ML20028H382

Forwards Success Criteria for Dominant Sequences Leading to Core Damage at Facility

ML20028H382
Person / Time
Site:	Browns Ferry
Issue date:	12/26/1990
From:	Ross T Office of Nuclear Reactor Regulation
To:	Kingsley O TENNESSEE VALLEY AUTHORITY
References
TAC-77743, NUDOCS 9101020205
Download: ML20028H382 (5)

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UNITED STATES

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December 26, 1990 Docket No. 50-260 i

Mr. Oliver D. Kingsley, Jr.

Senior Vice President, Nuclear Power Tennessee Valley Authority 6N 38A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801

SUBJECT:

SUCCESS CRITE9IA FOR DOMINANT SEQUENCES LEADING TO CORE DAMAGE AT BROWNS FERF.Y NUCLEAR PLANT UNIT 2 - (TAC 77743)

By letter dated June 6,1990, we requested that the Tennessee Valley Authority (TVA) provide a dependency matrix for important front-line and support systems at Browns Ferry, Unit 2.

This request was prompted by the need for six of the eight emergency diesel generators on the site to be maintained under Technical Specification control in order to restart Unit 2.

On October 1,1990, TVA submitted dependency matrices for support system to support system and front-line to support system dependencies. We have now determined that we need the success criteria for dominant core damage sequences at Browns Ferry, Unit 2 in order to complete our evaluation.

1 Our initial review of these matrices has not uncovered any dependencies or apparent problems of L magnitude that should preclude restart of Unit 2.

How-ever, to allow us to complete a more thorough evaluation of potential depen-dency problems caused by the need for six diesel generators, we are requesting TVA to supply success criteria for core damage dominant sequences.

We have enclosed a list of dominant sequences for a BWR 4 Mark 1 based on review of the Peach Bottom and Brunswick Probabilistic Risk Assessments (PRt.s).

We have also provided a sample of the degree of detail that we would like to receive when TVA responds to our request for the Browns Ferry, Unit 2 success

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criteria. Wherever possible, we urge TVA to provide the staff with "best estimates" rather than the explicit success criteria contained in the Final Safety Analysis Report (FSAR).

This is to eliminate unnecessary conservatisms from a PRA perspective.

Furthermore, TVA is requested to provide us with this information within ninety days from receipt of this letter, 9101020205 901226 PDR ADOCK 05000260 1

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' M'c. ' live r D. 'Kingsley, J r. O If you have any questions regarding this request for additional information, please contact me at (301) 4921313.

The reporting and/or recordkeeping requirements contained in this letter are fewer than ten respondents; therefore, OMB clearance is not required under P.L. 96 511.

Sincerely, Original signed by On ic d. Moran for Thierry M. Ross, Project Manager Project Directorate 114 Division of Reactor Projects - 1/11 Office of Nuclear Reactor Regulation

Enclosures:

1.

Dominant Sequences for BWR.4 2.

Example Success Criteria cc w/ enclosures:

See next page Distribution bocket File NRC PDR Local PDR S. Varga 14-E-4 G. Lainas 14 -H.3 F. Hebdon S. Black B. Wilson Ril P. Kellogg RII C. Patterson Ril M. Krebs T. Ross D. Moran B. Mozafari OGC 15-B-18 E. Jordan MNBB-3701 ACRS(10)

BFN Rdg. File

• SEE PREVIOUS CONCURRENCE

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OFFICIAL RECORD COPY Document Name: SUCCESS CRITERIA

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ENCLOSURE 2 EXAMPLE OF SUCCESS CRITERIA ATWS WITH MSIV CLOSURE 1

Suberiticality Recirculation pump trip and SLCS or Manual scram successful Coolant Makeup HPCI

.or 2/7 ADS valves and 1/2 core _ spray trains or-2/7 ADS valves and 1/4 LPCI pumps Containment-Protection Control water level throughout' transient and Depressurize at HCTL 0; cay Heat Removal 1/2-RHR heat exchangers'(with associated service water-system-train) in shutdown fcooling mode -

-of 11/21RHR heat exchangers (with associated-service water

system train) in suppression pool cooling: mode.

or Containment venting with CRD or condensate

-or.

-Turbine bypass-and-condenser operable _(MSIV reopening and PCS -recovery) with feedwater condensate, CRD/HPCI/RCIC with transfer of condensate-to condensate storage tanks or LPCI/CS with suppression pool makeup from various sources.

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ENCLOSURE 1 DOMINANT SEQUENCES FOR A BWR 4 MARK 1 Loss of offsite power Transients with subsequent stuck open safety relief valve (s)

ATWS with MSIV closure ATWS MSIY closure Turbine trip Small LOCA Intermediate LOCA Steamline break Transient with power conversion initially unavailable Transient with loss of feedwater Large LOCA

Mr. Oliver D. Kingsley, Jr.

CC:

Mr. Marvin Runyon, Chairman Mr. O. J. Zeringue, Site Director Tennessee Valley Authority Browns Ferry Nuclear Plant ET 12A 7A Tennessee Valley Authority 400 West Summit Hill Drive P. O. Box 2000 j

Knoxville, Tennessee 37902 Decatur, Alabama 35602 j

Mr. Edward G. Wallace Mr. P. Carier, Site Licensing Manager Manager, Nuclear Licensing Browns Ferry Nuclear Plant and Regulatory Affairs Tennessee Valley Authority Tennessee Valley Authority P. O. Box 2000 5N 157B Lookout Place Decatur, Alabama 35602 Chattanooga, Tennessee 37402-2801 Mr. John B. Waters, Director Mr. L. W. Myers, Plant Manager Tennessee Valley Authority Browns Ferry Nuclear Plant ET 12A 9A Tennessee Valley Authority 400 West Sumit Mill Drive P. O. Box 2000 Knoxville, Tennessee 37902 Decatur, Alabama 35602 Mr. W. F. Willis Chairman, Limestone County Commission Chief Operating Officer P. O. Box 188 ET 12B 16B Athens, Alabama 35611 400 West Summit Hill Drive Knoxville, Tennessee 37902 Claude Earl Fox, M.D.

State Health Officer General Counsel State Department of Public Health Tennessee Valley Authority State Office Building 400 West Summit Hill Drive Montgomery, Alabama 36130 ET 118 33H Knoxville, Tennessee 37902 Regional Administrator, Region II U.S. Nuclear Regulatory Commission Mr. Dwight Nunn 101 Marietta Street, N.W.

Vice President, Nuclear Projects Atlanta, Georgia 30323 Tennessee Valley Authority 6N 38A Lookout Place Mr. Charles Patterson 1101 Market Street Senior Resident Inspector Chattanooga, Tennessee 37402-2801 Browns Ferry Nuclear Plant U.S. Nuclear Regulatory Comission Dr. Mark 0. Medford Route 12 Box 637 Vice President, Nuclear Assurance, Athens, Alabama 35611 Licensing and Fuels Tennessee Valley Authority Tennessee Valley Authority 6N 38A Lookout Place Pockville Office Chattanooga, Tennessee 37402-2801 11921 Rockville Pike Suite 402 Rockville, Maryland 20852