ST-HL-AE-3928, Special Rept:On 911025,fuel Oil Leak Found at Injection Pump 9L of Standby Diesel Generator 21.Caused by Crack on Threaded Portion of Delivery Valve Holder.Holder Will Be Replaced W/New Cooper-Bessemer Holder by Next Outage

Special Rept:On 911025,fuel Oil Leak Found at Injection Pump 9L of Standby Diesel Generator 21.Caused by Crack on Threaded Portion of Delivery Valve Holder.Holder Will Be Replaced W/New Cooper-Bessemer Holder by Next Outage

ML20086F661
Person / Time
Site:	South Texas
Issue date:	11/25/1991
From:	Jump W HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-3928, NUDOCS 9112030361
Download: ML20086F661 (4)

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llou$ ton I.ighting A Pm o November 25, 1991 ST llL AE 3928 File No.: CO2 10CFR50 U. S. Nuclear Regulatory Cotanission Attention: Document Control Desk Vashington, DC 20555 South Texas Project Electric Generating Station Unit 2 Docket No. STN 50 499 Special Report Regarding Standby Diesel Generator 21 Nonvalid Failure on October 25. 1991 Pursuant to the South Texas Project Electric Generating Station Technical Specifications 4.8.1.1.3 and 6.9.2, llouston Lighting & Power Company submits the attached Special Report regarding the Standby Diesel Generator nonvalid fallure that occurred on October 25, 1991.

If you should have any questions on this matter, please contact Mr. C. A. Ayala at (512) 972 8628 or me at ($12) 972-7205.

.Y 60 William J . Jump Manager, Nuclear Licensing RAD / amp

Attachment:

Special Report Regarding Standby Diosel Genet atc.r 21 Nonvalid Foilure on October 25, 1991

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. ST liL AE- 3928 File No.: G02 llouston Lighting & Power Compar.y

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Regional Administrator, Region IV Rufus S. Scott Nuc1 car Regulatory Cornmission t.ssociate General Counsel 611 Ryan Plaza Drive, Suite 400 llouston Lighting & Power Company Ar}ington, TX 76011 P. O. Box 61867 llouston, TX 77208 George Dick, Project Manager U.S. Nucient Regulatory Conaission INTO Washington, DC 20555 Itecords Center 1100 circle 75 Parkway J. 1. Tapia Atlanta, CA 30339-3064 Senior Resident inspector --

c/o U. S. Nuclear Regulatory Dr. Joseph M. llendrie Cot nission 50 Se11 port Lane P. O. Box 910 Be11 port, NY 11713

$ Bay City, TX 77414 D. K. Lacker J. R. Newman, Esquire Bureau of Radiation Control Newman 6 iloltzinger, P.C. Texas Department of llealth 1615 L Street, N.W. 1100 West 49th Street Vashington, DC 20036 Austin, TX 78756 3189 D. E. Ward /T. M. Puckett Central Power and Light Cortpany P 0. Box 2121 Corpus Christi, TX 78403 J. C. Lanier/M. B. Lee City of Austin Electric Utility Department P.O. Box 1088 Austin, TX 78767 K. J. Fiedler/M. T. liardt City Public Service Board P. O. Box 1771 San Antonio, TX 78296 Revised 10/11/91 L4/NRC/

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Attachment ST !!L.AE.3928 Page 1 of 2 South Texas Project Electric Generating Station Unit 2 Docket No. STN 50 499 Special Report Regarding Standby Diesel Generator 21 Nonvalid Failure on October 25. 121 DESCRIPTION OF EVENT On October 25, 1991, Unit 2 was in Mode 6 during a refueling cutage. At approximately 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />, during the performance of Standby Diesel Cenorator

- (SDG) 21 twenty four (24) hour load test, SDG 21 was found to have a fuel oil leak at injection pump 9L. The SDG was unloaded and the test was terminated at 1410 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.36505e-4 months <br /> oue to the size of the leak (0.3 gpm). The location of the Icak was not considered to be a fire hazard, A crack was found on the threaded portion of the delivery valve holder during troubleshooting of the injection pump. On October 25, 1991, the delivery valve holder was replaced.

On October-- 25,1991, at 2154 hours0.0249 days <br />0.598 hours <br />0.00356 weeks <br />8.19597e-4 months <br />, a second 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> load test commenced and was completed satisfactorily on October 27, 1991 at 0136 hours0.00157 days <br />0.0378 hours <br />2.248677e-4 weeks <br />5.1748e-5 months <br />.

There have been similar events at STPEGS in which cracks were found across the threads of the delivery valve holders. -These failures were initially attributed'to overstressing the fittings due to improper torquing practices during field assembly. The installation procedure was revised in October,

' The incidence of new 1990 to: clarify installation and torquing requirements.

cracks has not been eliminated by utilizing this installation method. The failures have now been attributed to concerns with the design of the delivery valve holder, as noted below. STpEGS is evaluating this condition to determine if 10CFR21~ applies.

There is also a history of delivery valve holder failures at other utilities.

MPR Associates (the Cooper Bessemer Owners Group (CBOG) Project Engineer) has f tested a new 60 degree svaged tapered design being used on Trans America . _

! Delaval Inc. Enterprise diesel generators. The tapered design was tested by-tightening it from 36.f t-lb to 250 f t.lb with no evidence of cracking or leaking. -In addition, STPEGS is currently _ pursuing a design change which ,

involves machining-the existing delivery valve holder to relocate the ferrule-seat within a stronger portion of the delivery valve holder. This will provide a configuration that is more resistant to cracking.

CAUSE OF_THE EVENT 1

l. : The cause of the event is the delivery valve holder design which is prone to L - cracking.

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SRf.M 91 317.01A i

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Attachment ST HL AE-3928 Page 2 of 2

{ .m South Texas Project Electric Generatine, Station 1 jhk, Unit 2 ltw Docket No. STN 50-499 Cf stal Report Regarding Standby Diesc1

g[c ' y fenerat p alid Failure on October 25. 1991 h ' J Q .- D.\.RF EVENT:

o 1 eted at I operated suti-factorily in the emergency mode; however, due s the .e of the leak fera the injection pump the diesel was secured.

.. .- tau ring su emergency, SDC 21 would have started and loaded as required and with

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r,perator intervention the affected fuel pump could oe isolated. Even though t

( inis failure of tha delivery valve holder iu attributed to a design problem,

p. continued plant operation is justified. The probability of additional

de 'very valve holder failures on taultiple cylinders in multiple SDG's (Each STPEGS SDG

- coli . dent with a loss of offsite power event is very small.

can carry demian basis load with 2 of the 20 cylinders inoperable.) In the event that a delivery valve hol ir failure occucs, provisions are in place to assure that the affected SDG fuel injector is isolated including:

a) increased monitoring while the engine is in operation, bf b) written instructions to isolate cylinders associated with leaking delivery valve holders.

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CORRECTIVE ACTIONS.1 The following corrective actions are being taken:

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1. The injection pump 9L delivery valve holder was replaced on October 25, 1991.

2. A design change tu ;1 ace the delivery valve holder with the new Cooper-Bessemer Owners Croup recommended design or an equally acceptable modification of the existing delivery valve holders will be installed at the first opportunity, but, no later than the next refueling outage in each unit. The Unit 1 and Unit 2 refueling outages are scheduled for the Fall 1992 and Spring 1993 respectively.

ADDITIONAL INFORMATION:

Por STPEGS Technical Specification 3.8.1.1, there have been no valid failures in the last 20 valid tests of SDC 21 and the number of valid failures in the last 100 valid tests is less than four, therefore, the testing frequency for SDG 21 remaic.- t once per 31 days.

1 SEP W1-317.01A c

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