ML20083M235
| ML20083M235 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 04/11/1984 |
| From: | Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8404170530 | |
| Download: ML20083M235 (4) | |
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PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHI A. PA.19101 JOHN S. KEMPER VICE PRESIDE NT e mesomaa a:NG Asso mass ances Mr. A. Schwencer, Chief Docket Nos: 50-352 Licensing Branch No. 2 50-353 Division of. Licensing U.S. Nuclear Regulatory Carmission Washington, DC 20555
Subject:
Lincrick Generating Station, Units 1 and 2 Risk Assesrcent
Reference:
Meeting betwwn NFC Staff and Philadelphia Electric on March 30, 1984
Dear Mr. Schwencer:
At the reference meeting Mr. F. Rowsme inforned us that the NRC Staff is writing a report sunmarizing the Staff's inquiry into the risk associated with Lhnerick. Mr. Rauscxte invited Philadelphia Electric to provide ccmrents by April 20, 1984, on the topics discussed at the reference meeting so that adequate time would be available to incorporate the cm ments.
Therefore, with regards to the insights.you have gained frca your review of the probablistic risk assessment and the suggestions proposed for consideration at the reference meeting, we offer the following:
1.
Reactor Manual Depressurization The inportance of manually depressurizing the react;
%r certain transient and accident events has been recogni eu in the Limerick Transient Response Inplementation Plan (T.R.I.P.)
Procedures. Within these procedures 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 procedures on the Limerick sinulator.
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h lw 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 degraded by a loss of all high pressure make up systems. These events are slw developing, w il understood transients which i
allw the operator sufficient time (at least 30 to 40 minutes on a worst case basis) to take the appropriate actions. Thus, we consider the current design to be adequate.
However, in response to NUREG-0737, Itm II.K.3.18 we have cmmitted to more fully autmate the depressurization function l
such that manual depressurization will no longer be required for i
these events. This will be accomplished by adding a bypass timer l
to the ADS logic such that the high drywell pressura initiation signal will no longer be required in the presence of a sustained reactor lw 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 depressurization is not warranted. Specific instructions will be included in the trip procedures on the use of this feature.
In recognition of the Staff's view of the importance of this item, we have agreed to inplement these changes on an accelerated schedule such that these modifications will be in place prior to fuel load.
2.
HPCI/RCIC Rom Cooling In the analysis of the loss of offsite power initiator in the Limerick PM, the various dependencies of the HPCI and RCIC systems were considered. One of the dminant contributors to the unavailability of these systems for a loss of offsite power event is the failure of the diesel generators to supply power. For this lw probability event, the HPCI and BCIC systems would continue to operate off their DC power supplies, however, rom cooling for the HPCI and RCIC cmpartments would be lost.
In recognition of the dependencies of these systems on the cooling function, preliminary calculations were performed to demonstrate that natural circulation cooling could be established by opening the cmpartment doors such that the time available to repair the diesels or restore offsite power is significantly increased. 'Ihe analysis demonstrated the effectiveness of this alternate moling nethod without the need for forced circulation.
We are currently in the process of developing the necessary procedures to mitigate this type of event and as part of this effort will review the original calculations to verify that the conclusions are still valid and that forced circulation is not required.
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3.
Containment Sprays The inportance of this function of the residual heat Imoval systan has been recognized by the industry in the developnent of the Dnergency Pro dure Guidelines. The Limerick T.R.I.P.
Procedures make extensive use of the containment sprays within-the containment Control Guidelines to limit pressure in both the drywell and the wetwell. Given the extensive operator training in these procedures, proper operation of the system to delay or prevent contaiment failure is assured.
The availability of the containment sprays is assured by demonstrating its operability through periodic testing. Many of the conponents required to function in the containment spray mode of tne Mm system are also required'.to function in its shutdown cooling, suppression pool cooling and low pressure injection modes. A review of the surveillance testing requirements for the Mm systs indicates that operability of the containment spray mode is demonstrated 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.
Sincerely, Skj Copy to: See attached service list' r
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.e cca Judge Lawrence Brenner Judge Peter A. Morris Judge Richard F. Cole-Troy B. Conner, Jr., Esq.
Ann P. Ilodgdon, Esq.
Mr. Frank R. Ikrnano Mr. Robert L.-Anthony it. Marvin I. Lewis Charles W. Elliot, Esq.
Zori G. Ferkin, Esq.
Mr. Thanas Gerusky Director, Penna. Emergency Management Agency Mr. Steven P. !!crshey Angus Iove, Esq.
Mr. Joseph II. White, III David Wersen, Erq.
Robert J. Sugaman, Esq.
Spence W. Perry, Esq.
Jay M. Gutierrez, Esq.
Atcmic Safety & Licensing Appeal Board Atonic Safety & Licensing Board Panel Docket & Service Section Martha W. Bush, Esq.
James Wiggins Mr. Tinothy R. S. Canpbell Phyllis Zitzer e