ML20091P800
| ML20091P800 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 01/06/1992 |
| From: | Tuckman M DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9202040031 | |
| Download: ML20091P800 (2) | |
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h t-3 C. Tf; poja,y/.yt?6 f a t CD tG ountriowcn Jarwary 6,1992 U. S. Nuclear Regulatory Commission ATrN: Document Contrcl Desk Washington, DC 20.i55 Subjecti Catawba Nuclear Statioc. Unit 2 Docket No. 50-414 Soecial Report Valid Failute of Diesel Generater 2A Purtuant () Technical Specification 4.8.1.1.3 and 6.9.2, find attached a Special Report concern.ng trie Unit 2 Dierel Generator A (D/G 2A) valid failure ti.at occurred on December 5,1991.
Very truly y.)urs, 8
- h. 'Ll \\;.*hr M. S. Tuckn.an CRL/DG2/.16.92 Attachttent xt:
E. D. Ebneter Regional Adminintator, Region if W.= T. Orders Serior Ruident inspector R. E. Martin, ONR't 9202040031 920106 gDR ADOCK 05000414 PDR 1.'64
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SPECIAL REPORT 1
CATAWilA NUCl. EAR STATION DIESEL. GENERATOR 2A VAI.lD Fall.Ullii nUE TO SilOUENCER TIMER FAILURE A valid failure of Diesel Generator (D/G) 2A occurred on December $.1991 due to a failure of a timer in the lead sequencing circuitry. This failure occurred during Unit 2 Refueling Outage End of Cycle 4 (EOC) A Train Engineered Safety Features (ESP) testing.
i-D/G 2A was on a weekly testing frequency at the time of tF failure. Unit 2 was in Mode 5 at the time. This is the 2nd valid failure in the last 20 valid tests and 5th valid failure in the last 100 valid tests. There is no unavailability time associated with this failure since Technical Specifications require only one operable D/G during Mode 5. Since D/G 2D was operable, the 2A D/G was not required. D!G 2A remains on a weekly test frequency in accordance with Technical Specification 4.8.1.1.2 Table 4.8-1.
At approximately 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br /> on Deember 5.
1991. Perforreance began the Blackout /LOCA portion of the ESF testing per PT/2/A/4200/09. A 2 out of 3 degraded bus signal was initiated followed by a Safe:y injection signr1 which caused the incoming feeder breaker to the ETA btn to trip anj D/G ?A to start as designed. All loads were shed as required and the D/G ca.mc up to s] eed. At this point, the D/G breaker closed and was ready to accept loads. Howe.er, none of the load groups were sequenced onto the ETA bus. The test was halted and the D/G was manually shutdown to protect the engine since Nuclear Service Water (RN) con'ing water was unavailable when this load was not sequenced on. Performance initiated Work Request 91097849-01 for the Instrumentation
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and Electrical section (IAE) to :nvestigate and repair the cause of the sequencer failure.
. IAE checked the operation of several timers /relrys and it was discovered that time delay modul ^1C(TRAt T)in cabinet 2DOLSA-1 was broken. This timer provides a momentary reset signal to the sequencer when a blackout and a LOCA exist simultaneously for 0.5 seconds. The Normally Open output contacts for this module were stuck in the closed position even when there was no power applied to the timer. This caused relay 11B(TRA2) in 2DOLSA 1 to be continuously energized, Normally closed contact 5 and 5a on lill relay are suppose to momentarily open to drop out all committed sequencer-time delay loading relays on a reset. Ilowever, with the failed timer, this contact never returned to the closed position to allow the loading process to begin. IAE replaced the timer and Performance completed their ESF testing with no other problems.
The failed part is a Cutler-Ilammer Model #D87XDL30 off delay timer. No similar type failures of this model of timer have been seen at Catawba. The timer had been tested on 10/29/91 per predefined work ordcr # 91035580-01 and found to be out of calibration but not failed in a manner where the output contacts would not change states. All sequencer time delay relays for each D/G are tested each outage to verify their correct calibration and operation.
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