ML20033C087
| ML20033C087 | |
| Person / Time | |
|---|---|
| Site: | Mcguire |
| Issue date: | 11/16/1981 |
| From: | Parker W DUKE POWER CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, SD-370-81-10, NUDOCS 8112020646 | |
| Download: ML20033C087 (2) | |
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DUKE POWER COMPANY POWER BUILDING 4cc Socru Cnuncu STREET, CnAHLOTTE, N. C 2s24a h
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WILLIAM O. PA R M ER, J R.
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TELEPMont:Anta 704 November 16, 1981 273-4o83 s1t.- P.ooverio, m
Mr. James P. O'Reilly, Director U. S. Nuclear Regulatory Commission Region II
[h 101 Marietta Street, Suite 3100 1.11,,)
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Atlanta, Georgia 30303 m
DECI 1981 s l
1 Re: McGuire Nuclear Station E"gmau 7
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Unit 2 Docket No. 50-370 to
Dear Mr. O'Reilly:
Pursuant to 10CFR 50.55e, please find attached Significant Deficiency Report SD 370/81-10 concerning Westinghouse's discovery that their sal relay will not pass the requirements of ANSI C37.90-1978. This has been previously reported for Unit 1 as LER 369/81-162.
This report is being submitted 1 working day late. We apologize for any incon-venience this may have caused.
/
Very truly yours pWilliamO. Parker,Jr.
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s PEN /smh Attachment cc: Director Ms. M. J. Graham Office of Inspection & Enforcement NRC Resident Inspector U. S. Nuclear Regulatory Commission McGuire Nuclear Station Washington, D. C.
20S55 Wp;t Af. T j
8112O20646 811116
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PDR ADOCK 05000370 S
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McGUIRE NUCLEAR STATION SIGNIFICANT DEFICIENCY REPORT:
SD-370/81-10 REPORT DATE: 11/16/81 FACILITY: McGuire Nuclear Station, Unit 2 IDENTIFICATION OF DEFICIENCY: Westinghouse has discovered that their sal relay will not pass the requirements of ANSI C37.90-1978. This deficiency was brought to our attention through letters dated 7/23/81 and 10/1/81. On October 16, 1981, Mr. A. Ignatonis of the NRC Region II office was contacted and notified of this item by W. O. Henry and W. J. Foley of Duke Power Company, Charlotte, NC 28242.
DESCRIPTION OF THE DEFICIENCY: Westinghouse notified Duke Power Company that they had discovered a generic problem with their sal differential relays in that they would not pass the full surge withstand requirements of the ANS1 Star.dard C37.90-1978. This standard requires that a relay withstand a 2.4KV crest value of a test oscillatory wave and their tests indicate possible failures above a 1.8KV crest.
If such a surge were to be present on the 125 VDC control power inputs to the relay, the relay could possibly give a false trip output.
At McGuire, the sal relay is used to protect the Class lE diesel generators (emer-gency AC on-site power sources) against the short circuits.
Each diesel generator is protected by its own respective relay.
If a given sal calls for a trip, the af-fected diesel generator's main circuit breaker will trip. A shutdown of the diesel engine and generator will also occur.
ANALYSIS OF SAFETY IMPLICATIONS: If a situation were to occur at McGuire Unit 2 in which all offsite power was lost, the two diesel generators (train A and train B) would provide the required onsite AC power.
In the event that a given surge above the withstand capability of the sal then caused a relay to false trip, one of the two onsite AC power sources would be Icst until it could be determined that a false trip had occurred.
In order to restore power to the affected train, the lockout re-lay tripped by the sal relay would have to first be reset. The affected diesel gen-erator would then have to be restarted and loaded.
A given surge causing a trip of an sal would affect only one relay since each diesel generator's sal relays are powered by independent DC systems and connected to their respective independent current transformers. The AC power required to shutdown the plant would be provided by the unaffected diesel generator. Thus, there would be no affect on the health and safety of the public.
Duke Power Company has employed the Westinghause sal relay in various applications for years in both Class lE and non-Class lE service. A false trip attributable to surges has never occurred. The probability of the above scenario occurring is judged extremely remote.
CORRECTIVE ACTION: Westinghouse has available modification kits for the sal relays that can be used to upgrade the surge withstand ability to that called for in ANSI C37.90-1978. These kits are being crdered and are expected to be installed by July 1, 1982.
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