ML20056E677
| ML20056E677 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 08/20/1993 |
| From: | Hebert J Maine Yankee |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-PT21-93 JRH-93-173, MN-93-78, NUDOCS 9308250048 | |
| Download: ML20056E677 (2) | |
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MaineYankee A f iia Bi f. E i.'E C T RiClif f!NR_197 ?
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EDISON DR!VE e AUGUSlA MAINE 04330 + (20h 62; 4
'8 August 20, 1993 MN-93-78 JRH-93-173 UNITED STATES NUCLEAR REGULATORY COMMISSION Attention: Document Control Desk Washington, DC 20555
Reference:
(a) License No. DPR-36 (Docket No. 50-309)
Subject:
10 CFR 21 InitiOl Notification for General Electric AK-25 Circuit Breakers with RMS-9 Overturrent Trip Devices Gentlemen:
On August 20, 1993, Maine Yankee concluded that a problem associated with the subject circuit breakers is reportable to the NRC in accordance with 10 CFR 21. This letter is being submitted as initial notification to the NRC as required by 10 CFR 21.21(c)(3)(i).
RMS-9 overcurrent trip devices are used on GE-AK-25, 480V circuit breakers to electrically isolate both safety related and non-safety (NNS) related loads in the event of an overcurrent condition.
The RMS-9 long-time, short-time and instantaneous trip functions are chosen to coordinate with the upstream and downstream protective devices.
This coordination ensures that an overcurrent condition or fault on a load would not result in de-energizing parallel circuits or any upstream load.
i On July 31, 1993, while in a refueling shutder Maine Yankee experienced three spumous trips of General Electric AK-25 480 voit circuit breakers on parallel circuits equipped with RMS-9 overcurrent trip devices. The spurious trips occurred simultaneously with a ground on another piece of equipment on a parallel circuit. An investigation indicated that the subject breakers may trip when subjected to a current spike that is of significantly shorter duration than tFat required to normally cause a trip.
In the event of a postulated Loss of Coolant Accident (LOCA),
non-environmentally qualified (EQ) components or cable could degrade ana cause intermittent grounds. The resulting current spikes could result in spurious tripping and de-energizing of equipment f.eeded to mitigate the consequences of an accident.
There are 8 AK-25 circuit breakers which control loads required to mitigate an accident.
These include 4 (2 on each of two trains) service water pumps (which provide the ultimate heat sink for engineered safeg ards), and 4 (2 on each of two trains) which feed various instrumentation, valves and other equipment necessary for engineered safeguards.
In addition one breaker feeds an electric driven fire pump and one t>reaker controls an auxiliary diesel generator which is used to meet 10CFR50 Appendix R requirements.
93'08250048 930820 11
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I MaineYankee
' UNITED STATES NUCLEAR REGULATORY COMMISSION MN-93-78 Attention: Document Control Desk Page 2 Maine Yankee is currently shutdown for refueling and plans to resolve this issue prior to returning to power operation.
Maine Yankee will provide more detailed information in a writton report within 30 days as required by 10 CFR 21.21(c)(3)(ii).
Very truly yours, W k,b
'8James R. Hebert, Manager Licensing & Engineering Support Department EBB / jag c:
Mr. Thomas T. Martin Mr. Charles S. Marschall Mr. E. H. Trottier Mr. Patrick J. Dostie NRC - Operations Center l
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