ML19325C308

LER 89-021-00:on 890905,reactor Trip & Auxiliary Feedwater Sys Actuation Occurred.Caused by Defective Pump 22 Speed Controller Card Edge Connector.Defective Card Edge Connector Repaired & Card Frame Alignment checked.W/891005 Ltr

ML19325C308
Person / Time
Site:	South Texas
Issue date:	10/05/1989
From:	Ayala C, Chewning R HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-021, LER-89-21, ST-HL-AE-3250, NUDOCS 8910160050
Download: ML19325C308 (5)

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" The Light 4 g; Qg 1 Box 1700 .11ouston, Texas 77001- (713) 228-9211

' Houston Lighting & Power.__.,_.~..~._P.O.

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O: . October 05 1989 ST-HL-AE-3250

' File No.: G26

-10CFR50.73

'U.-S. Nuclear Regulatory Commission Attentions- Document Control Desk Washington,' DC .20555.

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South =. Texas- Project Electric Generating Station Unit 2 Docket No,' STN 50-499 Licensee Event Report 89-021 Regarding

< a Reactor Trip Due to a Defective Feedwater Pump Speed Controller Card Edge Connector Pursuant to 10CFR50.F3, Houston Lighting & Power-(HL&P) submits the attached Licensee Event Report.89-021 regarding a reactor trip due.to a defective feedwater pump speed controller card edge connector. This event did not.have any adverse impact on the health and safety of the public.

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

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. W. Chewning

- _ Q wM Vice President .

Nuclear Operations-

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Attachment:

LER-89-021, South Texas, Unit 2 R

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CCI Regional Administrator, Region IV Rufus S. Scott Nuclear Regulatory Commission Associate General Counsel

- 611 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power Company LArlington, TX 76011 P. O. Box 1700 -

. Houston, TX- 77001-George- Dick, Proj ect Manager U. S. Nuclear Regulatory Commission INPO

' Washington,;DC 20555 Records Center 1100 Circle 75 Parkway Jack E.-Bess Atlanta, GA 30339-3064 t ' Senior Resident Inspector-Unit I c/o U. S. Nuclear Regulatory Commission Dr. Joseph M. Hendrie  ?

P. O. Box 910 50 Be11 port Lane .

Bay City, TX. 77414 Be11 port, NY 11713 J. I. Tapia D. K. Lacker Senior Resident Inspector-Unit 2 Bureau of Radiation Control c/o U.'S. Nuclear Regulatory Commission Texas Department of Health P. O. Box 910 -1100 West 49th Street Bay City, TX 77414 Austin, TX 78756-3189 J. R. Newman, Esquire Newman & Holtzinger, P.C.

1615 L Street, N.W.

> Washington, DC 20036 R. L. Range /R. P. Verret Central Power & Light Company P. O. Box 2121-Corpus Christi, TX 78403 R.. John Miner (21 copies)

Chief Operating Officer City of Austin Electric Utility 721 Barton Springs Road

' Austin, TX 78704 R.~ J. Costello/M. T. Hardt-City Public Service' Board P. O. Box'1771 San Antonio, TX 78296 l

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'On September 5, 1989 Unit 2 was in Mode 1 at 100 percent power. At approximately 1607 hours0.0186 days <br />0.446 hours <br />0.00266 weeks <br />6.114635e-4 months <br />, control room operators obscrved speed oscillations l 'on the turbine driven Steam Generator Feedwater Pump (SGFP) 21. The operators l

attempted to regain speed control; however, the pump did not respond and subsequently tripped on overspeed. The resultant loss of steam generator level caused a reactor trip and auxiliary feedwater system actuation. No safety injection actuation occurred. The plant was stabilized in Mode 3. The cause of this event was a defective SGFP 21 speed controller card edge connector which was disturbed by a maintenance technician during 1 troubleshooting of a card associated with SGFP 22 in the same card frame. The defective connector was repaired, the card frame alignment checked, the p remaining printed circuit cards and edge connectors wore inspected and the L contact surfaces were cleaned. The printed circuit cards in the speed controller circuits on Unit I were also inspected and cleaned.

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-DESCRIPTION OF EVENT '

On September 5, 1989, Unit 2 was in Mode 1 at 100 percent power. At approximately 1607 hours0.0186 days <br />0.446 hours <br />0.00266 weeks <br />6.114635e-4 months <br />, control room operators observed speed oscillations-on the_ turbine driven Steam Generator Feedwater Pump (SGFP) 21. The operators attempted to' regain speed control however, the pump did not respond. In anticipation of a'feedwater pump trip, the operators began reducing turbine load and reactor power. .The pump subsequently tripped on overspeed. The resultant loss of steam generator level caused a reactor trip and auxiliary-feedwater actuation. .The reactor power at the time of the trip was 84 percent. The turbine tripped on the reactor trip and the feedwater isolation valves closed on low reactor coolant system average temperature. l f' '

Approximately'90 seconds following the reactor trip, the operators closed the main steam isolation valves to prevent excessive cooldown. No safety  ;

injection actuation occurred and the plant was stabilized in Mode 3. The NRC was notified pursuant to 10CFR50.72 at 1833 hours0.0212 days <br />0.509 hours <br />0.00303 weeks <br />6.974565e-4 months <br />.

Prior to this event, SGFP 22 had exhibited erratic speed control. The' speed control circuitry for all three SGFP's is housed in a common card frame, b While technicians were troubleshooting the speed control problem, they removed -

L _one of.the printed circuit cards for SGFP 22. During the card removal, a i; defective edge connector on a circuit card associated with SGFP 21 caused erratic speed controller output and the erratic pump behavior observed by the operators._ Due to the design of the control circuit, loss of continuity of the-speed demand signal caused the controller to drive the SGFP governor valves.open resulting in en overspeed trip. During post-trip troubleshooting, the effects.of disturbances of the card frame on SGFP 21 speed controller output was verified.

The~ defective card edge connector _was repaired, the card frame alignment checked, the remaining printed circuit cards and edge connectors were inspected and the contact eurfaces were cleaned. No other defective edge l connectors were found._ Following these repairs, the erratic controller card behavior could not be duplicated. Unit 2 was restarted on September 6, 1989 at 0454 hours0.00525 days <br />0.126 hours <br />7.506614e-4 weeks <br />1.72747e-4 months <br />.

CAUSE OF EVENT:

The cause of this event was a defective SGFP speed controller card edge i

connector which was unknowingly disturbed during troubleshooting of a circuit card for a differential SGFP in the same card frame. This resulted in the SGFP 21 trip.

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W ANALYSIS'OF EVENT:

-Reactor trip and Engineered Safety Features actuation is reportable-

-pursuant to 10CFR50.73(a)(2)(iv). The plant was brought to a stable shutdown in Mode 3 with no. unexpected post-trip transients. No safety injection actuation occured as'a result of this event.

CORRECTIVE' ACTION:

The following actions have been taken:

1. 'The defective Unit 2 card edge connector was repaired, the card frame alignment checked, and remaining printed circuit cards and E

edge connectors'were inspected and contact surfaces cleaned.

2. As a' result of this event, the Unit 1 SGFP speed control circuits have been inspected for defective card edge connections and their contact surfaces have been cleaned. No other card edge connector defects were found. ,

!- ADDITIONAL INFORMATION:

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- There have been no previous events reported regarding reactor trips due l

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to_ defective printed circuit card edge connectors.

A study has been initiated to address reliability of the secondary plant in response to-the recent Unit 2 trips. This review will include the SGFP

control system.

p The defective card edge connector was located in an Electro Hydraulic l: Controller manufactured-by Westinghouse. The card edge connector is style l< number 393A821003 as shown on Westinghouse bulletin I.L.1150-789. -

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