ML20063C381

Forwards Revision 3 to Probabilistic Risk Assessment,In Response to NRC

ML20063C381
Person / Time
Site:	Limerick
Issue date:	04/30/1982
From:	Bradley E PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Tedesco R Office of Nuclear Reactor Regulation
Shared Package
ML20063C383	List: ML20063C381 ML20063C388
References
RTR-NUREG-0460, RTR-NUREG-0737, RTR-NUREG-460, RTR-NUREG-737, TASK-2.K.3.02, TASK-TM NUDOCS 8205040741
Download: ML20063C381 (2)

Text

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. PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 1881 -1981 PHILADELPHIA. PA.19101 EDWARD G. BAUER, JR.

(215)841-4000 D GENE AL QUNSEL EUGENE J. BRADLEY ASSOCIATE GENERAL COUNSEL DONALD BLANKEN l'UDOLPH A. CHILLEMI

{ 1 *,',"n*c"n*Co,n ,tt April 30, 1982 AS$1STANT GEN RAL COUNSEL EDWARD J. CULLEN. JR. __

JOHN F. KENNEDY. JR.

A2SISTANT COUNSEL Mr. Robert L. Tedesco, Assistant Director s f

United States Nuclear Regulatory Canmission Division of Line.nsing NUCSRQ:9 }

Office of Nuclear Reactor Regulation y f,py g T I982 %

Washington, D. C. 20555 g n I::aa gg ,/ g ra }- s Re: Limerick Generating Station Units 1 and 2 g G Docket Nos. 50-352 and 50-353 6

Dear Mr. Tedesco:

In response to the January 18, 1982 letter fran A. Schwencer to E.

G. Bauer, Jr. we have prepared a revision to the Prchabilistic Risk Assesment for Limerick Generating Station. The attached statemnt provides an overview of this revision. 'Ihere are enclosed 50 sets of revised pages for the Prcbabilistic Risk Assessmnt.

Pursuant to previous requests, we will serd sets of the revised pages to Sandia Natialal Laboratory, Brookhaven National Laboratory, the Chairman of the Board of Supervisors of Linerick Township, Region III of '

the United States Enviromental Protection Agency, the Pennsylvania Department of Envirormental Resources, and the Nuclear Regulatory Can-mission resident inspector at Linerick.

Very truly yours, Eu. ne r EJB/dq cc: See attached list -

with Enclosures

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'}

F205040741 82043o PDR ADOCK 05000352 b I (O  ;

A PDR i

l .

cc: ' Judge Lawrence Brenner Judge Richard F. Cole Judge Petei- A. Morris Troy B. Conner, Jr. , Esq. .

Stephen H. Lewis, Esq.

Mr. Frank R. Romano Mr. Charles B. Taylor Mr. Robert L. Anthony f Mr. Marvin I. Lewis Samuel & Clarissa B. Cooper Judith A. Dorsey, Esq.

Charles W. Elliot,t, Esq.

Mr. William Lochstet Mr. Alan J. Nogee l Mr. Steven Levin Robert W. Adler, Esq.

Mr. Thomas Gerusky Director, Pennsylvania Emergency Management Agency John Shniper, Esq.

S teven P. Hershey l James M. Neill, Esq.

Donald S. Bronstein, Esq.

Mr. Joseph H. White, III Dr. Judith H. Johnsrud Walter W. Cohen, Esq.

Robert J. Sugarman, Esq.

Mr. W. Wilson Goode Atomic Safety and Licensing, Appeal Panel Acomic Safety and Licensing Board Pane 1 Docketing and Service Sec cion i

i 9

\

l l

e LIMERICK TNERATING STATION PROBABILISTIC RISK ASSESSMENT REVISION A. Introduction The January 18, 1982 letter frm A. Schwencer to E. G. Bauer, Jr.

requested that Philadelphia Electric Conpany inform the NRC of plant design nodifications which would significantly affect the PRA and an assessment of those changes. The baseline for the PRA submitted -

on March 17, 1981 reflects syttm representations consistent with the design baseline as it eKisted in May,1980 (the initiation of the PRA). He have revised that baseline against the bamline consistent with January,1982 and have revised the PRA accordingly.

The revision in this submittal represents that baseline and will be usal to evaluate any future nodifications for tMir PRA significance.

Any future changes which are assessed to cumulatively effect an '

upward increase in core melt frequency by a factor of five will be reported to the NRC as a PRA revision ccnsistent with the January 18, 1982 letter frm A. Schwencer to E. G. Bauer, Jr.

B. Discussion of Changes Although all systes were revised, the significant changes in this revision are in the SIC, ADS, and RHR systens and the deleticn of COR. A sunstery of the revisions is as follows:

1. SIC (Stancby Liquid Control) he LGS SIC design was not sufficiently advanced at the time of the PRA to permit a plant specific representation.

For the PRA, AIMS the Alternate 3A as described in NUREG-0460 was used. The LGS specific design, as of thu date, is the Alternate 3A as described in NUREG-0460 but w?11 include autmatic start of three SIC punps instead of two punps and ability for independent loop testing to provide for improved overall reliability.

2. ADS (Autohatic Depressurization Systen) Effect on Low Pressure Systens The LGS design has been nodified primarily in the ADS air supply. The changes incorporate systs irprovements inplemented as a result of NUREG-0737 Iten II.k.3.2B and other system reliability reviss. These changes inprove low pressure systm success.

3. RHR (Residual Heat Removal)

The RHR systen included in t[his revision incorporates a more cmprehensive representation which reflects the availability of the systen with respect to pressurized and depressurized reactor conditions and service water cross ties. Those success paths which apply to sme but not all events have also been included to reflect more accurately the flexibility of the systen. The various operating nodes of the systen have been incorporated into ccrposite trees which better reflect the nature of the system.

4. CDR (Containnent Overpressure Relief)

Deleted, found to be unnecessary due to other systs '

inprovements included in this analysis.

C. Comparison of Results

1. Pault Trees Unavailability Systm 3/81 4/82 HPCI 9.6 x 10 -2 7.1 x 10

-2

-2 RCIC 7.8 x 10- 6.5 x 10 LICI 1.7 x 10- 1.8 x 10-LICS 6.2 x 10- 2.6 x 10-

-4 SIC 4.0 x 10- 9.0 x 10

-5 Electric Power 2.9 x 10 4.7 x 10-EEN 2.4 x 10 -5 7.1 x 10

-6 6.5 x 10 -3 ADS 6.6 x 10 RHR 3.9 x 10 -4 9.8 x 10-6 (Reactor Pressurized)

RHR 8.5 x 10-6 (Reactor Depressurized)

-1 Feedwater 2.9 x 10 7.'2 x 10-4*

• The fecdwater systs previously included loss of power and MSIV closure prcbabilities.

'Ihese prcbabilities are ncw included at the functional fault tree level because of unique event dependent.ies.

2. Core Melt Frequency (per year)

Class I II III IV 1.3 x 10 -5 1.4 x 10 -6 1.3 x 10 -7 3/81 8.5 x 10 1.2 x 10-5 9.6 x 10 1.1 x 10-6 1.3 x 10 -7 4/82

,