B17574, Forwards Rev 0 to EMF-2079 & Rev 0 to EMF-2145,both Providing Results of Evaluation of Large Break LOCA Event for Mnps,Unit 2.No New Regulatory Commitments Contained within Ltr

Forwards Rev 0 to EMF-2079 & Rev 0 to EMF-2145,both Providing Results of Evaluation of Large Break LOCA Event for Mnps,Unit 2.No New Regulatory Commitments Contained within Ltr

ML20198G698
Person / Time
Site:	Millstone
Issue date:	12/21/1998
From:	Bowling M NORTHEAST NUCLEAR ENERGY CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20198G702	List: B17574, Forwards Rev 0 to EMF-2079 & Rev 0 to EMF-2145,both Providing Results of Evaluation of Large Break LOCA Event for Mnps,Unit 2.No New Regulatory Commitments Contained within Ltr ML20198G704 ML20198G716
References
B17574, NUDOCS 9812290147
Download: ML20198G698 (3)

Text

. - . . _ - - - . - - . - . - . - - . - - - . - - - - - . .,

l .' ' R gn Fury RORoute W), Tunioni, CT 06385 Northeast l

d Nuclzar Energy un. tone Nuclear Power Station Northeast Nuclear Energy company i P.O. Box 128 Waterford, CT 06385-0128 (860) 447-1791 Fax (860) 444-4277 The Northeaet Utilities System a

i DEC 21 1998 Docket No. 50-336 B17574

U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Millstone Nuclear Power Station, Unit No. 2 Laroe Break Loss of Coolant Accident Evaluation r

The purpose of this letter is to provide the NRC Staff with the results of the evaluation of the Large Break LOCA (LBLOCA) event for Millstone Unit No. 2. In a letter dated July 21,1998 Northeast Nuclear Energy Company (NNECO)* committed to evaluate i the LBLOCA event for- Millstone Unit No. 2 using both the existing approved uncorrected code and the corrected developmental code and to submit the results to

the Nuclear Regulatory Commission (NRC). The results of the evaluation of the

LBLOCA event for Millstone Unit No. 2 using the approved uncorrected code is

. summarized in Siemens report EMF-2079 Revision 0 " Millstone Unit 2 Large Break

LOCA/ECCS Analysis with Rep!acement Steam Generators" dated September i998

) (Attachment 1). The results were confirmed to be conservative using the corrected 7 developmental code. A reduction in the maximum Linear Heat Generation Rafe (LHGR) from 15.1 kW/ft to 14.6 kW/ft was necessary to assure that the approvrtd uncorrected code results bounded the corrected developmental code results.

. Subsequent to completion of report EMF-2079 Revision 0, an issue was identified with l respect to the maximum containment spray flow rate. It was necessary to revise the t .LBLOCA analysis to reflect an increase in the maximum containment spray flow rate.

j ' Consistent with the Siemens commitment that LBLOCA analyses performed after i

i. August 31,1998 would use the new revised model, the revised LBLOCA analysis with

. the higher containment spray flow rate was performed with the LBLOCA model as EMF-2087 "SEM/PWR: ECCS Evaluation Model for PWR

.LBLOCA described in Siemens reyThe revised model corrects the excessive variability Applications."

. and modifies the Dougall-Rohsenow correlation. The results for the revised analysis p

1 m Letter from M.' L. Bowling to U. S. Nuclear Regulatory Commission, " Millstone Nuclear Power Station i Unit No. 2 Proposed Plan to Resolve issues Conceming the Large Break Loss of Coolant Accident Evaluation Model", dated July 21,1998.

A Letter from J. F. Mallay to U. S. Nuclear Regulatory Commission, " Request for Review of EMF-2087(P) SEM/PWR 98

ECCS Evaluation Model for PWR LBLOCA Application", dated August 31, f 1' 1998.

9812290147 981221 " 1

-eDR ADOCK 05000336,

e eDR c h1. h  ;

l

U.S. Nucl:ar Regul: tory Commission B17574\Page 2 with the new LBLOCA model is summarized in Siemens report EMF-2145 Revision 0

" Millstone Unit 2 Large Break LOCNECCS Analysis with . Replacement Steam Generators and Plant Modifications", dated November 1998 (Attachment 2). With the revised model acceptable results were demonstrated with a LHGR of 15.1 kW/ft.

There are no regulatory commitments contained within this letter.

N you have any additional questions concerning this submittal, please contact Mr. Ravi G. Joshi at (860) 440-2080.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY Martin L. Bowling \/

Recovery Officer - Technical Servi:es cc: H. J. Miller, Region 1 Administrator E. V. Imbro, Director, Millstone ICAVP inspections W. M. Dean, Director, Millstone Project Directorate W. D. Lanning, Director, Millstone Inspections J. P. Durr, Chief, inspections Branch S. Dembeck, NRC Project Manager, Millstone Unit No. 2 D. P. Beaulieu, Senior Resident inspector, Millstone Unit No. 2 l

Docket No. 50-336 B17574 l

l I

Attachment 1 Millstone Nuclear Power Station, Unit No. 2  ;

Large Break Loss of Coolant Accident Evaluation Siemens Report EMF-2079 Revision 0  :

Millstone Unit 2 Large Break LOCNECCS Analysis With Replacement Steam Generators ,

i l

December 1998