ML19332C866

LER 89-027-00:on 891025,discovered That Closed Limit Switch on Main Turbine Throttle Valve 2 Disconnected.Caused by Failure of Limit Switch Linkage.Review to Be Performed of Limit Switch Linkage design.W/891122 Ltr

ML19332C866
Person / Time
Site:	South Texas
Issue date:	11/21/1989
From:	Ayala C, Chewning R HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-027, LER-89-27, ST-HL-AE-3303, NUDOCS 8911290105
Download: ML19332C866 (5)

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s I'.O. Box 1700 llouston, Texas 77001 (713) 228 9211 Houston Lighting & Power.- .~~_

November 22, 1989 ST-HL-AE-3303

< File No.: G26

! 10CFR50.73 i.

I U. S. Nuclear Regulatory Commission Attention: Document Control Desk

f. Washington, DC 20555 South Texas Project Electric Generating Station Unit 2 Docket No. STN 50-498 Licensee Event Report 89-027 Regarding An Inoperable Turbine Throttle Valve L!mit Switch Resulting in a Technical Specification Violation L

Pursuant to 10CTR50.73. Houston Lighting & Power (HL&P) submits the attached Licensee Event Report 89-027 regarding an inoperable turbine throttle valve limit switch which resulted in a Technical Specification violation.

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 Vice President Nuclear Operations RWC/BEM/n1

Attachment:

LER 89-027, South Texas, Unit 2 t

T 8911290105 89112g jDR ADuc:: osooo49, PDC

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. Hougon Lighting & Pown Company ST HL AE 3303

' South Texas Project Electric Generating Station File No. : C26 Page 2 j CC*

u' Regional Administrator, Region IV Rufus S. Scott ,

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' Nuclear Regulatory Commission - Associate General Counsel

011 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power Corpany Arlington, TX 76011 P. O. Box 1700 '

' Houston, TX 77001 George Dick, Project Manager U.S. Nuclear Regulatory Commission INPO

, Washington, DC 20555 " Records Center

'J. I. Tapia -

1100 circle 75 Parkway I Atlanta, CA 30339 3064 Senior Resident Inspector .

c/o U. S. Nuclear Regulatory Dr. Joseph M. Hendrie-  !

Commission 50 Be11 port Lane P.:0. Box 910 Be11 port, NY 11713 i

Bay City, TX 77414:  :

D. K. Lacker J. R. Newman, Esquire Bureau of Radiation Control Newman & Holtzinger, P.C. Texas Department of Health 1615 L Street, N.W. 1100 West 49th Street

' Washington, DC 20036 Austin, TX 78704  !

R. L. Range /R. P. Verret Central Power & Light Company f P, 0. Box 2121 i

Corpus Christi, TX- 78403 t

J . : C. ; Lanier Director of Generations

. City of Austin Electric Utility [

. 721 Barton Springs Road  !

Austin,:TX 78704 ,

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

e Revised 11/15/89 r

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UCENSEE EVENT REPORT (LER) ' Na' $ ' ' '" l e ACILITY .eAest m DOCEti NutADE R 126 PAGE G South Texas Unit 2 o 15 l o t o I o l4 l 919 1 lor l0 p

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LICENatt CONT ACT FOR THIS LI A till NAME TELEPHONE NUMSER

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Charles Ayala - Supervising Licensing Engineer 51 2 9; 7,2, ,8,6 ,2l8 COMPLEf t DNE LINE 80h 4 ACM COMPONENT F AILURE DitCRIDED IN THIS REPORT 1131 CAUSt COMPONINT M AC- A 0RTA ,

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On October 25, 1989, Unit 2 was in Mode 1 at 100 percent power. At approximately 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />, a non-licensed Turbine Building Reactor Plant Operator discovered that the closed limit switch on Main Turbine Throttle Valve #2 was disconnected. He wrote a Work Request identifying the problem and placed it on the Unit Supervisor's desk. The Work Fequest was reviewed by a licensed operator at 1904 hours0.022 days <br />0.529 hours <br />0.00315 weeks <br />7.24472e-4 months <br />. The throttle tralve limit switch was l

declared inoperable and the Work Request was processed for immediate implementation. The limit switch was repaired and declared operable at 2110 hours0.0244 days <br />0.586 hours <br />0.00349 weeks <br />8.02855e-4 months <br />, approximately eight hours and ten minutes following its discovery.

With one turbine throttle valve input to the Reactor Trip System inoperable, Technical Specification 3.3.1 requires that the channel be tripped within six hours. The cause of this event was failure of the limit switch linkage.

The condition was not immediately corrected due to failure of the non-licensed operator to ensure that a licensed operator was aware of the conditien. Once i

the condition was reviewed by a licensed operator, action was taken to ensure that Technical Specific'tions were complied with. A review will be performed of the limit switch linkage design and enhancements wil) be implemented as j required. The need to promptly identify problems with safety-related or Technical Specification required equipment will be incorporated in non-licensed operator initial and requalification training.

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text v a== ausse e nesissa == sammew ame sein asna w nn DESCRIPTION OF EVENT:

On October 25, 1989, Unit 2 was in Mode 1 at 203 percent power. At approximately 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />, a non-licensed Turbine Building Reactor Plant i Operator discovered that the closed limit switch on Main Turbine Throttle Valve #2 was disconnected. He wrote a Work Request identifying the problem ,

and placed it on the Unit Supervisor's desk. The Work Request was reviewed by t a licensed operator at 1904 hours0.022 days <br />0.529 hours <br />0.00315 weeks <br />7.24472e-4 months <br />. The throttle valve limit switch was declared inoperable and the Work Request was processed for immediate implementation. The limit switch was repaired and declared operable at 2110 hours0.0244 days <br />0.586 hours <br />0.00349 weeks <br />8.02855e-4 months <br />, approximately eight hours and ten minutes following its discovery.

With one turbine throttle valve input to the Reactor Trip System inoperable, Technical Specification 3.3.1 requires that the channel be tripped within six hours. The NRC was notified of this operation prohibited by Technical s Specifications at 1248 hours0.0144 days <br />0.347 hours <br />0.00206 weeks <br />4.74864e-4 months <br /> on October 26, 1989.

CAUSE OF EVENT:

The cause of this event was failure of the turbine throttle valve limit ,

switch linkage. Technical Specification required actions were not immediately taken upon discovery of the inoperable limit switch due to failure of the non- ,

licensed coerator to ensure that a licensed operator was aware of the condition. Once the condition was reviewed by a licensed operator, action was taken to ensure that Technical Specifications were complied with.

ANALYSIS OF EVENT:

The turbine throttle valve limit switches provide inputs to the Reactor Trip System to initiate a reactor trip on a turbine trip above 50 percent

• power. The minimum channels required to initiate a trip is two. Throughout

. this event, three channels were operable.

Non-licensed Reactor Plant Operators perform monitoring functions and l operate equipment in the secondary plant. The nature of their duties does not l require an understanding of Technical Specification requirements. The Reactor l

Plant Operator who discovered the disconnected limit switch took the proper L action of preparing a Work Request and submitting it to the Control Room.

l However, since he did not know that the limit switch was affected by Technical l Specifications, he did not take action to ensure that the Work Request was reviewed by a licensed operator immediately. Once the condition was reviewed by a licensed operator, action was taken to ensure that Technical Specifications were complied with. Since this condition was known to exist in excess of six hours without being corrected or without tripping the channel, it represents operation prohibited by Technical Specification 3.3.1 which is reportable pursuant to 10CFR50.73(a)(2)(1)(B).

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, CORRECTIVE ACTIONS f The following corrective actions are being taken as a result of this event  ;

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1. The design of the turbine throttle valve limit switch linkage is being reviewed for possible enhancements to prevent future failures. This '

, review will be completed by December 20, 1989. If enhancements are ,

required, they will be scheduled for implementation at that time.

2. A memorandum has been issued to non-licensed operators regarding the need ,

to identify any problems with safety-related equipment to a licensed operator immediately. The method to identify safety-related equipment has alno been specified.

3. A discussion of this event and the need to promptly identify problems with safety-related or Technical Specification controlled equipment will be incorporated into the next program of non-licensed operator initial training and into requalification training for non-licensed operators by March 15, 1990.

AD3ITIONAL INFORMATION:

There have been no previous events reported regarding f ailure of the turbine .

throttle valve limit switch linkage.

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