ML20004C521
| ML20004C521 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 05/29/1981 |
| 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 8106040211 | |
| Download: ML20004C521 (3) | |
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DUKE POWER COMPANY k
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Powca Dutto:No 422 SouTu CnuHcu Srazer, CnAHwTTE. N. C. 282.&2 wi w a m o. e* L en.an.
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Mr. James P. O'Reilly, Director
\\\\ f(h M U. S. Nuclear Regulatory, Commission Region II
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101 Marietta Street, Suite 3100 j;
2N7 Atlanta, Georgia 30303
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9, Re: Catawba Nuclear Station Unit 1
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Docket Nos. 50-413 and 50-414
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Dear Mr. O'Reilly:
Pursuant to 10CFR 50.55e, please find attached Significant Deficiency Report SD 413/81-04.
Very truly yours, William O. Parker, Jr.
RWO/djs Attachment cc: Director NRC Resident Inspector Office of Inspection and Enforcement Catawba Nuclear Station U. S. Nuclear Regulatory Commission Washington, D. C. 20555 i
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. CATAWBA NUCLEAR STATION-REPORT NUMBER:.SD 413/81-0.4~
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-REPORT 0 ATE: -May 29, 1981 FACILITY: ' Catawba Nuclear Station,- Unit'l.
" IDENTIFICATION OF'OEFICIENCY:
- SeveralLweld leaks Were discovered on gas-filled loadcenter transformers
-lETXC and lETXE '(Westinghouse Serial Numbers WBSN0291 and WBSN0292, respectively).
L A leak,:i'f unattended, could eventually introduce air into the transformer tank.
INITIAL-REPORT:
' On May.;1,L 1981, Mr. Art Johnson of the NRC. Region II, Atlanta, Georgia was notified of this deficiency by Mr. W. O. Henry and Mr. W. J. Foley of Duke
. Power Company, Charlotte, NC.28242.
SUPPLIER AN0/0R COMPONENTS:
- Westinghouse Electric Corporation, Medium Power Transformer Division,;Sharon, Pennsylvania, manufactured these 1500KVA, 4160/600V gas _ filled transformers, which are.used'to supply ~ 600V auxiliary powe,r to e,aipment used in various
.._ C1' ass 1E functions.
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DESCRIPTION OF DEFICIENCY:
-S/N W8SN0291 (1ETXC)
A low' gas pres'sure indication (approximately 2h psig) was discovered and a
. search for leaks was conducted. Three leaks were discovered, all involving seam welds on the ra'diator.
-S/N WBSN0292-(lETXE)
~A bubble test revealed a weld leak on the' top plate of the transformer tank.
' ANALYSIS OF SAFETY IMPLICATION:
Dielectric Degradation If a transformar leak were not corrected, the normally maintained positive pressure
-could be: lost. Thermal'. cycling could eventually cause the replacement of freon i
by air, resulting in the reduction of.the high voltage BIL (Basic Impulse Insulation
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' Level) from 60.to 25 and a reduction of the low voltage BIL from 30 to 10.
It i
'should be noted that these reduced BIL levels are standard levels for dry ventilated
.i transformers of the same voltage ratings as the gas-filled transformers in question.
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Thermal Degradation If:the -transformer leak ware not corrected and the freon.in the tank were: replaced by air, the efficiency o/ heat transfer from ~the. coils to the tank wall and coolers
- would be reduced. At fall load, failure would not be eminent, but loss expected
- life-could be significant. Ine manufacturer recomments that, to avoid accelerated aging, the transformet loading, in air, should be _ restricted to' 60% of full load.
It-should be noted that maximum normal loading for'the transformers in question-is 67% ~ofafull -load rating. Loading during the station's construction phase is even less.
Loss of Gas Prevention Each ~of the transformers in question is equipped with a pressure gauge and a
-high/ low pressure relay. The. low pressure relay is set at positive 2 psig and activates a remote alarm-in the event that the pressure is' reduced to that level.
'This alarm should provido warning of a leak sufficiently in advance to allow corrective action prior to the introduction of air into the transformer. During
-the construction. phase of the station, each transformer is inspected monthly, at which time pressure and temperature readings are recorded to confirm the
-absence of leaks.
SUMMARY
If left uncorrected, the weld' leaks in question would not constitute a. threat to the ability of. the transformers to perform their: Class TE function, although -their
- qualified life'may be reduced. However, by periodic (monthly) inspections,-and by the application of a' low pressure
- (2 psig) alarm, leaks should be detected
' and corrected prior to_ the transformers reaching an accelerated loss-of-life condition.
It should also be noted that most leaks occur during an ~early stage
= of plant construction, when loading, and subsequent loss of life, is not a factor.
CORRECTIVE ACTION:
Ali~ weld leaks in question have been repaired by procedures accepted and approved by Duke Power Co - The transformers have been refilled with freon and monitoring is continued as described above.
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