ST-HL-AE-3955, Special Rept:On 911206 & 07,standby DGs 23 & 21 Tripped W/ No Test Mode Trips Indicated When Released from Emergency Mode.Cause Not Known.Work Packages Developed to Troubleshoot Standby DGs & to Determine Causes of Trips

Special Rept:On 911206 & 07,standby DGs 23 & 21 Tripped W/ No Test Mode Trips Indicated When Released from Emergency Mode.Cause Not Known.Work Packages Developed to Troubleshoot Standby DGs & to Determine Causes of Trips

ML20091J133
Person / Time
Site:	South Texas
Issue date:	01/03/1992
From:	Jump W HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-3955, NUDOCS 9201070359
Download: ML20091J133 (4)

Text

01/29/92 15:14 3129728299 002

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stI N /955 Tile No.: G02 10CFR50 U. S. Nuclear R*5ulatory Consission Attention: Documetit Oontrol Desk Washington. DC 20555 Suuth Texas Project Electric Generatin5 Station Unit 2 Docket No. STN 50-499 Special Report Regarding Two Digigl_ Generator Non Va]'d Failuran

- Pursuant to the South Texas Proje.ct Electric Generatin5 Station (STFEGS)

Technical Specifications 4.8.1.1.3 and 6.9.2, Houston Lighting & Power submits the attached Special Report regarding Standby Diesel Generat. ors (SDG) #23 and

1. 21 non-valid failures which occurred on December 6 and 7, 1991, respectively.

If you shou?,d have any questions on this matter, please contact Mr. C. A. Ayala at (512) 972 8628 or myself at (512) 972 729M.

h& 0~n William J. Jump (/ 7 T Manager, Nuclear Licensing MAS /1f

Attachment:

Special Report Regardin5 Two SDC Non Valid failures n

9201070359 920103 PDR ADOCK 05000499 S PDR

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Attachment ST ItL AE 3955 Page 1 of 2 South Texas Project Electric Cunerating Station Unit 2 Docket No. STN 50 499 Special Report Regardin5 Two Diepel Generator Non-Valid railuren DLiCRIPTION OF EV E :

On December 6, 1991 at 2301 hourw. Standby Diesel Generator #13 was started in the ecer5ency mode following release of Equipment Cicarance Order 2-91-3261 which was associated with a work document. Unit 2 was in Mode 4 Juring a refuelin5 outa5e. SDC *23 came up to rated speed. roltage, sud frequency within 10 seconds. When the eu51ue was released from emer5enCY mode, SDG #23 tripped w!Lh no test mode trips indicated. The engine was then restarted at 0030 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> on December 7 in the test mode with 16C Electrical, and Mechanical Maintenance personnel present. The engine came up to rated speed, voltage, and frequency within the 10 second linit and was running satifactorily. The engine was then started a third time at 0039 hours4.513889e-4 days <br />0.0108 hours <br />6.448413e-5 weeks <br />1.48395e-5 months <br /> in the emergency mode. The diesel 5enerator vsa rolessed from the emergency mode to the test mode without a trip. The Control Room then commenced the Standby Diesel Generator *23 Operability Test. The dieaal performed satisfactorily during the one hour survat11anc6 run and SDG w23 was declared operable at 0250 hours0.00289 days <br />0.0694 hours <br />4.133598e-4 weeks <br />9.5125e-5 months <br />.

Standby Diesel Generator #21 was started on December 7, 1991 at 0313 hours0.00362 days <br />0.0869 hours <br />5.175265e-4 weeks <br />1.190965e-4 months <br /> in the emergency mode to verify operabilicy in accordanca with Technical Specification Action Statement 3.8.1.1 and came up to rated speed, volta 58 and frequency within 10 seconds. When the angine was released from tt.a emergency mode, SDC #21 tripped with no test mode trips indicated. SDC #21 was restarted in the emergency modo a second etme at 0323 hours0.00374 days <br />0.0897 hours <br />5.340608e-4 weeks <br />1.229015e-4 months <br />, released from the emetgency modo to the test mode, and the engine functioned properly. At 0603 hours0.00698 days <br />0.168 hours <br />9.970238e-4 weeks <br />2.294415e-4 months <br />, the Control Room commenced SDC #21 operability test and declared SDG #21 operable at 0820 hours0.00949 days <br />0.228 hours <br />0.00136 weeks <br />3.1201e-4 months <br />.

CAUSE OF EVENT:

The causes of these events are not known. Work documents for SD0 #23 and_n21 have been generated to troubleshout these events durin5 the next scheduled train outa5es since the diesel generators were demonstrated operable (via subsequent restarts) immediately after the trips. A previous siallar failure indicated problems with loose connections. The control panois have been inspected and no loose connections were discovered. Until these service requests have been implemented and troubleshootin5 Performed, the cause of these events cannot bo determined.

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Attachment '

ST.HL-AE 3955 Fage 2-of 2 ANALYSIS OF EVENT:-

These two events have been classified as non valid failures since the '

- ' diesel generstora operated catisfactorily in the emergency mode and if challenged, would. have performed their' safety function. SDGa #21-and #23 were started in test mode on December 15, 1991 and both engines operated ~

satisfactorily. Dissel . Benerator #21.also successfully completed a valid test cn December 19, 1991. SDGs #21 and #23 started'and ran in the emergency mode when responding to a recent reactor trip and Safety injection signal en December 24, 1991. SDG #21 tripped when released from the_ essergency modo during.the run on December 24. Subsequently, a separate report.for this apparent non-valid failure will be submitted addressing-_the cause of the EDC trip. Since these SDGs have operated correctly in the emergency mode, the diesel generators are considered capable-of fulfilling their required safety functions.

CORRECTIVE ACTIONS:

1. Worn packages have been' developed to troubleshoot the SDGs and

- determine the causes of the trips. The troubleshootirq of SDC

1. 21 and #23 during their train-outales is scheduled for March 10, 1992 and February 24, 1992, respectively. A supplementary report will be submitted by April 30, 1992, identifying the causes-and necessary corrective actions.

ADDITIONAL IMORMATTON:

In accordance with Technical Specification Table 4.8-1, there have been no valid failures in the last 20 valid tests and less than 4 valid failures in.

the last 100 tests for SDG m21. n e testing frequency will remain at once per.

L31 days.

In'accordance with Technical Specification Table 4.8-1. there have been-no valid failuros-in the last-20 valid tests and less than 4 valid failures in the last 100 tests fer SDG #23. The testing frequency will-also remain at-

- once per.31 days.

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