ST-HL-AE-3801, Special Rept:On 910117,SDG 12 non-valid Failure Occurred. Caused by Unstable Relay Contact Resistance Due to Oxidation.Relays 3/4X1,9/3UP & 10/4EX3 Replaced & Procedure Governing Classification of Sdg Starts Will Be Revised

Special Rept:On 910117,SDG 12 non-valid Failure Occurred. Caused by Unstable Relay Contact Resistance Due to Oxidation.Relays 3/4X1,9/3UP & 10/4EX3 Replaced & Procedure Governing Classification of Sdg Starts Will Be Revised

ML20081M782
Person / Time
Site:	South Texas
Issue date:	07/01/1991
From:	Jump W HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-3801, NUDOCS 9107100116
Download: ML20081M782 (5)

Text

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The Light c o mp a ny ut h Tesu Projnt F.lutric Generating Station P.O.Bos289 Wadsworth, Tetu 77483 llouston Lighting & Pown July 1, 1991 ST-llL AE-3801 File No.: CO2 10CFR50.36(c)(5)

U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Electric Generating Station Unit 1 l Docket No. STN 50-498 l Special Report Regarding Standby Diesel Generator 12 ,

Non-Valid Failure on January 17. 1991  ;

Pursuant to the South Texas Project Electric Generating Station (STPEGS)

Technical Specifications 4.8.1.1.3 and 6.9.2, Houston Lighting & Power submits ,

the attached Special Report regarding a Standby Diesel Generator (SDG) non-valid failure which occurred on January 17, 1991.

If you should have any questions on this matter, please contact Mr. C. A. Ayala at (512) 972-8628 or myself at (512) 972-8350, b .p % f William J . Ji.ap Manager, Nuclear Licensing MKJ/sgs

Attachment:

Special Report Regarding a SDG Non-Valid Failure on January 17, 1991 8**"81'3"*001 A Subsidiary of flouston Industries in:orporated / [

9107100116 910701 l \

PDR ADOCK 05000498

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ST HL AE. 3801 llouston Light.ing & Pswer Compan)

File No. : CO2 South Texas Project Electric Generat ng Stat.wn p,g, y cc:-

' Regional-Administrator, Region IV Rufus S. Scott Nuclear Regulatory Commission Associate General Counsel 611 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power Company Arlington, TX- 76011 -

P. O. Box 61867 llouston, TX 77208 George Dick, Project Manager U.S. Nuclear Regulatory Commission INPO Washington, DC 20555 Records Center 1100 Circle 75 Parkway J. I. Tapia Atlanta, CA 30339-3064 Senior Resident Inspector

c/o U. S. Nuclear Regulatory Dr. Joseph M. Hendrie Commission 50 Be11 port Lane P. O. Box 910 Bellport, NY 11713 Bay City, TX -77414 D. K. Lacker l 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 78756 3189

-D. E. Ward /T, M. Puckett Central Power and Light Company P. O. Box 2121 Corpus Christi, TX 78403 J. C. Lanier/M. B. Lee City of Austin Electric Utility Lepartment P.O. Box 1088 Austin, TX 78767 R. J. Costello/M. T. Hardt City.Public Service Board P. O. Box 1771-San Antonio, TX 78296 L

Revised 01/29/91 L4/NRC/

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4 Attachment ST HL AE 3801 Page 1 of 3 South Texas Project Electric Generating Station Unit 1 Docket No. STN $0 498 Special Report Regarding Ltandby Diesel Generator 12 Non-Valid Failure on January 17. 1991 2_ESCRIPTION OF EVENT:

On January 17, 1991, Unit I was in mode 6 during a refueling outase. At approximately 1915, Standby Diesel Generator (SDG) 12 was started in the emergency mode to perform the monthly Technical Specification surveillance test. After release from the emergency mode, the SDG was paralleled to the Engineered Safety Features (ESP) bus. While attempting to load the SDG, load indications unexpectedly increased to approximately 2000 KW. The operator tried to decrease the load however, load indications continued to increase to approximately 4000 KW and then dropped to 0 KW. The output breaker opened and the SDG tripped on reverse power. This trip was classified as a nonvalid failure and logged in the SDG Start Log. However, no Special Report was generated reporting thia trip in accordance with Technical Specification section 4.8.1.1.3.

Troubleshooting was conducted that identified unstable contact resistance on relays associated with the governor control system due to oxidation of the relay contacts. Unstable contact resistance would delay SDG response to operator adjustments made through the governor control system. Relays 9/3UP, 10/4EX3 and 3/4X1 were replaced. The relays replaced as a result of this nonvalid failure were Agastat GPDR relays. Improper operation of the relays due to age related factors was previously discussed in a Special Report submitted in response to nonvalid failures on SDG 12 on August 29, 1990. That Special Report committed to replacement of all Glass 1E and non-1E relays in the Unit 1 SDGs. This was completed during the Spring 1991 refueling outage for Unit 1 (after this event) and included the relays identified in this report. The SDG was tested and placed back into service on January 18 at 1600.

Failure to report the January 17th incident in accordance with Technical Specification requirements was identified on May 23, 1991 during a review of the SDG Start Log by the system engineer. The review was conducted to verify that all reportable events had been properly addressed and was conducted in conjunction with a task force effort assigned to evaluate SDG work history information. The plant procedure Eoverning classification of SDG starts provideo guidance on processing nonvalid failures. The procedure requires that a Station Problem Report (SPR) or Work Request (WR) be generated by the Shift Supervisor or designee for each valid or noavalid failure. Completion of this action is indicated by the Shif t Supervisor's initials in the SDG Start Log. A WR was generated for this incident although an SPR was not. The work request process requires that each WR be evaluated to determine whether a SPR is necessary by the WR issuing authority (the Shift Supervisor, in this SREP\91-165.001

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Attachreent ST.HL AE-3801 Page 2 of 3 South Texas Project Electric Generating Station Unit 1 Docket No. STN 50-498 Special Report Regarding Standby Diesel Generator 12 Non-Valid Failure on January 17. 1991 DESCRIPTION OF EVENT: .(cont'd) case). The WR issued to troubleshoot this trip indicated that no SPR was 1 necessary. The SPR procedure requires a reportability review, including Technical Specification Special Reports, and initiates plant actions which assure reporting requirements are implemented. The procedure also requires a weekly review ~of the SDG Start Log by the system engineer. The system engineer is also responsible for notifying Licensing of reporting requirements arising.from valid and nonvalid failures. The SDG Start Log entry for January 17 designates the start as a nonvalid failure and is initialed by both the Shift Supervisor and system engineer. The log does not provide a mechan'sm for indicating what action was taken to address the valid or nonvalid failure reporting requirement.

CAUSE OF EVENT:

The apparent cause of this nonvalid failure is attributed to unstable relay contact resistance due to oxidation. The causes of the failure to report this incident were inadequate procedural instructions and inadequate tracking mechanisms in place to track resolution of test failures.

ANALYSIS OF EVENT:

This incident is classified as a nonvalid failure since SDC 12 operated satisfactorily in the emergency mode and if challenged would have performed its safety function. Although failure to submit a special report within 30 days is a violation of Technical Specification 4.8.1.1.3, it did not result in plant operation prohibited by a Technical Specification. Failure to submit a report is an administrative error that'did not affect safe operation of the plant- .

GQRRECTIVE ACTIONS:

1. Relays 3/4X1, 9/3UP and 10/4EX3 were replaced.

2. -The-procedure governing classification of SDG starts will be revised to require that an=SPR be generated in addition to a WR for valid and nonvalid failures. The SDG Start Log will also be revised to include a column'for entry of the WR and SPR number generated to address the failure. This action will be completed by September 1, 1991.

SREP)91-165.001

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• Attachment ST ilL-AE 3801 Page 3 of 3 South Texas Project Electric Cenerating Station Unit 1 Docket No. STN 50 498 Special Report Regarding Standby Diesel Generator 12 Non-Valid Failure on January 17. 1991 ADDITIONAL INFORMATION:

Per STPECS Technical Specification 4.8.1.1, there have been no valid failures in the last 20 valid tests of SDG 12 and the number of valid failures in the last 100 valid tests is less than four, therefore, the testing frequency for SDG 12 remains at once per 31 days. The testing frequency for SDG 12 was -

L evaluated by the system engineer st- the time of this nonvalid failure and remained unchanged from once per 31 days.

This is the only occurrence of an SDG reportable failure that was not reported in a Special Report within Technical Specification time limits.

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l-1 SREP\9c 165.001

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