ML20236A021

Discusses Grid Overvoltage Condition at Safety Buses Based on Util 890122 Notice of Failure of Diesel Generator 2A-A. NRC Insp Planned for Wk of 890424 to Assess Adequacy of Actions to Manage long-term Grid Overvoltage Conditions

ML20236A021
Person / Time
Site:	Sequoyah
Issue date:	03/07/1989
From:	Black S Office of Nuclear Reactor Regulation
To:	Kingsley O TENNESSEE VALLEY AUTHORITY
References
TAC-R00419, TAC-R00420, TAC-R419, TAC-R420, NUDOCS 8903160273
Download: ML20236A021 (3)

Text

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0 4 UNITED STATES ,

$2 j p, NUCLEAR REGULATORY COMMISSION L j. Wrs SHINGTON, D. C. 20555 .

,/ March 7, 1989  ;

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Docket Nos. 50-327/328 Mr. Oliver D. Kingsley, Jr.  !

Senior Vice President, Nuclear Power l I

Tennessee Valley Authority 6N 38A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801

SUBJECT:

GRID OVERV0LTAGE CONDITION AT SAFETY BUSES (TAC R00419, R00420) -

SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 On January 22, 1989, the Tennessee Valley Authority (TVA) informed the staff of the failure of Diesel Generator 2A-A to meet the overvoltage limit expected during the performance of load rejection testing conducted on January 21, 1989.

During this test, the voltage reached 8160V which is in excess of the maximum limit of 7866V specified in the Technical Specifications. It was TVA's determination, however, that this overvoltage condition resulted from an unacceptably high pretest diesel and grid voltage of 7400V at the shutdown boards and, therefore, the test was invalid.

Furthermore, TVA acknowledged that the high grid voltage had persisted for some time and was expected to continue for a few more weeks, and therefore, .c retesting could not be preformed until the voltage at the shutdown boards I returned to near normal 6900V, when large loads (i.e. Reactor Coolant pumps) <

are reconnected to the boards. P wever, further evaluation of.the test results by TVA determined that additional testing of Diesel Generator 2A-A for load rejection capability would not be required because the voltage reached during the initial test is bounded by the calculated maximum voltage that equipment can withstand during a transient voltage condition. We have reviewed TVA's evaluation and have concluded that the initial test is acceptable, as discussed in the staff's letter dated January 30, 1989 which issued amendments to the Sequoyah Technical Specifications on diesel generator testing.

However, staff concern over apparent lack of provisions to regulate anticipated long term grid overvoltage conditions has resulted in the need for reevaluation of TVA's commitments made in response to specific employees concerns, regarding 0FI i

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Mr. Oliver D.. Kingsley, Jr. management of grid overvoltage' conditions at Sequoyah. These connitments were i given in the Sequoyah Element Report OP-30202. We are, therefore planning to conduct an inspection at Sequoyah during the week of April 24, 1989 to assess the adequacy of provisions implemented for managing anticipated long-term grid overvoltage conditions at ,the site.

Sincerel.y, Original signed by Rajender Auluck for Suzanne Black, Assistant Director for Projects TVA Projects Division Office of Nuclear Reactor Regulation i

cc: See next page Distribution Docket File NRC PDR Local PDR i Projects Reading i ADSP Reading a D. Crutchfield ,

B. D. Liaw j

.S. Black

'R. Pierson F. McCoy M. Simms J. Donohew G. Hubbard .

J A. Marinos

'J. Rutberg l S. Varga B. Grimes E. Jordan ACRS (10)

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Mr. Oliver D. Kingsley, Jr. Sequoyah Nuclear Plant l cc: .

General Counsel Regional Administrator, Region II Tennessee Valley Authority U.S. Nuclear Regulatory Commission i 400 West Summit Hill Drive 101 Marietta Street, N.W. j E11 B33 ,

Atlanta, Georgia 30323 '

Knoxville, Tennessee 37902 Resident Inspector /Sequoyah NP Mr. R. L. . Gridley . c/o U.S. Nuclear Regulatory Comission

' Tennessee Valley Authority 2600 Igou Ferry Road 5N 157B Luokout Place Soddy Daisy, Tennessee 37379 Chattanooga, Tennessee 37402-2801 Mr. John T. LaPoint Mr. Michael H. Mobley, Director Tennessee Valley Authority Division of Radiological Health Sequoyah Nuclear Plant T.E.R.R.A. Building, 6th Floor P.O. Box 2000 150 9th Avenue North Soddy Daisy, Tennessee 37379 Nashville, Tennessee 37219-5404 Mr. M. Ray Dr. Henry Myers, Science Advisor Tennessee Valley Authority Committee on Interior Sequoyah Nuclear. Plant and Insular Affairs P.O. Box 2000 U.S. House of Representatives Soddy Daisy Tennessee 37379 Washington, D.C. 26515 Mr. D. L. Williams Tennessee Valley Authority Tennessee Valley Authority Rockville Office 400 West Summit Hill Drive 11921 Rockville Pike W10 885 Suite 402 Knoxville, Tennessee 37902 Rockville, Maryland 20852 County Judge Hamilton County Courthouse Chattanooga, Tennessee 37402 j l

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