ML20137D648

Ro:On 851119,Keowee Hydro Unit 2 Inoperable Beyond Oconee Tech Spec Limit Due to Burned Out Laminated Copper Connection Between Two Coils.Caused by Cracked Brazement. Connector & Field Coils Will Be Replaced

ML20137D648
Person / Time
Site:	Oconee
Issue date:	11/22/1985
From:	Tucker H DUKE POWER CO.
To:	Harold Denton, Stolz J Office of Nuclear Reactor Regulation
References
NUDOCS 8511270118
Download: ML20137D648 (2)

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DUKE POWER GOMPANY

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November 22, 1985 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Reactor Commission Washington, D. C. 20555 -

Attention: Mr. J. F. Stolz, Chief Operating Reactors Branch No. 4

Dear Sir:

On November 19, 1985 at 1620 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.1641e-4 months <br /> Keowee hydro unit 2 was declared inoperable due to a burned out laminated copper connection between two coils. This incident was discussed with tile NRC staff during a conference call on November 20, 1985. Participants in this conference call included:

NRC DUKE Helen ITicolaras P. F. UiriT1 J. T. Beard M. A. Haghi Gordon Edison S. A. Holland F. Siurau R. D. Gillespie The following paragraphs provide a summary of the conference call.

On November 19 1985 Keowee H additional sysEem generation.ydro Unit the At 1620 2 was in tripped unit service due providing to a generator field ground relay. During the ensuing investigation, a damaged field coil pole connector was identified.

The generator field coil poles are connected in series by flexible straps consisting of laminated copper. The straps are connected to each coil winding by a brazement.

Apparently, a crack developed in one of these brazements and resulted in arcing and the subsequent field ground. No concrete reason could be determined for the development of the crack; however several theories are under evaluation. Corrective actions have bee,n taken to replace the connector and the field coils involved and inspect the remaining field coil pole connectors. No additional cracks or other problems have been noted as a result of the inspection.

The Oconee Technical Specification (T.S.) 3.7.2 allows for inoperability of one of the two Keowee hydro units for a period of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Currently, Duke has determined Keowee unit 1 is operable and is performing the necessary repairs to return the Keowee unit 2 to an operable status. However, due to unanticipated problems with the repair work the Keowee unit 2 can not be returned to service within the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed.

0511270118 851122 ' E PDR ADOCK 05000269 8 PDR

. Go Mr. Harold R. Denton, Director November 22, 1985 Page Two Under the provisions of T.S. 3.7.4 operating in this mode may continue up to 45 days without prior NRC approval only once in three years for each Keowee hydro unit. . These provisions of T.S.

3.7.4 were last utilized during an extended outage of Keowee unit 2 from September 18, 1984 to October 3, 1984 for a total of 16 days.

As a result, for a second outage of Keowee unit 2 in excess of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, NRC approval is deemed necessary as required by T.S. 3.7.4.

Pursuant to T.S. 3.7.4, and the agreement made during the referenced conference call, Duke Power Company requests the NRC approval for inoperability of Keowee unit 2 for a period not to exceed 29 days. This will ensure that the accumulated inoperability of Keowee unit 2 will not exceed the 45 days allowed by T.S. 3.7.4. The requested 29 days of inoperability is also

consistent with the NRC agreement reached during the referenced conference call in that the risk factor associated is not different whether the inoperability-is 45 consecutive days or not.

The_ parties in the referenced conference call agreed to continue in this mode of operation under the porvisions of T.S. 3.7.4. Unless informed otherwise by the NRC, Duke will assume that this constitutes NRC approval and utilize the provisions of T.S. 3.7.4.

Very truly yours,

/ 4 fMQ Hal B. Tucker ,

MAH: sib cc: Dr. J. Nelson Grace Regional Administrator U. S. Nuclear Regula, tory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Ms. Helen Nicolaras Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Mr. J. C. Bryant NRC Resident Inspector Oconee Nuclear Station Is

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