ST-HL-AE-2872, Special Rept:On 881027,standby Diesel Generator (Sdg) 13 Tripped When Released from Emergency Mode During Startup. Caused by Nonemergency Mode Shutdown Circuit.Instrumentation Connected to Shutdown Air Header & Restarted

Special Rept:On 881027,standby Diesel Generator (Sdg) 13 Tripped When Released from Emergency Mode During Startup. Caused by Nonemergency Mode Shutdown Circuit.Instrumentation Connected to Shutdown Air Header & Restarted

ML20195K052
Person / Time
Site:	South Texas
Issue date:	11/23/1988
From:	Vaughn G HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
ST-HL-AE-2872, NUDOCS 8812050122
Download: ML20195K052 (4)

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November 23, 1988 ST-HL-AE-2872 File No.: G02 U. S. Nuclear Regulatory Comrnission Attention: Document Control Desk Washington, DC 20555 South Texas Project Electric Generating Station Unit 1 Docket No. STN 50-498 Special Report Regarding A Diesel Generator Nonvalid Failure on October 27, 1988 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 a diesel generator nonvalid failure which occurred on October 27, 1988.

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

G.E. dQw '

G. E. Vaughn Vice President Nuclear Plant Operations GEV/BEM/n1

Attachment:

Special Report Regarding a Diesel Generator Nonvalid Failure on October 27, 1988 8012050122 881123 PDR S

ADOCK 05000493 f,h PDC I

NL 88.322.01 A Subsidiary of Ilouston Industries incorporated

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Ilouston,1.ighting & l'ower Company ST-HL-AE-2872 File No. G02 Page 2 l

Cet l Regional Administrator Region IV Rufus S. Scott Nuclear Regulatory Commission Associate General Counsel i 611 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power Company l Arlington, TX 76011 P. O. Box 1700 Houston, TX 77001 George D'ak, Project Manager U. S. Nuclear Regulatory Commission INFO Washington, DC 20555 Records Center 1100 circle 75 Parkway Jack E. Bess Atlanta, Ga. 30339-3064 Senior Resident Inspector / Operations e/o U. S. Nuclear Regulatory Commission Dr. Joseph H. Hendrie P. O. Box 910 50 Be11 port Lane Bay City, TX 77414 Be11 port, NY 11713 J. I. Tapia Senior Resident Inspector / Construction c/o U. S. Nuclear Regulatory Commission P. O. Box 910 Bay City. TX 77414 J. R. Newman, Esquire Newman & Holtzinger, P.C.

1615 L Street, N.V.

Washington, DC 20036 R. L. Range /R. P. Verret Central Power & Light Company i

P. O. Box 2121 l Corpus Christi, TX 78403 R. John Hiner (2 copies)

Chief Operating Officer I

City of Austin Electric Utility l 721 Barton Springs Road t

Austin, TX 78704 R. J. Costello/M. T. Hardt City Public Service Bo.rd P. O. Box 1771 San Antonio, TX 78296 Revised 08/24/88 NL.DIST

Ilouston,1.ighting & Pow;r unnpany Attachment ST-HL-AE-2872 Page 1 of 2 South Texas Project Electric Generating Station Unit 1 Docket No. STN 50-498 3pecial Report Regarding A Diesel Generator Nonvalid Failure on October 27 1988 Description of Event On October 27, 1988. Unit 1 was in'.iode 1 at 1001 power. Standby Dissel  ;

Generator (SDG) #11 was out of service lor maintenance. Technical Specification 3.8.1.1.b requires that ;he remaining two diesel generators be started within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to verif> thtar operability. At 2335 hours0.027 days <br />0.649 hours <br />0.00386 weeks <br />8.884675e-4 months <br />, SDG #13 was started to comply with the surve.11ance requirement. It attained rated speed and voltage within ten seconds as required. Approximately one minute later it tripped when released from the emergency mode. No alarms were present which would have indicated an emergency mode trip.

l Trouble shooting was performed to identify the source of the trip. Since ths "Master Trip Circuit" light was on at the local control panel, the trip was determined to have been caused by the non-emergency mode shutdown circuit.

Operations personnel conducted checks on engine systems and verified that there were no abnormal conditions present which could have caused the trip.

. Operations personnel did not indicate that any alarms were present prior to

! starting the diesel which would have resulted in a non-emergency mode shutdown. Instrumentation was connected to the shutdown air header and the engine was restarted. The engine continued to run when released from the emergency mode and no malfunctions of the shutdown controls were detected.

The instrumentation was removed and the diesel was started two more times. In

both cases, the diesel continued to run when released from the emergency mode.  !

The trouble shooting did not identify any specific cause of the non-emergency ,

mode shutdown.

r The operability test of SDG #13 was successfully performed on

] October 28, 1988 at 1922 hours0.0222 days <br />0.534 hours <br />0.00318 weeks <br />7.31321e-4 months <br /> and the diesel was declared operable at 2126 '

hours.

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lloustmgl.ighting & Power Company Attachment ST-HL-AE-2872 Page 2 of 2 ROOT CAU$E No specific root cause could be determined for this event. However, two potential causes were identified as follows:

1. A non-emergency mode trip was present which was not reset prior to starting the diesel. Interviews with operations personnel did not confirm the existence of any non-emergency mode trip.

2. A non-emergency mode trip spuriously operated while the diesel was in the emergency mode. Repeated attempts were made to re-create the trip conditions, however, the diesel continued to run when placed in the non-emergency mode.

ANALYSIS OF EVENT:

This failure occurred as a result of a trip which is not present during the emergency mode of operations. Per the criteria in Reg. Guide 1.108 this event is classif.'ed as a nonvalid failure. In the event of an actual challenge of the Standby Diesel Generator, it would have performed its safety function without tripping.

CORRECTIVE ACTION:

Subsequent to this occurrence, SDG #13 was started three times for troubleshooting and two times for surveillance testing. No non-valid failures occurred. Monitoring instrumentation did not detect any spurious control actuations. No further corrective action is planned.

ADDITIONAL INFORMATION:

Per the criteria of Reg. Guide 1.108, the failure described in this report has been classified as a nonvalid failure. As such, the test interval for SDG #13 remains 31 days. There have been twenty-six (26) valid tests performed on SDG #13 since the Unit 1 license became ef fective and, to date, no valid failures have occurred. This was the first nonvalid failure which could not be attributed to a specific trip or spurious actuation.

NL.88.322.01