ML20058N800

Requests Provision of Listed Info Prior to Restart of Units 1 & 3.Performance of PRA for Unit 2 in Manner That Takes Into Account Dependencies to Equipment Located in Other Two Units Also Requested

ML20058N800
Person / Time
Site:	Browns Ferry
Issue date:	08/13/1990
From:	Ross T Office of Nuclear Reactor Regulation
To:	Kingsley O TENNESSEE VALLEY AUTHORITY
References
GL-88-20, NUDOCS 9008150108
Download: ML20058N800 (4)

Text

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. UNITED 8 TATE 3 .l NUCLEAR REGULATORY COMMISSION r, WASHINGTON, D. C. 30566 ef

% , , #' August 13, 1990  !

Docket Hos. 50-259 f and 50-296 i

1 Mr. Oliver D. Kingsley, Jr. i Senior Vice President, Nuclear Power 2 Tennessee Valley Authority. 'l 6N 38A Lookout Place  ;

1101 Market Street i Chattanooga, Tennessee 37402-2801 ~

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Dear Mr. Kingsley:

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SUBJECT:

PRA CONCERNS REGARDING OPERATION OF BROWNS FERRY, UNITS 1 AND 3 All three units at Browns Ferry Nuclear (BFN) Plant share many important safety systems (e.g., diesel generators, RHR service water -

water, vital station batteries) and electrica' uses,(called" emergency equipment cooling boards"atBFN)..

• During restart efforts for Unit 2, it became c dnt that failures or inadvertant 4

operation of equipment in Units 1 and 3 could Mn sely affect Unit 2 safety; Therefore, TVA has committed (via technical spec G1 cations and administrative controls) to maintain certain equi '

operable (e.g., fire suppression) to pment thattheir assure is located in Units availability 1 and 3 safe to support either operation of Unit 2, or inoperable as necessary to preclude inadvertant operation 4

of these systems from jeopardizing the safe operation of Unit'2.

The NRC staff is concerned about the potential interactions among units at BFN, t some of which may be very subtle. There is significant sharing of safety-related equipment and the possibility exists that equipment failure or operator error at one unit could adversely affect the operation of other units. One way to examine for these interactions is through a probabilistic risk assessment (PRA), such as the study being performed by TVA as part of the Individual Plant Examination (IPE) of Generic Letter (GL) 88-20. However, traditional PRAs only model a plant se if it stood alone. Most PRAs have not extensively modeled or sought out interactions among units that may initiate new or unexpected events. >

The NRC staff has already requested that TVA complete a dependency matrix for l Unit 2 that will help determine the manner in which the diesel genarators, safety -

! systems, and support systems are interrelated. Because the three units at BFN are not symmetric with regard to electrical loads and other plant demands, it 'is important for TVA and NRC to understand the potential safety implications of the various operating modes for all units rather than just Unit 2 operating (e.g.,-(a) all three at 100 percent power, (b) Unit I at 100 percent power and  ;

Units 2 and 3 shutdown, (c) Units 1 and 3 at 100 percent' power and Unit 2. ,

i shutdown,etc.). However, without a good understanding of the interrelationships among the units (such as would be gained by having dependency tables for each of f

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2 the three units), it is very difficult to determine the inost risk significant  :

operating mode combinations for each/all of the BFN units. Consequently, the l staff is requesting TVA to provide the following information prior to restart i of Unit 1 or 3:

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1. Dependency tables for Units 1 and 3 similar to that requested for Unit 2 by letter dated June 6,1990. -

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2. Expanded IPEs for Units 1 and 3 that evaluate the entire site as a whole, taking into account the risk significant combinations of unit ,

operational status.

(Note, the staff has previously requested the Florida Power and Li l Company to perform a PRA (now being performed as part of thethat IPE) ght i simultaneously models Turkey Point Units 3 and 4, since there is >

significant sharing of safety systems between the two units.)

Furthermore, the staff requests that the PRA for the Unit 2 IPE be performed  ;

in a manner that takes into account the dependencies to equipment located in the other two units.  !

TVA should submit a schedule for providing the information above to the staff ,

within the next 60 days. If there are any questions or concerns regarding '

this request, please contact your NRC Project Manager. I Sincerely, I I

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Original signed by l Thierry M. Ross, Project Manager l Project Directorate 11 4 1 l Division of Reactor Projects - I/II I Office of Nuclear Reactor Regulation cc w/ enclosures:

See next page

• SEE PREVIOUS CONCURRENCE  !

! OFC :PDil.4/LA* :PDII.4/PM* :PDII-4/D*  :  :  :

MKrebs NAME :TRoss :FHebdon  :  :  :

DATE :8/13/90 :8/13/90 :8/13/90  :  :  :

0FFICIAL RECORD COPY Document Name: BFN PRA U1/3 j

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• k Mr. Oliver D. Kingsley, Jr. i cc-Mr. Marvin Runyon, Chairman Mr. O. J. Zeringue, Site Director i Tennessee Valley Authority Browns Ferry Nuclear Plant 1 ET 12A 7A Tennessee Valley Authority 400 West Summit Hill Drive P. O. Box 2000 Knoxville, Tennessee 37902 Decatur, Alabama 35602 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 SN 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 huclear Plant ET 12A 9A Tennessee Riiey Authority 400 West Summit Hill 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 128 16E Athens, Alabama 35611 l

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 l ET 11B 33H Knoxville, Tennessee 37902 Regional Administrator, Region II U.S. Nuclear Regulatory Commission Mr. Dwight Nunn 101 Marietta Street, N.W.

Vice President, Nuclear Engineering Atlanta, Georgia 30323 Tennessee Valley Authority 6N 38A ',ookout Place Mr. Charles Patterson 1101 Parket Street Senior Resident Inspector '

Chattanooga, Tennessee 37402-2801 Browns Ferry Nuclear Plant U.S. Nuclear Regulatory Cotamission Dr. Mark O. Medford Route 12, Box 637 Vice President and Nuclear Athens, Alabama 35611

[ Technical Director L Tennessee Valley Authority Tennessee Valley Authority 6N 38A Lookout Place Rockville Office Chattanooga, Tennessee 37402-2801 11921 Rockville Pike Suite 402 Rockville, Maryland 20852

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DISTRIBUTION

._ _ . _ . . g NRC PDR Local PDR S. Varga 14-E-4 ,

G. Lainas 14-H-3 i F 'Hebdon +

- S. Black B. Wilson R-II L. Reyes R-II W. S. Little R-II

' T Ross D. Moran OGC E. Jordan HNBB33-02 ACRS(10)

GPA/CA 17-A-3 l

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