ML20081K095

Ro:On 831015-16,w/Unit 1 Out of Svc,Standby Bus 2 Deenergized to Allow Operability Verification of Underground Emergency Power Path in Accordance W/Tech Specs.On 831015, CT-3 Underwent Lockout.Caused by Bad Insulators

ML20081K095
Person / Time
Site:	Oconee
Issue date:	11/01/1983
From:	Tucker H DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 8311090252
Download: ML20081K095 (2)

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O DUKE POWER GOMPANY P.O. BOX 33180 CHAHLOTTE, N.C. 28242 HALB. TUCKER TELEPldONE

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= = = ' - = = November 1, 1983 ggyy 4g.24 Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region 11 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303 Re: Oconee, Nuclear Station Docket Nos. 50-269, -270, -287

Dear Mr. O'Reilly:

Please find attached a Special 5-Day Report concerning the deenergization of one of Oconee's standby buses to allow for operability verification of the underground emergency power path, with Keowee Unit 1 out of service. This report is submitted pursuant to Oconee Nuclear Station Technical Specification 3.7.9 and describes an. incident which is considered to be of no significance with respect to its effect on the health and safety of the public.

Very truly yours,

!M Hal B. Tucker JCP/php Attachment cc: Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555 INPO Records Center Suite 1500 1100 Circle 75 'arkway Atlanta, Georgia 30339 Mr. J. C. Bryant NRC Resident Inspector Oconee Nuclear Station Mr. John F. Suermann Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 y^ c~Cb 831109025 '

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JP0/HBT/JCP November 1, 1983 Duke Power Company Oconee Nuclear Station Special Report Deenergization of Oconee Standby Bus 2 to Allow for Operability Verification of the Underground Emergency Power Path While Keawee Unit 1 Was Out of Service On October 15 and 16, 1983, with Keowee Unit 1 out of service for planned maintenance and Keowee Unit 2 available, Lee "6C" Gas Turbine was being used to energire both Oconee 4160V Standby Buses as required by Technical Specifica-

, tion 3.7.4. At 1449 and 2156 hours0.025 days <br />0.599 hours <br />0.00356 weeks <br />8.20358e-4 months <br /> on October 15, and 0545 hours0.00631 days <br />0.151 hours <br />9.011243e-4 weeks <br />2.073725e-4 months <br /> on October 16, 1 Standby Bus 2 was deenergized to allow operability verification of the under-ground emergency power path in accordance with Technical Specificatio.n 3.7.2.

At 1349 hours0.0156 days <br />0.375 hours <br />0.00223 weeks <br />5.132945e-4 months <br /> on October 15, 1983, CT-3 (Unit 3 Startup Transformer) underwent a lockout. The apparent cause of the lockout was bad insulators in a location which made both CT-3 and an alternate startup transformer unavailable to supply power to the Unit 3 Main Feeder Buses.

If both Keowee hydro units had been available at the time of the CT-3 lockout.

Technical Specification 3.7.2(a) would have applied since the lockout would cause the overhead emergency power path from a Keowee hydro unit to Unit 3 to be unavailable. The requirements of Technical Specification 3.7.2(a) include verifying operable the underground emergency power path by energizing at least one standby bus from a Keowee hydro unit within one hour and every eight hours thereafter. Since one standby bus could not be energized from Keowee and still have both standby buses continuously energized from Lee, personnel interpreted the situation conservatively and requested that the underground emergency power path be verified operable in accordance with Technical Specifica-tion 3.7.2. This verification required one of the standby buses to be deenergized from Lee and placed the two operating Oconee units in a degraded mode beyond that allowed by Technical Specification 3.7.4.a. This incident is reportable to the Nuclear Regulatory Commission in accordance with Technical Specification 3.7.9.

A safety evaluation was performed pursuant to Technical Specification 3.7.9 and the decision was made that allowed continued operation of the units since one standby bus and the Keowee underground feeder were always available during the tests for operability. The total time that Oconee had only one standby bus energized from Lee Steam Station was less than four (4) minutes.

At the time of the tests, Lee "6C" Gas Turbine was still providing power to the Oconee standby buses via the 100 KV transmission line and,in addition, emergency power was available from Keowee via the underground feeder. Also available was the normal Duke Power Company transmission system to the 230 KV switchyard via at least two 230 KV transmission lines on separate towers. The probability of losing offsite power during this testing is very small; therefore, the health and safety of the public were not endangered.