ML19325E680

Responds to Item 11 of Generic Ltr 88-20, Individual Plant Exam for Severe Accident Vulnerabilities-10CFR50.54(f), Requesting Proposed Programs for Completing Individual Plant Exam.Overall Objectives of PRA Program Listed

ML19325E680
Person / Time
Site:	Beaver Valley
Issue date:	10/30/1989
From:	Sieber J DUQUESNE LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-NUREG-1335, RTR-NUREG-CR-2300 GL-88-20, NUDOCS 8911080250
Download: ML19325E680 (5)

Text

'

? 8

.- j

'k j,

n~',

a Va y Power Staten

.]

i

, SNoran0 port. PA 40776 )

l t

m  ;

t y .$, ,., og m2) 64n2M l October 30, 1989 l

(-

i

l. U. S.' Nuclear Regulatory Commission Attn: Document Control Desk i Washington, DC 20555 '

V

Reference:

- Beaver Valley Power Station, Unit No. 1 and No. 2 BV-1 Docket No. 50-334, License No. DPR-66 BV-2 Docket No. 50-412, License No. NPF-73  ;

$~ Generic Letter 88-20 Gentlemen: .

This letter is in response to the first part of Item 11 of Generic Letter No. 88-20, " Individual Plant Examination.for Severe o Accident Vulnerabilities -

10CFR50. 54 ( f) ", requesting the proposed 1 programs.for completing the Individual Plant Examination (IPE).  !

Duquesne Light Company will perform the Individual Plant  !

Examination for Beaver Valley Units 1 and 2 by developing separate Level 2 Probabilistic Risk Assessments (PRAs). The PRAs will meet or ,

exceed the requirements of examination method 1, described in Generic

• Letter 88-20 (the PRA option). The summary reports are scheduled for NRC submittal by September 29, 1991 for both units.

s The PRA is being performed by a . team of engineers and PRA specialists from Duquesne Light company (DLC); Pickard, Lowe and l Garrick, Inc. (PLG); and Stone & Webster Engineering Corporation l (SWEC). Beaver Valley Unit 2 is being studied first, with the PLG l and SWEC personnel leading the effort and transferring technology to  ;

I DLC personnel through formal training, on-the-j ob training, and [

l review of the task outputs. The Beaver Valley Unit 1 PRA is being developed by DLC personnel, with SWEC and PLG reviewing the work. ,

l ,

l The overall objectives of the PRA program are to:  ;

• Develop separate, plant-specific PRA's for Units 1 and 2 to support a comprehensive risk and accident management program.

• Apply and develop generic and plant-specific PRA databases for initiating event frequencies, component failure rates, maintenance unavailability, common cause failure parameters, and human error rates.

• Develop point estimate and uncertainty distribution results for the frequency of core damage and a full spectrum of radioactive release categories for Units 1 and 2.

b&

8911080250 891030 F ' t PDR ADOCK 05000334 R P PNU h

o Be vcr Vallcy P:wcr St0tien, Unit.NO3. 1&2 a' . Docket NQ. 50-334, License No. DPR-66 Docket No. 50-412, License No. NPF-73 i

Generic Letter 88-20 l Page 2

• Determine the underlying risk controlling factors, importance measures, and key sources of uncertainty in developing the risk estimates.

• Provide technology transfer to DLC, including methods, software and training in the use of PRA' methods, severe  ;

accident behavior, and application of associated computer ,

software.  ;

• Meet the NRC requirements for IPEs as set forth in Generic l

( Letter 88-20 and NUREG-1335. l The methodology used to develop the Beaver Valley PRA is a modern i extension of the PRA approach developed by PLG, incorporated into NUREG/CR-2300, and applied to a number of PRA projects that were ,

reviewed by the NRC. The most recent examples are those on Seabrook, Three Mile Island 1, Diablo Canyon, and the South Texas Project. The l key features of this approach are the use of event sequence diagrams ,

i to track the interactions.between the plant behavior and application of the emergency ~ operating procedures and the 'use of linked, -

modularized event trees to help quantify the' likelihood of these scenarios. All the event trees and faugg trees are developed, quantified, and analyzed with the RISKMAN Version 2 integrated software package. The system of linked event trees used to define i accident sequences for the Beaver Valley PRA is shown in Figure 1. ,

This model contains a large number of different seemedos that are systematically developed from the initiating event to the final j release result. L a

Systemic event trees are provided for the response of the support  :

systems (e.g., electric power, service water, etc.) and the front-line systems (e.g. auxiliary feedwater, quench spray, etc.).

Dependency matrices that are developed from a detailed examination of ,

all of the plant systems help to account for important interdependencies and interactions that are highly plant specific.

Event- sequence diagrams are used to incorporate operator actions from '

the emergency operating procedures into the frontline systems event trees and the operator recovery actions event tree. Human error rates are quantified using an application of the success likelihood index methodology. A detafled definition of plant damage states provides a clean interface oetween the Level 1 and Level 2 event '

trees.

Containment phenomena are examined in the containment event tree that is developed specifically for each unit. The evaluation of containment response is based in part on comparison with similar containments which have previously been studied (e.g., Surry in NUREG-1150). Requestod information on the timing and magnitude of a spectrum of radioactive releases is being developed from existing information on similar plants like Surry, supplemented as needed by plant specific analyses using the MAAP computer code.

1

• r ' , '

BOOvCr Vallcy P wcr Stctien, Unit Nc3. 1&2 l

.- Docket No. 50-334, License No. DPR-66 Docket No. 50-412, License No. NPF-73 Generic Letter 88-20 '

Page 3 l i

The systematic, structured approach that is followed in constructing the accident scenario models helps provide assurance j

that plant-specific features will be identified and that an appropriate degree of completeness will be achieved. It 'also provides. for the systematic, top-down development of engineering insights about the key risk controlling factors that drive the results. ,

1 The milestones and schedule for performing the IPEs are as follows:

• In 1988, the first phase of the Unit 2 PRA was completed. This '

phase included system familiarization, system description l preparation, reliability block diagrams, general transient event sequence diagrams, system dependency matrices, and a preliminary list of initiating events. The documentation resulting from this phase was reviewed by DLC Engineering, Operations and Licensing  ;

personnel to ensure accuracy and fidelity of the models in.

relation to as-built plant features and existing procedures.

• In 1989, we will complete a Level 2 PRA on Unit 2 using generic ,

PRA data. In parallel, a' team of DLC personnel with support and guidance from PLG and SWEC will complete the first phase of the PRA on Unit 1.

• In 1990, we will complete a Level 2 PRA on Unit 1 and develop a plant-specific PRA database based on a total of almost 15 reactor-years of BVPS Unit 1 and 2 operating experience.

• Prior to the IPE submittal in 1991, DLC will requantify both the Unit 1 and Unit 2 PRA models to incorporate plant-specific data.

This submittal will include the evaluations of vulnerabilities and candidate changes to plant design and operation that result from these plant examinations.

Very truly yours, J.

~( D. l W Sieber FVice President Nuclear Group cc: Mr. J. Beall, Sr. Resident Inspector Mr. W. T. Russell, NRC Region I Administrator Mr. P. Tam, Sr. Project Manager Mr. J. J. Carey Mr. R. Saunders (VEPCO)

r E !t

\(

9 * . 4r ei j 5W~

_ g1 i- I r

.@ ,!!e

, e l

_ t "

- t t gi i

Een rgI t

$lu t \ r t Wi iinl

_ !r t Er " t$- l t t ls!f,,

! I- E f~s

!es  !. . t ll t ll!9 sw i / N t sE j I

- t

.h t t Er

l8 t t t t h w , '

lr[- lln

.! al 1e rl El

! a , .

a af -

-  : . '  ! . 't ~ I i ;

r. .

.=

e .

k ,

COMMONWEALTH OF PENNSYLVANIA)

) ss:

COUNTY OF BEAVER- )

,e J ,. :

fE

/' Nk e) on this t day of -

v 7M4_ - , 1989, before me, J2/// d.2J1 a Notary Public in and'for said fj t/

Commonwealth and tounty, personally appeared J. D. Sieber, who being duly sworn, deposed, and said that (1) he is Vice-President of Duquesne Light, (2) he is duly authorized to execute and file the foregoing Submittal on behalf of said Company, and (3) the' statements set forth in the Submittal are true and correct to the best of his knowledge, information and belief.

l k Abl/ ._ (LdA1 l

// v NotarialSeal e O CQ MyComnetJon Expres Ato 16, twa -

Member.Pemsytem Assodanon d Notne l

-  ;