ML20083L541

Provides Comments Re PRA as Discussed at 840330 Meeting for Inclusion in Staff Rept on Risk Associated W/Facility. Related Correspondence

ML20083L541
Person / Time
Site:	Limerick
Issue date:	04/16/1984
From:	Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Schwencer A Office of Nuclear Reactor Regulation
References
OL, NUDOCS 8404170281
Download: ML20083L541 (4)

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DOCKETED PHILADELPHIA ELECTRIC COMPANYE 2301 MARKET STREET 1

'84 APR 16 P1 :43 P.O. BOX 8699 PHILADELPHIA. PA.19101

. rice OF SECFEiu.

ghgf,hD 215 841-45o2 JOHN S. MEMPER vecE+RES4 DENT gnsengEnema ano RESE ARCM Mr. A. Schwencer, Chief Docket Nos: 50-352 Licensing Branch No. 2 50-353 Division of Licensing U.S. Nuclear Regulatory Comnission Washington, DC 20555

Subject:

Limerick Generating Station, Units 1 and 2 Risk Asmssment

Reference:

Meeting between NRC Staff and Philadelphia Electric on March 30, 1984

Dear Mr. Schwencer:

At the reference meeting Mr. F. Rowsme informed us that the NBC Staff is writing a report sumnarizing the Staff's inquiry into the risk associated with Limerick. Mr. Rowsme invited Philadalphia Electric to provide conments by April 20, 1984, on the topics di e inaad at the reference meeting so that adequate time would be available to incorporate the cm ments, t

'Iberefore, with regards to the insights you have gained frcan your review of the probablistic risk assessment and the suggestions proposed for consideration at the reference meeting, we offer the following:

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1.

Reactor Manual Depressurization

'Ihe inportance of manually depra== Wing the reactor for certain transient and accident events has been recognized in the Limerick Transient Response T=plamantation Plan (T.R.I.P.)

Prmadees. Within these gc-> hes explicit instructions are provided to the operator to tell him under what conditions manual depressurization is required and to provide appropriate guidance' on performing this depressurization. The operators have received extensive training in the use of these gc-#ms on the T3marick sinnator.

8404170281 840416 PDR ADOCK 05000352 A

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'Ihe low probability events for which manual depressurization is required are transients and accidents that do not directly provide a high drywell pressure signal and which are further i

degraded by a loss of all high pressure make up. systems

'Ibese l

events are slow developing,' well understood transients which allow the operator sufficient time (at least 30 to 40 nuinutes on l

a worst case basis) to take the appropriate actions. 'mus, we consider the current design to be ada? mte.

i However, in response to NUREG-0737, Item II.K.3.18 we huve conmitted to more fully automate the depressurization function l

l such that manual depressurization will no longer be recluired for these events. 'Ihis will be am-lished by adding a bypass timer i

to the ADS logic such that the high drywell pressure initiation signal will no longer be required in the presence of a sustained i

reactor low water level signal. Also included.in this design is the addition of an ADS manual inhibit feature to facilitate override of the ADS logic for events where depressurimmeion is i

not warranted. Specific instructions will be included in the

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trip procedures on the use of this feature.

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In recognition of the Staff's view of the inportance of this i

item, we have agreed to inplement these changes on an accelerated schedule such that these modifications will be in place prior to

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fuel load.

2.

HPCI/BCIC Roca Cooling In the analysis of the loss of offsitd power initiator in the i

Limerick PRA, the various dependencies of the HPCI and EIC i

systems were considered. One of the dczninant contributors to the unavaimility of these systems for a loss of offsite power event is the failure of the diesel generators to supply power. Pbr g

this low probability event, the HPCI and RCIC systems would continue to operate off their DC power supplies, however, roca cooling for the HPCI and RCIC m m ts would be lost'.

In recognition of the dependencies of these systems ort the j

cooling function, preliminary calm 1=tions were parfar==ad to demonstrate that natural circulation cooling could be established by opening the===wt doors such that the time available tc6 repair the diesels or restore offsite power is signi4'imtly incranaarl. 'Ihe analysis demonstrated the effectiveness of this alternate cooling method without the need for forced circulation.

i We are currently in the process of dev=1 4

T =y the nocomaary gc-: " mas to mitigate this type of event and as pert caf this effort will review the original malemlations to verify that the conclusions are still valid and that forced circulation is not i

required.

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Containment Sprays' i

The importance of this function of the residual heat removal system has been recognized by the industry in the development of the Emergency Procedure Gti alines. '1he Limerick T.R.I.P.

PrMwes make extensive use of the conhimant sprays within the Containment Control Guidelines to limit pressura in both the drywell and the wetwell. Given the extensive operhtor training in these procedures, proper operation of the system to delay or prevent containment failure is assured.

The availability of the containment sprays is assured by demonstrating its cperability through periodic testing. Many of the wwets required to function in the containment spray node of the RER system are also required to function in its shutdown cooling, suppression pool cooling and low pressure injection nodes. A review of the surveillance testing requirements for the RHR system indicates that operability of the containment spray mode is denonstrated approximately once a month.

Philadelphia Electric is pleased to provide this information.

Mr. J. Phillabaum has coordinated this effort for us and should be contacted at (215)841-4766 if clarification or additional discussion of the subject is desired.

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Sincerely, I

i Skl

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Copy to:

Sco attached service list 9

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p cca Judge Lawrence Brenner Judge Peter A. Morris Judge Richard F. Cole Troy B. Conner, Jr., Esq.

Ann P. Hodgdon, Esq.

Mr. Frank R. Pcmano Mr. Robert L. Anthony Mr. Marvin I. Iaiis Charles W. Elliot, Esq.

Zori G. Ferkin, Esq.

Mr. 'Ihcznas Gerusky Director, Penna. Emergency Management Agency Mr. Steven P. Ilershey Angus Inve, Esq.

Mr. Joseph H. White, III David Wersen, Esq.

Robert J. Sugazman, Esq.

Spence W. Perry, Esq.

Jay M. Gutierrez, Esq.

Atcznic Safety & Licensing Appeal Board Atomic Safety & Licensing Board Panel Docket & Service Section Martha W. Bush, Esq.

James Wiggins Mr. Timothy R. S. Canpbell Phyllis Zitzer

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