ML19317G040
| ML19317G040 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 01/02/1975 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19317G041 | List: |
| References | |
| 408, NUDOCS 8002210742 | |
| Download: ML19317G040 (2) | |
Text
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SACRAMENTO MUNICIPAt UTILITY DISTRICT C 1708 59th Street, Box 15830, Sacramento, Cahfornia 95813;(916)452-3211 January 2, 1975 2
Director Directorate of Licensing
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U.S. Atomic Energy Commission g
Washington, D.C.
20545
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'l Re: Operating License DPR-54
.' '. : s" ~.f' g Docket No. 50-312 Abnormal Occurrence A0-50-312-74-l'l 43
Dear Sir:
As defined by Technical Specifications for the Rancho Seco Nuclear Power Station, Section 6.12.2B, we are reporting the following abnormal occurrence as A0-74-13.
.During a special test prior to performing preventive maintenance L
on Diesel Generator "B",
the Diesel Generator "A" would not start. At
/
, 0922 on December 3, 1974, the "A" Diesel Generator start was attempted from
(
)theCentrclRoc=. TSc Diccel Recs fanc and engine fuel oil pump cterted,
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the engine run light'on the local ' control panel came on, went off and stayed off. The starting air motors did not run and therefore the diesel did not start. The manual air valves were checked open and starting air pressure r
was at 250 psig.
The "A" Diesel "Stop" BLPB in the Control Room was pushed, the engine auxiliaries went through their <,hutdown sequence as if the engine had been running.
An inspection of the diesel generator control circuit revealed that the Dynalco Relay Tachometer had malfunctioned in such a manner that it blocked the energizing of the diesel nir start solenoids which prevented the diesel from starting. The defective relay tachometer was removed and a new one was calibrated, installed and tested.
An inspection of the original relay tachometer indicated that three zener diodes in the speed switch had overheated and failed. This in turn caused the relay tachometer to malfunction. To determine what caused the l
zeners to overheat and how to prevent this problem from reoccurring, the damaged relay tachometer was returned to Dynalco Corporation for more testing.
Based on this testing, Dynalco will supply the District with the necessary nformation to prevent this type of failure. Until a final solution is determined, the Plant Review Committee recommended'the following program be followed on both the A & B Diesels.
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-3 Director Directorate of-Licensing January 2, 1975 1)
~0n a daily basis electrically test diode voltage. This voltage should be 22.5 volts + 2.5 volts. The information should be recorded for. future use. This data will verify that the zener diodes have not failed.
If the measured voltage is not within the limits set above, the switch should be removed and a new one installed.
2)
Connect a spare relay tachometer to DC bus "A".
On a daily basis measure the voltage across the three zeners_and on a weekly basis visually. inspect the zener diodes for heat damage. This setup will. allow extensive long term testing of a speed switch without making the diesel-generator inoperative.
2 The Plant Review Committee determined that if the above testing is performed there will be a sufficiently high reliability for starting either diesel generator.
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'There was no plant transient associated with this occurrence.
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The diesel-generator is a Bruce, G.M. Diesel, Type G8G65 rated at
/'2750.KW.
3 The techometer is manufactured by Dynalco Corporation, Type RT 2450 with a frequency-range of 0 to 5300 Hertz.
This is the third Abnormal Occurrence Report concerning this tachometer. The previous failures were
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reported as A0-50-312-74-1 and A0-50-312-74-8.
I A detailed analysis is being undertaken by Generation Engineering Department to resolve the failure and to design a system to prevent re-i
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occurrences.
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Respectfully, l'
J. J. Mattimoe l
Assistant General Manager and Chief Engineer
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~ Enclosure
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cc:
R._H. Engelken, Region V
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