ML20101L299

Special Rept 1-SR-92-001-00:on 920528,engine Trip Occurred Due to Apparent High Vibration at Engine Rear Vibration Sensor.Caused by Low Lube Oil Pressure.Sensor & Related Components Replaced

ML20101L299
Person / Time
Site:	Comanche Peak
Issue date:	06/29/1992
From:	William Cahill TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1-SR-92-001-00, 1-SR-92-1, TXX-92304, NUDOCS 9207070061
Download: ML20101L299 (4)

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~~~ m 3 g Log # TXX-92304 File # 10250 71/ELEC7R/C Ref. # 10CFR50.36(c)(5)

June 29, 1992 Wlutam J. Cahill, Jr.

Grny Yke Presurno U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)

DOCKET NO. 50-445 EMERGENCY DIESEL GENERATOR START AND LOAD-RUN EVENTS DURING SURVEILLANCE TESTING SPECIAL REPORT NO. 1-SR-92-001-00 Gentlemen:

Enclosed is a 30 day special report submitted in accordance with CPSES Unit-1 Technical Specification 4.8.1.1.3, " Electrical Power Supply A. C.

Sources".

Sincerely,

'd et William J. "Cahill, Jr.

-JET /tg c- R. D. Martin, Region IV T. A. Bergman, NRR Resident Inspectors, CPSES (2) l l

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-Enclosure _to TXX 92304 Page 1 of 3

. TU Electric Comanche Peak Steam Electric Station, Unit 1 Special Report No. 1-SR-92-001-00

-Emergency Diesel Generator Start and Load-Run Events During Surveillance Testing 1.0 Report Requirement This Special Report'is submitted in accordance with Comanche Peak Steam -Electric Station (CPSES) Unit 1 Technical Specification 4.8.1.1.3, " Electrical Power Supply A.C.

Sources". Specification 4.8.1.1.3 requires that all Diesel Generator f ailures, - valid or invalid, be reported to the commission in a Special Report pursuant to Technical Specification 6.9.2 within 30 days.

2.0 Event Description On Mey 28, 1992, at approximately 1005 CDT, Train B Emergency Diesel Generator (EDG) 1-02 (Component Tag Number CP-MEDGEE-

02) _ was_ manually started trom the Control Room by Operations personnel for performance of the monthly surveillance test in accordance with Technical Specification 4.8.1.1.2. Shortly after closure of the diesel generator breaker, an engine trip occurred due to apparent high vibration at the engine rear vibration sensor. Troubleshooting revealed vibration sensor failure, and the component.was replaced.

At approximately 1718, a second start was attempted to allow calibration of the newly installed- vibration sensor.

Approximately- one minute into the run, the_ engine tripped on low lube oil pressure. Subsequent troubleshooting revealed

the_cause of- the . second - trip to be a malfunction lube oil pressure switch. The pressure switch was replaced, and EDG 1-02 was prepared for a third run.

On_May 29, 1992, at approximately 0815, a-third run attempt was made to calibrate the vibration sensor and to perform the-monthly Technical Specification surveillance test on EDG 1-02.

The test was successfully completed with the EDG achieving the design rated speed, frequency, and voltage within the specified time limit, and carrying the prescribed load for_the

, required _ time. Following completion of the test run, with the EDG unloaded and disconnected from the bus,-a spurious engine shutdown-terminated the run.

Enclosure to TXX 92304 Page 2 of 3 Special Report No'. 1-SR-92-001-00 4 Emergency Diesel Generator Start and Load-Run Events During Surveillance Testing Extensive investigation revealed a shutdown rather than the occurrence of a protective trip, Emergency and normal (bypassed in emergency mode) trips were- verified not to be involved. Additional investigation performed with the control circuitry deenergized, focused on various control circuit elements. No switches 'were found out of position, and no problems were found with the related wires, terminations, or contacts. The pneumatic logic was-inspected, and no abnormal conditions such as venting or leaks were found. The engine was restarted with all trips active, and the related portion of the test procedure was repeated with additional operating and engineering personnel observing. No abnormalities were observed. Verification of the absence of personnel error was inconclusive.

3.0 Corrective Actions Failure trending will determine an appropriate replacement schedule to minimize the- potential for age-related sensor degradation. Future EDG runs will be monitored for abnormalities within the circuits functioning to shut down the engine.

1 L 4.0 Evaluation Results The- two engine- trips experienced on May 28 have been definitely attributed te spurious operation of trips that are

-bypassed in the emergency operating mode. The conditions l- leading to those trips would not have resulted in the failure of the diesel generator unit to start, accelerate and load during a response - to an actual emergency start- signal.

Consistent with the guidance of regulatory position C.2.e of Regulatory Guide 1.108, the two trips are not considered' valid

' tests or failures.

The engine shutdown following successful completion of-the j start and' run test on May 29 did-not involve the failure of the EDG to start, accelerate, and assume the design-rated load, within and for the time _ prescribed, during an emergency or a valid test. Subsequent review .of the trip and shutdown circuits did not reveal a condition which would have resulted in t5e f ailure of the diesel generator unit to start, accelerate, and load during a' response to an actual emergency start signal. The event is not considered a valid, invalid, or nonvalid failure.

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Enclosure to TXX 92304 Page 3 of 3

. Special Report No. 1-SR-92-001-00

- Emergency Diesel Generat r Start and Load-Run Events During Surveillance Testing on day 28 and 29, EDG 1-02 was unavailable (unable to respond to a valid emergency start signal) during two separate periods totaling 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> and 8 minutes. The current test interval requires that the unit be demonstrated operable at least once per 31 days by verifying that the unit starts from ambient conditions and achieves design rated speed, frequency, and voltage within the specified time limit. The current test interval is in conformance with the schedule of Regulatory Position C.2.d of Regulatory Guide 1.108.

The lack of clarity in Regulatory Guide 1.108 has resulted in continued confusion regarding the reporting requirements related to EDG start and load-run events. Therefore, this report is being submitted although the events described are not considered reportable when evaluated against Regulatory Position C.2.e of Regulatory Guide 1.108.

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