings, corrective actions and generic implications as a result of unexpected main steam header pressure fluctuations after the plant trip on June 9,1985. As a result of the investigations conducted after the event on June 9, the main steam header pressure fluctuations experienced were determined to be the expected thermal-hydraulic responses for the steam generator conditions, equipment operatien, and operator actions that occurred during the event. The required corrective actions for Action
. Plan 16 centered around operator practices for post-trip manual steam header pressure control, atmospheric vent valve (AVV) and rapid feedwater reduction control setpoints, and inspection of the main steam safety valves. Corrosion of electrical contacts in an AVV module was also noticed and an additional planned action was implemented by preventive maintenance to inspect and replace, if necessary, all components of the AVV control string that are susceptible to corrosion, prior to the next refueling outage. The generic implication to the ICS of this additional finding was recognized and preventive maintenance to periodically inspect and replace components, in the ICS control channels that are susceptible to corrosion, was implemented. During the eighth, ninth and tenth refueling outages, all the
'lCS modules were replaced with new or refurbished modules. This program replaced the
. original set of modules that were approximately 20 to 25 years old. By periodically monitoring the ICS with a Data Acquisition and Analysis System and trending data, the refurbished modules have been shown to be performing extremely well. The preventive maintenance approach, established in response to the generic implications of Action Plant 16,
- was to mplace a specific group of ICS modules on alternating refueling outages. Due to the excellent ICS performance since installing new or refurbished modules, the preventive maintenance approach is being modified from a periodic wholesale module replacement, to a
' situational approach based on trend data evaluation, visual inspections and ICS tuning results.
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