ST-HL-AE-2334, Interim Deficiency Rept Re Cooling of Standby Diesel Generator High Voltage Cubicle Panel.Initially Reported on 870729.Design Mod to Increase Cooling of Panels Completed. Next Rept Will Be Submitted by 870930

Interim Deficiency Rept Re Cooling of Standby Diesel Generator High Voltage Cubicle Panel.Initially Reported on 870729.Design Mod to Increase Cooling of Panels Completed. Next Rept Will Be Submitted by 870930

ML20237K435
Person / Time
Site:	South Texas
Issue date:	08/31/1987
From:	Goldberg J HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
ST-HL-AE-2334, NUDOCS 8709040347
Download: ML20237K435 (4)

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i The Light company iiem,n,m i.,gs,img & re <, v.o.nmxivoo iime,,em.1cxe,22ooi 17is>22se2ii August 31, 1987 ST-HL-AE-2334 File No.: G12.400, G2.2 10CFR50.55(e) l U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 First Interim Report Concerning Cooling of the Standby Diesel Generator High Voltage Cubicle Panels On July 29, 1987, Houston Lighting and Power Company notified your office pursuant to 10CFR50.55(e), of an item concerning cooling of the Standby Diesel Generator high voltage cubicle panels. Enclosed is our First Interim Report on this item. We have determined this item to be reportable pursuant to 10CFR50.55(e). Our next report on this item will be provided on or before l September 30, 1987.

If you should have any questions on this matter, please contact Mr.

J. S. Phelps at (512) 972-7071. I J. H. Goldberg Group Vice Presi ent, Nuclear l RHT/hg

Attachment:

First Interim Report Concerning i Cooling of the Standby Diesel Generator High Voltage Control Panel 90 hh p L4/NRC/ic/hg-0 N

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August 31, 1987 ST-HL-AE-2334 File No.: G12.400, G2.2 Ilouston Lighting & Power Company Page 2 cc:

Regional Administrator, Region IV M.B. Lee /J.E. Malaski Nuclear Regulatory Commission City of Austin 611 Ryan Plaza Drive, Suite 1000' P.O. Box 1088 l

Arlington, TX 76011 Austin, TX 78767-8814 N. Prasad Kadambi, Project Manager A. von Rosenberg/M.T. Hardt U.S. Nuclear Regulatory Commission City Public Service Board 7920 Norfolk Avenue P.O. Box 1771 Bethesda, MD 20814 San Antonio, TX 78296 Dan R. Carpenter Advisory Committee on Reactor Safeguards Senior Resident Inspector / Operations U.S. Nuclear Regulatory Commission l

c/o U.S. Nuclear Regulatory 1717 H Street Commission Washington, DC 20555 P.O. Box 910 Bay City, TX 77414 l Claude E. Johnson Senior Resident Inspector / Construction c/o U.S. Nuclear Regulatory Commission i P.O. Box 910 Bay City, TX 77414 M.D. Schwarz, Jr., Esquire Baker & Botts One Shell Plaza Houston, TX 77002 J.R. Newman, Esquire Newman & Holtzinger, P.C.

1615 L Street, N.W.

Washington, DC 20036 i

R.L. Range /R.P. Verret Central Power & Light Company P. O. Box 2121 l Corpus Christi, TX 78403 l

l Revised 07/16/87 L4/NRC/ic/hg-0 1

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Attachment 1 ST-HL-AE-2334 Ilouston Lighting 8: Power Company File No.: G12.400, G2.2 August 31, 1987 Page 1 of 2 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 First Interim Report Concerning Cooling of the Standbv Diesel Generator High Voltage Cubicle Panels I.

SUMMARY

On July 29, 1987, Houston Lighting and Power Company (HL&P) notified the NRC of an item determined to be potentially reportable pursuant to 10CFR50.55(e). This item concerns inadequate cooling of the Unit 1 high voltage cubiele panels for the Standby Diesel Generators (SBDGs). During a 100 hour0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> test run of SBDG 13, a high temperature alarm was actuated from the associated high voltage cubicle panels. An evaluation of the event determined that the cooling for these panels required modifications to ensure internal temperatures would not exceed the equipment qualification temperature of certain safety-related equipment within the panels. If left uncorrected, shortening of the qualified life of the affected equipment could have resulted from the overheating of the i panels. Because such an event could have caused an adverse affect upon the safety of operations, HL&P determined this item to be reportable pursuant to 10CFR50.55(e).

II. DESCRIPTION OF DEFICIENCY During a 100 hour0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> test run of SBDG 13, a high temperature alacm actuated in the SBDG's high voltage cubicle panel. The alarm, which has a setpoint of 140 F, actuated at approximately twelve (12) hours into the test.  !

l In response to the high temperature alarm, the panel doors were opened to  ;

improve ventilation, and the test run was terminated. The panels contain safety related equipment that is qualified up to a temperature of 158 F (70 C). The alarm setpoint of 140 F (60 C) accounts for instrument i inaccuracies and local heating. An evaluation by HL&P Engineering and ,

the vendor (Cooper) concluded that no shortening of the qualified life of I safety related equipment occurred during this event.

III. CORRECTIVE ACTIONS HL&P has completed a design modification to increase the cooling of the Unit 1 panels. A second fan was installed in each panel opposite the I originally installed fan. In addition, drip shields over the vents in l the panels were removed to provide greater air flow capacity. A review of the design of the panels concluded that no adverse effect on their operability will result from removing the drip shields.

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Attachment 1-ST-HL-AE-2334 flouston Lighting & Power Cornpany File No.: G12.400, G2.2 August 31, 1987 Page 2 of 2 After completion of the modification, another 100 hour0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> test run of

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SBDG 13 was completed successfully.

Although the Unit 1 modification is adequate to resolve'the overheating problem, other design options are under consideration at this time for-both Units. The final solution will be discussed in the Final' Report.

1 IV. RECURRENCE CONTROL Recurrence control will be addressed in the Final Report.

V. SAFETY ANALYSIS Under test conditions, the high temperature alarm for the high voltage panel for SBDG 13 was actuated. . This alarm sounds in the control room but does not trip the associated SBDG. Under actual accident conditions concurrent with a' loss of offsite power, manual shutdown of the associated SBDG may not be practical in the event of a high temperature alarm. Therefore, the potential existed that temperatures inside the panels could exceed their qualified limit of 158 F. If the SBDG is not shut down, shortening of the qualified life of the safety related equipment within the panels could occur.

1 Although a detailed heat transfer study was not performed to determine potential peak temperatures which could occur within the panels, HL&P has assumed that, had this deficiency not been corrected, it could have had an adverse effect upon the safety of operations. Therefore, this item was determined to be reportable pursuant to 10CFR50.55(e).

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