ML20133L112

Forwards RAI Re Reliability of Offsite Power Grid at Plant. Requested Info Should Be Provided by Licensee within 60 Days of Receipt of Ltr

ML20133L112
Person / Time
Site:	Sequoyah
Issue date:	01/17/1997
From:	Hernan R NRC (Affiliation Not Assigned)
To:	Kingsley O TENNESSEE VALLEY AUTHORITY
References
TAC-M93319, TAC-M93320, NUDOCS 9701210489
Download: ML20133L112 (4)

Text

,

e )

January 17, 1997 Mr. Oliver D. Kingsley, Jr. Distribution President, TVA Nuclear and Docket File PUBLIC Chief Nuclear Officer SQN Rdg. SVarga Tennessee Valley Authority JZwolinski 0GC 6A Lookout Place ACRS EMerschoff, RIl 1101 Market Street Chattanooga, TN 37402-2801

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION - RELIABILITY OF 0FFSITE POWER SYSTEM - SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 (TAC NOS. M93319 AND M93320)

Dear Mr. Kingsley:

The Nuclear Regulatory Commission (NRC) staff, with technical assistance from its contractor, Scientech, Inc., has reviewed and evaluated information provided by NRC Region II, and by the Tennessee Valley Authority (TVA) in response to a request from Region II regarding the reliability of the offsite power grid at the Sequoyah Nuclear Plant. The staff's concerns were discussed in NRC Inspection Report 50-327, 328/93-02 and in a letter to TVA requesting information dated March 27, 1996. TVA's response to that letter was dated July 17, 1996.

In order to resolve the staff's concern, we have determined that additional information is needed. We therefore request that the information requested in the enclosure be provided by TVA within 60 days of receipt of this letter.

Please contact me at (301) 415-2010 if you have any questions.

Sincerely, Original signed by Ronald W. Hernan, Sr. Project Manager Project Directorate 11-3 Di+:sion of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket Nos. 50-327 and 50-328

Enclosure:

Request for Additional Information cc w/ enclosure: See next page DOCUMENT NAME: SQN\93319.RAI To receive a copy of this doctment, indicate in the box:

"C" = Copy without attachment / enclosure "E" = Copy with attachment / enclosure "N" = No copy 0FFICE PDII-3/PMA , PDII-3/LA l) PDII-3/PD,1 lC I NAME RHernan ji f BCl ayton /S FHebdon 4d s g DATE 1/)7/97' 1/16/97 1/ n /97 0FFICIAL RECORD COPY 9701210489 970117 PDR ADOCK 05000327 P PDR

, t Mr. Oliver D. Kingsley, Jr. SEQUOYAH NUCLEAR PLANT Tennessee Valley Authority cc:

Mr. O. J. Zeringue, Sr. Vice President Mr. J. T. Herron, Plant Manager Nuclear Operations Sequoyah Nuclear Plant Tennessee Valley Authority Tennessee Valley Authority 6A Lookout Place P.O. Box 2000 1101 Market Street Soddy Daisy, TN 37379 l Chattanooga, TN 37402-2801 l Regional Administrator l Mr. Mark 0. Medford, Vice President U.S. Nuclear Regulatory Connission  ;

Engineering & Technical Services Region II '

Tennessee Valley Authority 101 Marietta Street, NW., Suite 2900 6A Lookout Place Atlanta, GA 30323 1101 Market Street Chattanooga, TN 37402-2801 Nr. Melvin C. Shannon Senior Resident Inspector Mr. R. J. Adney, Site Vice President Sequoyah Nuclear Plant Sequoyah Nuclear Plant U.S. Nuclear Regulatory Connission ,

Tennessee Valley Authority 2600 Igou Ferry Road P.O. Box 2000 Soddy Daisy, TN 37379 l Soddy Daisy, TN 37379 l Mr. Michael H. Mobley, Director l General Counsel Division of Radiological Health l Tennessee Valley Authority 3rd Floor, L and C Annex ET 10H 401 Church Street 400 West Sunnit Hill Drive Nashville, TN 37243-1532 Knoxville, TN 37902 County Executive l Mr. Raul R. Baron, General Manager Hamilton County Courthouse Nuclear Assurance and Licensing Chattanooga, TN 37402-2801 Tennessee Valley Authority 4J Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801 Mr. Pedro Salas, Manager l Licensing and Industry Affairs

, Tennessee Valley Authority 4J Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801

- Mr. Ralph H. Shell, Manager Licensing and Industry Affairs l Sequoyah Nuclear Plant

Tennessee Valley Authority

P.O. Box 2000

Soddy Daisy, TN 37379

REQUEST FOR ADDITIONAL INFORMATION TENNESSEE VALLEY AUTHORITY SE000YAH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NUNBERS 50-327. 50-328 The Region II request for assistance was assigned Task Interface Agreement (TIA)94-021. Region II specifically requested that this review include answers to the following questions:

Based on the new Sequoyah Nuclear Plant (SQN) Transmission System Study and the new Common Station Service Transformers, does the plant have an acceptable immediate preferred offsite power source if the 500 kV to 161 kV intertie transformer is not operable? Does the 161 kV analysis demonstrate that the plant can achieve safe shutdown without the intertie transformer?

Should the plant's technical specifications be amended to require that LCO 3.8.1.1, Action C, be entered following a loss of the intertie transformer?

The design basis for immediate access offsite circuits i.as been stated as follows on page 8.2-16 of the Sequoyah Updated Final Safety Analysis Report.

One of the two circuits supplying electric power from the transmission network to the onsite electric distribution system "shall be designed to be available within a few seconds following j a loss-of-coolant accident to assure that core cooling, '

containment integrity, and other vital safety functions are maintained."

In addition, the licensing basis for the immediate access offsite circuits has been stated as follows on page 8.2-19 of the Sequoyah Updated Final Safety Analysis Report. ,

In the event of a LOCA on one generating unit and a simultaneous full load rejection by the other generating unit while one CSSTR (common station service transformer) is out of service, the two remaining CSSTR[s] will supply power to the emergency loads on the LOCA unit and to those loads on both units associated with norn;al operation which are not automatically tripped. ... All loads on both 6900-volt shutdown boards which start automatically are assumed to start simultaneously.

1. Analysis of immediate access offsite circuit Provide results of analysis (with reference to analysis calculations) or other justification for the followina defined desian basis events and assumptions. Analysis (or other justification) should demonstrate that the immediate access offsite circuit (s) from the transmission network to the Sequoyah facility will remain connected to safety system loads as

2 their source of power following postulated design basis events for all analyzed transmission network operating configurations. The analysis (or other justification) must demonstrate that voltage at the safety buses: (1) will not go below 5520 volts for greater than I second; or (2) will not go below 6456 volts without recovery to a voltage abova 6595.5 volts within 7.5 seconds (i.e., the offsite circuits will not be tripped by under voltage protective relays) due to transient voltages on the safety buses.

Desian Basis Events

• Unit 2 LOCA with simultaneous trip of Unit I and 2 and with simultaneous automatic start of all required design loads on both units in accordance to design and licensing basis requirements defined above.

• Unit 1 LOCA with simultaneous trip of Unit 1 and 2 and with simultaneous automatic start of all required design loads on both units in accordance to design and licensing basis requirements defined above.

Assumotions The transmission network operating at its worst case configuration such as with the transmission network at its highest projected peak loading, the 161 to 500 kV intertie transformer out of service, the automatic load tap changers on the CSSTRs out of service, one of the three CSSTRs out of service, all other devices on the transmission network (which may be required to change position following the LOCA and unit trip such as automatic connection of capacitor banks) out of service, other transmission system components (such as generating stations or transmission lines) out of service, all combinations of transmission network configurations as applicable, etc.

2. Describe the process which assures the Sequoyah control room operational staff that the transmission network is operating within analyzed parameters and that the immediate offsite power circuits to the Sequoyah plant are operable and will remain available following a LOCA.

I i

l l

!