ML20207G163

Provides Addl Info to Support Util 861117 Application for Amend to License NPF-39 Re Operation W/Partial Feedwater Heating & Increased Core Flow.Info Re Peak Clad Temp Changes Submitted,Per Martin & Mccoy 861218 Request

ML20207G163
Person / Time
Site:	Limerick
Issue date:	01/02/1987
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Butler W Office of Nuclear Reactor Regulation
References
CON-#187-2116 OL, NUDOCS 8701060363
Download: ML20207G163 (2)

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PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.Op. BOX 8699 PHILADELPHI A. PA.191o1 mm e4n4ooo January 2, 1987 Docket No. 50-352 Mr. W. R. Butler, Director Project Directorate No. 4 Division of Boiling Water Reactor Licensing U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Dear Mr. Butler:

The purpose of this letter is to provide additional information for Philadelphia Electric Company's (PECo) November 17, 1986 Application for Amendment of Facility Operating License NPF-39, which requests changes to the Limerick Operating License and Technical Specifications relating to operation with partial feedwater heating and increased core flow.

The additional information pertaining to the peak clad temperature (PCT) changes was requested by Messrs. Martin and McCoy of the NRC staff during a telephone conversation with Mr.

Charles Mengers, PECo Licensing, on December 18, 1986. The question is restated, followed by our response.

Question:

NEDC-31323, Increased Core Flow and Partial Feedwater Heating Analyses for Limerick Generating Station Unit 1 Cycle 1, dated October 1986, page 2-4, states, " Results of the LOCA analysis performed for Limerick show that the PCT for ICF increases by less than 10 degrees F for the limiting break compared to the rated core flow condition. PCT changes throughout the remainder of the break spectrum will be of a similar magnitude and thus will not alter the limiting break size or failure." What is the basis for the statement " PCT changes throughout the remainder of the break spectrum will be of a similar magnitude and this will not alter the limiting break size or failure."?

- Response For large breaks (> 1.0 square foot) in the recirculation line, the calculated peak cladding temperature (FCT) response is governed by a combination of the initial blowdown heat g 8701060363 870102 f' NU

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PDR ADOCK 05000352 p PDR

Mr. W. R. Butler January 2, 1987

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transfer and the duration of core uncovery. For small breaks, nucleate boiling is assumed until core uncovery occurs so the FCT response is controlled by the duration of core uncovery.

The primary effect of increased core flow (ICF) on LOCA analysis is to alter the flow coastdown response following the assumed trip of the recirculation pumps at the time of the break. The flow coastdown is important only during the

early blowdown period. Changes to the duration of core l' uncovery are small since this depends on total vessel inventory and ECCS makeup capability which have not been altered for ICF.

1 Sensitivity studies have been performed for a large number of

, plants with ICF and consistently show a change in calculated i high power node dryout time of up to 0.2 seconds and a change in the duration of core uncovery of about 1 second. These small changes result in a PCT increase of less than 10 i degrees F.

4 The impact of ICF on the early blowdown only applies to large

} recirculation line breaks. It will be of similar magnitude j for all large breaks since high power node dryout occurs

after most of the pump coast down has been completed.

Changes in the duration of core uncovery will be similar

, across the entire break spectrum since they are insensitive

} to the initial core flow rate. Thus, the calculated PCT change across the break spectrum for ICF will be of a similar

! magnitude as was seen for the limiting break. In addition, j the limiting break will not change from the DBA' recirculation i suction break since it experiences both the most severe early blowdown and the longest period of core uncovery (Figure 6.3-1 74 of FSAR).

t If you have any questions or require additional j information, please do not hesitate to contact us.

Very truly yours,

[ //

I /

./ .'Cooney M 'ager i N clear Support Department I

i cc: E. M. Kelly, Senior Resident Site Inspector j See Attached Service List

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