ML20042A154

Final Significant Deficiency Rept SD-9 Re Main Feedline Rupture W/Failure of Blowdown Sys.Design Modified to Include Cavitating Venturies to Preclude Uncontrollable Auxiliary Feedwater Flows to Faulted Steam Generator

ML20042A154
Person / Time
Site:	Millstone
Issue date:	03/03/1982
From:	Counsil W, Werner R NORTHEAST NUCLEAR ENERGY CO.
To:	Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, AEC-MP3-269, B10447, NUDOCS 8203230148
Download: ML20042A154 (2)

Text

General OHices e Seiden Street, Berlin, Connecticut 3 .".ENNUSEI F CONNECTICUr 06101

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March 3, 1982 Docket No. 50-423 o 9 \

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L Mr. Ronald C. Haynes MAN 28 Jgg ]

f of Inspection and Enforcement U. S. Nuclear Regulatory Commission OJ hg 631 Park Avenue 4 King of Prussia, PA 19406 A 9

References:

(1) W. G. Counsil letter to B. H. Grier, Reporting of Deficiencies in Design and Construction, dated October 9, 1980.

Gentlemen:

Millstone Nuclear Power Station, Unit No. 3 Reporting of Potential Significant Deficiencies in Design and Construetion; Final Report SD-9 Main Feedline Rupture with Failure of Blowdown System As required by Title 10, Code of Federal Regulations Part 50, Paragraph 55(e), Northeast Nuclear Energy Company (NNECO) reported a potential significant deficiency in the design of Millstone Unit No. 3 in Reference (1). As described in Reference (1), NNECO was notified by Westinghouse i Electric Corporation, Water Reactor Division, that a main feedline l

rupture with an assumed failure in the steam generator blowdown system could lead to reduced cooling to the steam generator.

In response to the above potential design deficiency, the design of the affected systems was reviewed and a design change was initiated. Based upon the current system design we have reached the following conclusions:

1 The present Millstone Unit No. 3 design has been modified to include cavitating venturies to preclude uncontrollable auxiliary feedwater flows to a faulted steam generator in the event of steam generator blowdown isolation valve failure and concurrent main feedwater line rupture. The cavitating venturies are designed to ensure adequate flow is maintained to the intact steam generators while maintaining the maximum auxiliary feedwater flow so as to prevent pump runout and a subsequent pump trip.

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Based upon the above system review and corrective actions, we consider Millstone Unit No. 3 to be free of the reported potential significant deficiency.

This letter constitutes our final report closing out all items related to SD- 9. We trust the above information satisfactorily responds to your Concerns.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY 4 /L x s

' W. G. Counsilg Senior Vice'P' resident

// O by: f L h 4 , i- -

R. P. Werner Vice President Generation Engineering & Construction cc: Mr. E. J. Brunner, Chief Region 1 Division of Resident and Project Inspection Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission 631 Park Avenue l

King of Prussia, PA 19408 1

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