05000254/LER-1981-002-03, /03L-0:on 810107,Unit 1 Emergency Diesel Generator Tripped & Failed to Restart.Caused by Loose Fuse in 125 Vdc Engine Starting & Fuel Control Circuit & Misalignment of Output Breaker Auxiliary Contacts.Fuse Holder Tightened
| ML20003A312 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 01/20/1981 |
| From: | Mendenhall E COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20003A309 | List: |
| References | |
| LER-81-002-03L, LER-81-2-3L, NUDOCS 8102030475 | |
| Download: ML20003A312 (3) | |
| Event date: | |
|---|---|
| Report date: | |
| 2541981002R03 - NRC Website | |
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60 61 COCK ET NU'.'9 E R ba 63 EVENT CATE 14 75 RE* ORT DATE 40 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h t o !:l l While demonstrating Unit 1 Emergency Diesel Generator operability af ter monthly l
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res ta rt the Diesel Generator failed when proper speed co strol could not be
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33 JS 36 31 40 41 42 43 44 41 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h ltloll Investigation showed a loose fuse in the 125 VDC engine starting and fuel control l
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gl contacts was also found. The fuse holder was tightened and the breaker auxiliary l
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service at 1705 on January 7,1981.
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LER NUMBER:
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LICENSEE NAfiE: Commonwealth Edison Company Quad-Cities Nuclear Power Station Ill.
FACILITY NAME: Unit One IV.
DOCKET NUMBER: 050-254 V.
EVENT DESCRIPTION
On January 7,1981, at 0855, the Unit One Diesel Generator and its circuit breaker to the emergency 4-KV Bus 14-1 tripped. The Diesel Generator had been running for ten minutes while performing surveillance QOS 6600-1 following the routine monthly preventative maintenance inspection (QMP 200-1). Attempts to restart the Diesel failed when proper speed control of the Diesel could not be achieved. The Diesel Generator was taken out of serv:ce at 0930.
VI.
PROBABLE CONSEQUENCES OF THE OCCURRENCE:
Work Request Number Q310309 was issued to repair the Unit One Diesel Generator. Technical Specification 3.9.E.1. was immediately satisfied by demonstrating the operability of LPCI, Core Spray, and all loops of the containment cooling mode of the RHR System; and the availability of two 345 KV of f-site sources of auxiliary power. Continued reactor operation is permissible for 7 succeeding days, provided the above systems are demonstrated operable immediately and daily thereaf ter, or the Diesel Generator is returned to service and demonstrated operable.
In addition, the Unit 1/2 Diesel Generator was demonstrated operable immediately prior to initially taking the Unit One Diesel Generator out of service for the maintenance inspection. The continued availability of three redundant sources of power to the Emergency Bus and the complete operability of all ECCS and containment cooling systems minimized the impact of the equipment failure on overall reactor safety.
Vll. CAUSE:
Upon investigation, a loose fuse was found in the holder of the 125 VDC engine starting and fuel control circuit. The poor contact in the circuit caused a low, erratic voltage on the synchronizing motor in the Woodward Governor on the Diesel.
The resulting loss of speed control caused the Diesel and its circuit breaker to trip. After tightening the loose fuse holder an attempt was made to verify the Diesel Generator's cperability from the Control Room at 1105 on January 7 At this time the Diesel ran properly and the Generator was synchronized to the Bus, but the Diesel Generator output circuit breaker would not close.
Failure of the breaker to properly close was found to be a slight misalignment of the auxiliary contacts.
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CORRECTIVE ACTION
i The clips on the fuse holder were tightened to make a good contact.
This action corrected the erratic engine speed control that caused the system failure. The breaker auxillary contacts were also adjusted i
and tested for proper alignment.
Unit One Diesal Generator was returned to service at 1705 on January 7, 1981, and ran successfully for two hours.
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