ML20038B139
| ML20038B139 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 11/13/1981 |
| 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, NUDOCS 8111240763 | |
| Download: ML20038B139 (3) | |
Text
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November 13, 1981 373-4o83 I
Mr. James P. O'Reilly, Director U. S. Nuclear Regulatory Commission-Region II 101 Marietta Street, Suite 3100 j
Atlanta, Georgia 30303 Re: Catawba Nuclear Station Units 1 & 2 Docket Nos. 50-413 and -414 4
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Dear Mr. O'Reilly:
l Pursuant to 10 CFR 50.55e, please find attached Significant Defici
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Report SD-413, 414/81-25.
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Office of Inspection and Enforcement Attorney-at-Law I
U. S Nuclear Regulatory Commission 314 Pall Mall I
Washington, D. C. 20555 Columbia, South Carolina 29201 l
f; NRC Resident Inspector Palmetto Alliance Catawba Nuclear Station 2135 Devine Street Columbia, South Carolina 29205 i
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DUKE POWER COMPANY Catawba Units 1 and 2 Report: SD 413, 414/81-25 Report Date:
11/13/81 Facility: Catawba Nuclear Station, Units 1 and 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.
Description of the Deficiency: Westinghouse notified Duke Power Company that they had discovered a generie problem with their sal differential relays in that they would not pass the full surge withstand requirenant of the ANSI Standard 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, for example, the relay could possibly give a false trip output.
At Catawba, the sal relay is used to protect the Class lE diesel generators (emergency AC on-site power sources) against short circuits. Each diesel generator is protected by its own respective relay.
If a given sal calls for a trip, the affected diesel generator's main circuit breaker will trip.
A shutdown of the diesel engine and generator will also occur.
Initial Report: 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, N. C. 28242.
Analysis of Safety Implication:
If a situation were to occur at a Catawba unit in which all offsite power was lost, the two Class 1E 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 1E AC power sources would be lost until it could be determined that a false trip had occurred.
In order to restore power to the affected train, the lockout relay tripped by the SA1 relay would first have to be reset.
The affected diesel generator would then have to be restarted and loaded.
In the situation described above, there would be no affect on the health and safety of the public. The AC power required to shut down the plant would be provided by the unaffected diesel generator.
Note--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.
Duke Power Company has employed the Westinghouse sal relay in various applica-tions 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
1 Report No. SD 413, 414/81-25 Page 2 i
scenario occurring is judged extremely remote.
Corrective Action: Westinghouse has available modification kits for the SA1 relays that can be used to upgrade the surge withstand ability to that called for in ANSI C37.90-1978. These kits are being ordered and are expected to be installed by January 1, 1983.
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