ML20063J544

Special Rept 94-01:on 940113 & 0210,EDG D Load Failures Occurred Due to Inadequate Lubrication of Fuel Racks & Fluctuations in Output of Relay Which Selects Control Signal to Engine Governor,Respectively.Fuel Racks Lubricated

ML20063J544
Person / Time
Site:	Hope Creek
Issue date:	02/11/1994
From:	Hovey R Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
94-01, 94-1, NUDOCS 9402240024
Download: ML20063J544 (3)

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. h Je ev i EOP Hope Cnw Genereng Staban February 11, 1994 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

Hope Creek Generating Station Docket No. 50-354 Unit No. 1 Special Report 94-01 This Special Report is being submitted pursuant to the requirements of Hope Creek Technical Specification 4.8.1.1.3, due to a "D" EDG Load Failure on 1/13/94 and 2/10/94.

On January 13, 1994, during performance of the "D" Emergency Diesel Generator (EDG) monthly surveillance test, the generator experienced fluctuations in kilowatt (kw) output of approximately 1000 kw when synchronized and loaded to 3000 kw. Operations personnel monitoring the diesel run reduced load to minimum, and removed the unit from the grid. It was suspected that the load fluctuations were being caused by binding of the fuel racks due to inadequate lubrication.

Personnel present at the time of the test failure stated the racks felt dry to the touch. The fuel racks were lubricated two days prior to the event, however, between the lubrication and test run a wipe down of the diesels was performed in accordance with station housekeeping requirement and it was suspected that the wipe down may have removed the lubricant.

After discussion with the personnel involved in the ,

housekeeping work it was determined the racks were not wiped down. The racks were again lubed, the engine and generator controls were instrumented and the diesel generator was run satisfactorily. The diesels were instrumented to determine if any deficiencies existed in the governor or generator control circuits which could have caused the output fluctuations. The subsequent loading and one hour run was conducted without any observed fluctuations. System Engineering and Operations personnel evaluated the diesel performance following the fuel rack lubrication and along with the satisfactory surveillance results declared the diesel generator operable. The run did not provide any evidence of a malfunction in the control circuitu.

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The three redundant diesel generators were run in accordance

, with Tech Spec 3.8.1.1 (ACTION b) after verification that the fuel racks were properly lubricated. Data taken during these runs were used to compare the performance of the "D" diesel j control signals with the remaining three operable diesels to ,

determine if any discrepancies existed between the control circuits. No fluctuations were observed in the three EDG's outputs and the data collected did not indicate any '

differences existed between the four diesels.

"D" EDG was again run on 1/14/94 to determine if any additional abnormal conditions, identified through a review of nuclear network items and discussions with the vendor, could have existed. The test results again did not identify any abnormal conditions in the control circuits or diesel generator output fluctuations.

The most probable root cause of the event'had been identified as inadequate lubrication of the fuel racks, but additional monitoring was scheduled for the next regular surveillance run to confirm the original root cause under similar conditions where the diesel has been shutdown for a similar duration (approx 30 days).

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On 2/10/94, the "D" diesel was again instrumented and run in accordance with the monthly surveillance test. The initial start and loading proceeded normally. Approximately 25 minutes into the run the DG output began to swing as previously experienced. After several attempts to manually stabilize generator output were unsuccessful the DG was shutdown and declared inoperable.

Engineering personnel monitoring the test reviewed test data obtained and found fluctuations in the output of a relay  :

which selects the control signal to the engine governor.

There are two modes of operation for the DG, droop mode for running in test while synchronized to the grid, and isochronous mode when the DG is running under emergency conditions connected only to its respective 4.16 kV bus. The  ;

failure appears to be isolated to-the relay contacts associated with the droop (test mode) portion of the circuit, ,

indicating the DG was capable of performing its intended i function under accident conditions. The isochronous mode controls generator output. based on generator frequency, typically 60 cycles. If the generator is connected to the  ;

grid, where the frequency may be less than 60 cycles, and  ;

j switched to isochronous the generator would attempt to ,

l increase speed and load to maintain 60 cycles. This is consistent with the observations of control room personnel monitoring generator output. Additional testing of the relay I is underway to determine the root cause of the relay failure

• and additional corrective actions which may be required.

Interim actions to replace the failed relay have been completed and the "D" DG has been tested satisfactorily.

This report is being submitted at this time to comply with I

the 30 day report requirement due to the initial failure. A  ;

follow-up report will be submitted as soon as the additional testing of the failed relay is completed.

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~The initial test failure (test no.138) for "D" EDG in the last 100 tests.

was the third failure The two previous failures I

were attributed to operator error in that the governor control setting was not set correctly prior to initiating the diesel start and subsequent loading. The test frequency is also being reviewed and will be updated to cover the second  ;

failure in the follow-up report.

The EDG Reliability data base was reviewed to verify that the ,

test interval cited above is in conformance with the. schedule of Regulatory Position C.2.d, Regulatory Guide 1.08. There have been a total of 168 load demands with an additional 8 start demands since the last failure. The surveillance test ,

interval will remain at 31 days as set forth in Tech Specs i Table 4.8.1.1.2-1, pending a new review including the second failure. l Sincerely, R.J. Hovdy General Manager -

Hope Creek Operations LLA/

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