ML20012F127

Supplemental Special Rept:Correcting Design Description of Jacket Water Temp Switch,Per Two Nonvalid Failures of Standby Diesel Generator on 880813 & 26.Design Affects Extent of Corrective Action Taken to Prevent Recurrence

ML20012F127
Person / Time
Site:	South Texas
Issue date:	03/29/1990
From:	Vaughn G HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-3415, NUDOCS 9004100193
Download: ML20012F127 (5)

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COBtpting Houston Lig & PoweranySouth Temas Projut Eledric P.O.Bos209 Gmroting Wadsworth. Tesas 77483 Stati i

March 29, 1990 ST-HL-AE-3415  :

File No.: 002 10CFR50.36(c)(5)

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

Washington, DC 20555 l f

South Texas Project Electric Generating Station Unit 1 Docket No. STN 50-498 Supplemental Special Report ,

Regarding Two Nonvalid Failures of #13 Standby Diesel Generator on Aur.ust 13 and 26, 1988  ;

On September 12, 1988 Houston Lighting & Power submitted a Special i

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Report regarding two'nonvalid failures of the #13 Standby Diesel Generator under letter number ST-HL-AE-2776. We have subsequently discovered an error in the description of the design of the jacket water temperature switch which affected the extent of the corrective action taken to prevent recurrence of the event. Therefore, pursuant to Technical Specification 4.8.1.1.3 and '

6.9.2, HL&P submits the attached supplemental report.

If you should have any questions on this matter, please contact Mr. C. A. Ayala at (512) 972-8628 or myself at ($12) 972-7921.

1. f f G. E. Vaughn Vice President Nuclear Operations BEM/n1

Attachment:

Supplemental Special Report  ?

Regarding Two Nonvalid Failures of #13 Standby Diesel Generator on August 13 and 26, 1988 9004100193 900329 PDR ADOCK 05000498 S PDC NL.89.346.01 A Subsidiary of flouston Industries incorporated ((M ,

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ST*HL' AE 3415 Nouston Lighting & Power Compan)-

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Pile No. : CO2 South Texas Project Electric Generating Station Page 2 i

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Regional Administrator, Region IV Rufus S. Scott I Nuclear Regulatory Commission Associate General Counsel 611 Ryan Plaza Drivo, Suite 1000 Houston Lighting & Power Company Arlington, TX 76011 P. O. Box 61867 >

Houston, TX 77208 Coorge Dick, Project Manager U.S. Nuclear Regulatory Commission INPO Washington, DC 20555 Records Center 1100 Circle 75 Parkway J. I. Tapia Atlanta, GA 30339 3064 Senior Resident Inspector c/o U. S. Nuclear Regulatory Dr. Joseph M. llendric Commission 50 Be11 port Lane P. O. Box 910 Bellport, NY 11713 Bay City, TX 77414 D. K. Lacker ,

J. R. Newman, Esquire Bureau cf Radiation Control

'Newman & lloltzinger, P.C. Texas Department of llealth 1615 L Street, N.W. 1100 West 49th Street Washington, DC 20036 Austin, TX 78704 D. E. Ward /R. P. Verret Central Power & Light Company P. O. Box 2121 Corpus Christi, TX 78403 J. C. Lanier Director of Ceneration City of Austin Electric Utility i 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

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Page 1 of 3 j

South Texas Project Electric Generating Station '

Unit 1 Docket No. STN 50-498 Supplemental Special Report  :

Regarding Two Nonvalid Failures of #13  !

Standby Diesel Generator on August 13 and 26. 1988 .

DESCRIPTION OF EVENT:

A nonvalid failure occurred on Standby Diesel Generator (SDG) #13 on August 13, and again on August 26, 1988.  !

l At approximately 0332 hours0.00384 days <br />0.0922 hours <br />5.489418e-4 weeks <br />1.26326e-4 months <br /> on August 13, 1988, with Unit 1 in Mode 3 (Hot  ;

Standby) and Standby Diesel Generator (SDG) #12 out of service for repair of a j.

leaking fuel nozzle, SDG #13 was started to meet the requirements of Technical  !

Specification Action statement 3.8.1.1.b. SDG #13 started and attained i required voltage and frequency (4160 volte and 60 Hz) within ten seconds as  ;

required. Approximately one minute later the SDG was placed in the test mode by actuating the " Release Emergency Mode Operation" pushbutton, and the SDG l tripped. Control panel indication showed that the trip was due to a jacket  ;

water high temperature shutdown signal which has a trip setpoint of 205 o ,

degrees F. Immediate investigation by the diesel operator showed the actual l Jacket' water temperature to be npproximately 130 degrees F, normal temperature l at that: point in the operatior.. Furthermore, the jacket water temperature  :

off-normal alarm, set at 190 degrees F increasing, had not actuated. Due to these observations, it was concluded that the high temperature _ trip signal was  !

most likely due to a spurious failure of an air-operated pressure switch-  ;

(Jacket Water High Temperature Shutdown Switch) to reset when the SDG was i started. The high temperature alarm cleared shortly afterward. and SDG #13 l was restarted at 0338 hours0.00391 days <br />0.0939 hours <br />5.588624e-4 weeks <br />1.28609e-4 months <br />. The high temperature alarm did not actuatel SDG# 13 operated as required and was shut down at 0342 hours0.00396 days <br />0.095 hours <br />5.654762e-4 weeks <br />1.30131e-4 months <br /> after the Technical Specification Action statement was satisfied. A Station Problem Report was generated to investigate the failure.

At approximately 1738 hours0.0201 days <br />0.483 hours <br />0.00287 weeks <br />6.61309e-4 months <br /> on August 26, 1988, SDG #13 started in response to i a Safety Injection (SI) signal associated with a reactor trip. The reactor trip and SI event are being reported separately as LIR 88-049. At 1757 hours0.0203 days <br />0.488 hours <br />0.00291 weeks <br />6.685385e-4 months <br />, when the diesel operator actuated the " Release Emergency Mode Operation"  ;

pushbutton in preparation for shutting down the diesel, the SDG tripped. As  !

in the August I? event, control panel indication showed a jacket water high temperature shutdown signal was present, with no other indication of an actual jacket water high temperature condition. With the exception of the start signal to the SDG, the two events appear to be identical.

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Page 2 of 3 i Base,4 on a nonvalid isilure of SDG $12 on August, S, 1969 it has subsequently been determined that the nonvalid f ailures described in this report may have

j. also been caused by setpoint drif t of the Jacket Water Temperature Valve which b actuate 6 the Jacket Water High Temperature Shutdown Switch. In the previous l- report of this f ailure, the Jacket Water ' temperature Valve was described as a fixed setpoint,. . fusible link type valve which required replacement each time it was,4ctuatsd. .The valve is actually an Amot model 2230C which has an adjust able setpoint and is reusable.

CAUSE OF OCC1'RRF.NCEt L

j The most protchie cause of these nonvalid failures was either failure of the

j. Jacket Water High Temperature Shutdown Switch to reset uhen SDG #13 was i started or setpoint drif t of the Jacket Water Temperature Valve.

l ANALYSIS OF EVENT:

The jacket water high temperature signal provides protection for the SDG during testing. It is bypassed when the SDG is operating in the emergency mode. In accordance with section C.2.e.(2) of Regulatory Guide 1.108, these events are classified as nonvalid fa!!ures of SDG $13 because they are attributed to spurious operation of a trip that is bypassed in the emergency operating mode.

I CORRECTIVE ACTION:

NW %e ,;4 W *

,( -' W 13 The trip ar4 renst tot 90irts, for the Jacket Water Nigh Tomparatura Shutdown .'

Switch bere ad?uat ed, and the 1D(i was tor.ted wuycessf ully.

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Further corrkotive actions regardirg Jacket Water Temperature Valve i

' :.) i .tellbrations ehd protective mr.intenance activities have been istntifief 9 thn i

% toport of twc. r.t.nn.'ad f ailurcs of SDJ W12 on August b and 7 19be 4 This i h, report was submit ted umt Y1R Ictter number ST-Hh-AE-3210 dated d4 $e ptetther % 1%. ,

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At t ac hment l 87-ML- AE- 3415 i Page 3 of 3 E ADDITIONAL INFORNATTON:

As of September 24, 1968 there had been twenty-one (21) valid testo performed L on $DG #13 since completion of the 100 hour0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> run test on Augu&t 6.1987. There l- have been no valid failures. The test interval for SDG #13 remains at 31 days.

There was one previous nonvalid failure of SDG di) on March 16. 1988, but the cause of that event was unrelated to the most recent occurrences.

L The.Jackst Water High Temperature Shutdown $ witch is a DeLaval Parkdale model r F CD-28 M1889-S! pressure switch. The Jacket Water Temferature Valve is an Amot  ;.

model 2230C.

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