ML20084R317
| ML20084R317 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 07/09/1973 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084R320 | List: |
| References | |
| BBS-73-142, NUDOCS 8306150063 | |
| Download: ML20084R317 (8) | |
Text
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c3 Mr. John F. O' Leary, Director Directorate of Licensing U. S. Atomic Energy Commission Washington, D. C.
20545
Dear Mr. O' Leary:
SUBJECT:
Quad-Cities Nuclear Power Station Units 1 and 2, Docket #50-254 and 50-265, DPR-29 and 30, Appendix A, Sections 1.0.A.4 and 6.6.B.1 The purpose of this letter is to inform you of the details concern-ing an abnormal occurrance which took place on July 1, 1973 whereby the shared diesel generator was inoperable due to a loss of control power.
This occurrance was reported to you by telegram on July 2.
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PROBLEM AND INVESTIGATION About 3:30 p.m. on July 1, 1973, Unit 1 was at a steady power level of 780 MWe and Unit 2 was operating at 460 MNe.
At that time, the control room operators were changing shifts.
The Unit 1 operator observed that the green STOP light at the control switch for Standby Diesel-Generator 1/2 on panel 901-8 was not illuminated.
A burned out light bulb was immediately suspected, but after replacing the bulb, the situation was not corrected.
Attempts were made to start the diesel from both the control room and from the local engine panel without success.
Both Unit 1 and 2 diesel generators were operable at that time.
An immediate investigation at the local engine control station for Diesel Generator 1/2 revealed that fuse F24 in the engine starting and fuel control circuitry was blown.
This resulted in an open circuit and prevented the diesel from starting either manually or automatically.
The blown fuse was replaced; however, the immediate cause of the overload was not known.
At 5:00 p.m. on July 1, the 1/2 diesel was declared operable.
The diesel generator was started, loaded, and run for one hour.
No de-ficiencies or abnormalities were observed during this time.
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EVALUATIONS AND CORRECTIVE ACTIONS A.
SAFETY IMPLICATIONS The exact duration of time which Diesel Generator 1/2 was not operable is unknown.
However, the diesel operated satisfactory on June.29 for one hour.
Monthly maintenance checks were per-formed later that day on the fuel, coolant, lubrication, and starting air systems.
Unit 1 diesel was also run on June 29 and Unit 2 diesel was operated on June 30.
During the. time when the diesel was inoperable, both Unit 1 and 2 diesels were completely operable.
All 345 KV lines and re-serve auxiliary power transformers T12 and T22 were always avail-able.
The overall safe operation of the plant was thus not affected during the time which the 1/2 diesel was inoperable.
B.
DETERMINATION OF CAUSE At 8:00 a.m. on July 2, electrical maintenance personnel began an investigation of the exact cause of the blown fuse at the engine control cabinet.
The indicating bulb which was removed from panel 901-8 on July 1 was found to have the filament in-tact, but the contact point at the tip was. charred and burned out.
The bulb socket assembly was removed and the entire inside threaded area was charred.
The contact at the base of the socket was no-ticeably burned and' blackened.
Pieces of this contact were lying at the bottom of the socket.
It.is postulated that a loose bulb or loose contacts in the socket caused an arcing effect in the socket.. This resulted in a carbon buildup, short circuit, and a subsequent blown fuse.
The defective socket assembly was replaced.
There have been no previous occurrances of a simular nature which have caused blown fuses or essential equipment to become inoperable.
C.
CORRECTIVE ACTIONS The indicating lamp sockets and bulbs bar the Unit 1 and 2 diesel generators have been checked satisfactcry.
Control Rcom Opera-tors have been cautioned as to the proper replacement of indica--
ting bulbs on all lights in the control room.
A modification is being, considered.which would provide a control room _ annunciator for a power failure.in the control circuitry.
This will indicate a blown fuse or short. circuit.in the' engine start and fuel control wiring for each diesel generator,. and-
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will give immediate indication of diesel inoperability in these cases.
D.
EVALUATION OF CUMUIATIVE EXPERIENCE FOR SAFETY IMPLICATIONS Based on cumulative experiences, similar failures have not occurred on any diesel generator or on other systems in the plant.
Therefore, continued safe operation is not affected by this incident.
Respectful y,.
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B. B. Ste /
enson Station Superintendent l
BBS:LG/dp BBS-73-142 I
cc:
Regional Director Directorate of Regulatory Operations - Region III l
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