ST-HL-AE-3219, Special Rept:On 890805 & 07,two Diesel Generator Nonvalid Failures Occurred.Caused by Setpoint Drift of Jacket Water Temp Valve.Temp Valve Calibrated & Standby Diesel Generator 12 Satisfactorily Tested on 890815

Special Rept:On 890805 & 07,two Diesel Generator Nonvalid Failures Occurred.Caused by Setpoint Drift of Jacket Water Temp Valve.Temp Valve Calibrated & Standby Diesel Generator 12 Satisfactorily Tested on 890815

ML20247C286
Person / Time
Site:	South Texas
Issue date:	09/05/1989
From:	Chewning R HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-3219, NUDOCS 8909130306
Download: ML20247C286 (3)

Text

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The Light

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company P.O. Box 1700 11ouston, 'lexas 77001 (713) 223 9211 Houston Lighting #c Power - - . , . ~ ~ ~ - .. -- --.- - -.----- - -

September 5, 1989 ST-HL- AE-3219 File No.: G02.

U. S. Nuclear Regulatory Commission.

Attention: Document Control Desk Washington, DC 20555 South Texas Project Electric Generating Station Unit 1 Docket No. STN 50-498 Special Report Regarding Two Diesel Generator Nonvalid Failures on Aurust 5 and 7. 1989 Pursuant to the South Texas Project Electric Generating Station Technical Specifications 4.8.1.1.3 and 6.9.2, Houston Lighting & Power submits the attached Special Report regarding two diesel generator nonvalid failures which occurred on August 5 and 7, 1989.

If you should have any questions on this matter, please contact Mr. C. A. Ayala at (512) 972-8628.

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R. W. Chewning /

Vice President [/

Nuclear Operations V RWC/BEM/nl

Attachment:

Special Report Regarding Two Diesel Generator Nonvalid Failures on August 5 and 7, 1989 l

Al/046.NL5 A Subsidiary of liouston Industries Incorporated If 8909130306 890905 PDR ADOCK 05000498 (

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,y, s-4 Attachment ST-HL-AE-3219

< Page 1 of 2 South Texas- Project Electric Generating Station Unit 1 Docketlio. STN 50-498 Special R port Regarding Two Diesel Generator Nonvalid Failures on August 5 and 7: 1989 Description of Occurrence:

On' August.5, 1989, Unit I was in Mode 5 for refueling. outages, ~ Standby Diesel Generator (SDG) 12 was started and loaded for approximately one hour to satisfy surveillance test requirements. During the cooldown cycle following the test, the engine tripped at 0657 horn a. A." Jacket Water High Temperature" alarm was' received at the time of the tr'.p. This trip is active only in the

'non-emergency mode. The jacket water temperature was determined to be approximately 170"F which is well below the trip setpoint of 205 F, No work request was prepared to. investigate and correct this condition due to a

m. miscommunication between'the Shift Supervisor and the Reactor Operator. Each believed that the other operator had initiated the document.

'On August'7, 1989, SDG 12 was started to perform engine analysis prior to the 18 month inspection. It ran loaded for approximately 40 minutes and tripped at'1112 hours0.0129 days <br />0.309 hours <br />0.00184 weeks <br />4.23116e-4 months <br />. The-" Jacket Water High Temperature" alarm was again present following the trip. The jacket water temperature was. determined to be approximately 170'F. The engine was started for troubleshooting. .The jacket water temperature valve, which monitors jacket water temperature and initiates a non-emergency trip on high. temperature, was observed to be tripped with the engine at normal operating temperature. The valve was removed and its calibration checked. It was . found to trip at 164.7 F. The setpoint for this valve is 205 F.

Subsequent investigation revealed that the valve had not been included in the preventive maintenance program and was not subject to periodic calibration checks. Applicability of the preventive maintenance' program to-the temperature valve which actuates a non-emergency mode trip only is under review.

Cause of Event:

The cause of this event was setpoint drift of the jacket water temperature valve. This valve was not included in the preventive maintenance program.

A1/046.NL5

Attachment ST-HL-AE-3219 Page 2 of 2 Analysis of Event:

The failures described in this report were the result of a trip which is bypassed in the emergency mode. Per the criteria in Regulatory Guide 1.108, these failures are classified as non-valid. In the event of an actual challenge of the SDG, it would have performed its safety function withour tripping.

Corrective Actions:

The following corrective actions are being taken as a result of this event:

1. The temperature valve was calibrated and SDG 12 was satisfactorily tested on August 15, 1989.

2. The temperature valves on the remaining diesel generators on both units will be re-calibrated during scheduled train outages by November 25, 1989.

3. A review will be performed of diesel generator trip instrumentation to ensure that the correct preventive maintenance activities have been specified. This action will be completed by September 30, 1989.

4. The Shift Supervisor and Reactor Operator who failed to prepare the work request following the August 5, 1989 event have been cou.tseled l by the Unit 1 Operations Manager regarding the need to ensure that work documents are prepared to disposition diesel generator problems.

Additional Information:

There have been 39 valid tests performed on SDG 12 since completion of the diesel generator reliability demonstration, with one valid failure.

Therefore, the test interval remains 31 days.

Al/046.NL5 1

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