ML20117G653

Discusses 960514 Conference Call Re Feedwater Sys Pipe Breaks

ML20117G653
Person / Time
Site:	Mcguire, Catawba, McGuire
Issue date:	05/16/1996
From:	Tuckman M DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9605210526
Download: ML20117G653 (2)

Text

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11 1 DukeIbwerCompany M S Tlaaas U P.O. Box 1006 Senior VicePresident Charlotte, NC28201-1006 NuclearGeneration (704)382-2200 Otlice (704)3824360 Fax DUKEPOWDE May 16, 1996 U. S. Nuclear Regulatory Commission Attention: Document' Control Desk Washington, DC 20555

Subject:

Catawba Nuclear Station, Unit 1, Docket No. 50-413 McGuire Nuclear Station, Units 1 and 2, Docket'Nos. 50-369 and 370 On May 14, 1996, a' conference call was held between represent.atives of. Duke Power Company.and the NRC Staff.

The purpose ofLthe~ conference call was to clarify discussions of feedwater system pipe breaks that were.

provided in a-March 15, 1996 Response to an NRC Request for AdditionalInformation.

Consistent with the NRC-approved transient analysis methodology l(DPC-NE-3002), the feedwater system pipe break event is~ analyzed to' address two separate acceptance criteria: short-term core cooling (DNB) and long-term core cooling (hot leg boiling). Previous analyses have shown the feedline. break event to be non-limiting with respect to the primary and secondary system pressure limits; therefore, no explicit peak pressure calculations are performed for this event.

The results of the long-term core cooling evaluation, performed in support of the steam generator replacement, show that the pressurizer pressure reaches a peak of

.slightly.less than 2250 psig. This is significantly lower than the corresponding Model-D steam generator result. The primary reasons for this difference are the increased tube

. bundle heat transfer area and the elevated feedwater nozzle of the_feedring steam generator design. Both of these tend to enhance the overcooling phase of the feedline break transient and thereby reduce the RCS pressurization.

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'd U. S. Nuclear Regulatory Commission May 16, 1996 Page 2 Since the intent of the above analysis was to minimize the margin to hot leg boiling, assumptions were made for the initial and boundary conditions which minimize the RCS pressure. Were an explicit peak primary system pressure analysis to be performed, many of these assumptions would be reversed. The impact of the revised assumptions on the peak RCS pressure result has not been quantified. However, due to the large margin to the Standard Review Plan peak primary system pressure acceptance criterion of 3000 psig, this additional analysis was deemed to be unnecessary.

If additional information is required, please call Robert Sharpe at (704) 382-0956.

Very truly yours,

b.  %

M. S. Tuckman Attachments xc: S. D. Ebneter Regional Administrator, Region II U. S. Nuclear Regulatory Commission 101 Marietta Street, NW, Suite 2900 Atlanta, GA 30323 R. J. Freudenberger Senior Resident Inspector Catawba Nuclear Station G. F. Maxwell Senior Resident Inspector McGuire Nuclear Station P. S. Tam Project Manager, ONRR i V. Nerses

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