ML20004C521

Significant Deficiency Rept SD 413/81-04 Re Weld Leaks on gas-filled Loadcenter Transformers 1ETXC & 1ETXE,initially Reported on 810501.All Weld Leaks Have Been Repaired & Transformers Refilled W/Freon

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)

Text

-.

. n, _

T

/

DUKE POWER COMPANY k

?

Powca Dutto:No 422 SouTu CnuHcu Srazer, CnAHwTTE. N. C. 282.&2 wi w a m o. e* L en.an.

v.e, p.c.. .,e May 29, 1981 ct c. . c: . 7e.

$rcase P.00wCtioes 373+aC83 Mr. James P. O'Reilly, Director '

& @// '

U. S. Nuclear Regulatory, Commission Region II [S \\0 f(h Q M j; f(.

gg32N7 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 ' --j m Re: Catawba Nuclear Station @

9, h* //

Unit 1 /f p Docket Nos. 50-413 and 50-414 \^5 / /i-

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

i l

h 22f.

8106040 Sil[

m, w g ,. ,

g. m  ; .

[ ; ',

,( @ _f-p o.3

+-

. CATAWBA NUCLEAR STATION-REPORT NUMBER: .SD 413/81-0.4~

~ ~

-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.

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 -l

' 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. l H

e

.l

.n .. fs 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.

l t

m_ -4