ML20207K810
| ML20207K810 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 10/10/1988 |
| From: | Fitzpatrick E GENERAL PUBLIC UTILITIES CORP. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8810170037 | |
| Download: ML20207K810 (3) | |
Text
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ENuclear t,2":ar-Route 9 South Forked River, New Jersey 087310388 609 971-4000 Writer's Direct Dial Number:
October 10, 1988 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Station Pl-137 Washington, DC 20555
Dear Sir:
Subject:
Oyster Creek Nuclear Generating Station Docket No. 50-219 Isolation Condensers and Emergency Diesel Generators On September 26, 1988, following a surveillance test of the
'A' Isolation Condenser, it was observed that its shell temperature was increasing which ultimately resulted in steaming of the Isolation Condenser to the atmosphere. Following this event, General Public Utilities Nuclear Corporation (GPUN) initiated an investigation in order to determine the cause of this steaming and also to review the evaluation of the 'B' Isolation Condenser which had been steaming previously.
When the 'B' Isolation Condenser had begun steaming, the cause was attributed to leakage through the condensate return valve. After 'A' Isolation Condenser began steaming following the surveillance test, GPUN became concerned that the cause of both occurrences may not have been fully understood.
GPUN established a dedicated evaluation team of Plant Engineering and Technical Functions personnel to perform a detailed review of the Isolation Condenser system and the circu.astances leading to steaming.
After a few days, the team determined there was a high probability that the steam lines to the Isolation Condensers contained a significant volume of water.
Station management, in response co a recommendation from the evaluation team, directed that the isolation condensers be isolated and a plant shutdown be initiated in accordance with the Oyster Creek Technical Specifications.
This action was taken due to the industry experience with water hamer events in Isolation Conderser steam lines.
Water hammer in these lines has the potential te cause significant damage to the system.
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GPU Nuclear Corporation is a subsid'ary of the General Pubhc Utiht.es Corporation
Following reactor shutdown, GPUN commenced the cycle 12 refueling outage and developed a formal plan under the direction of a project manager to address the issues related to the events which have occurred on 'A' and 'B' Isolation Condensers since restart from the last outage.
The plan includes:
(1) Development of a thermohydraulic model to assist in the analysis.
(2) Reconstruction of a detailed sequence of events.
(3) A stress analysis of system piping and equipment nozzles.
(4) An evaluation and modification, if necessary, of procedures in order to prevent recurrence, identify the onset of abnormal flow conditions, and to recover should abnormal flow conditions occur.
(5) A determination of those modifications, if warranted, that prevent or minimize abnormal flow conditions and/ce that monitor the onset of such conditions.
(6) A review of industry experience as well as maintenance and test activities.
Also following reactor shutdown, an event occurred on October 2,1988 in which power to the 'D' 4160 volt emergency bus was lost while being powered from the startup transformer.
An investigation revealed that the cables from the emergency diesel generator had degraded placing a fault condition on the bus. GPUN is reviewing this occurrence and the circumstances surrounding this event to determine the root cause and any necessary long term corrective actions in conjunction with replacing the faulted cables.
The NRC has established an Augmented Inspection Team (AIT) to review the events associated with the Isolation Condensers and the loss of the
'D' emergency bus.
GPUN and the NRC AIT have exchanged information regarding these events and the above GPUN actions which are being taken to address the identified issues.
This has proven beneficial in assuring an in-depth review of the events and proper identification of the issues.
GPUN will complete any necessary actions required prior to restart from the 12R refueling outage to assure the Isolation Condensers and Diesel Generators are fully capable of performing their design function.
GPUN will continue to advise the NRC inspection personnel of those actions in progress and the results achieved following completion of the identified reviews.
Final reports providing the results of the GPUN evaluation and the conclusions reached will be developed.
These reports will be provided to the NRC and outstanding issues resolved prior to restart from the 12R refueling outage.
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e Should you have any questions or comments, please contact Mr. George W. Busch at (609) 971-4909.
Very truly yours, W
L E. E. Fitzp ck Vice President and Director Oyster Creek EEF/GB/smz (0144A:20) cc: Mr. William T. Russell, Administrator Region I U.S. Nuclear Regulatory Comission 475 Allendale Road King of Prussia, PA 19406 Mr. Alexander W. Dromerick, Project Manager U.S. Nuclear Regulatory Comission Division of Reactor Projects I/II Washington, DC 20555 flRC Resident Inspector Oyster Creek Nuclear Generating Station Forked River, flJ 08731 1
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