ML20043E883

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Requests NRC Authorization to Use Plugs Fabricated of nickel-chromium-iron Uns N-06690 Matl Alloy 690 to Plug Tubes in Steam Generators of Plant
ML20043E883
Person / Time
Site: Millstone Dominion icon.png
Issue date: 06/05/1990
From: Mroczka E
NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
B13543, NUDOCS 9006130488
Download: ML20043E883 (2)


Text

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d ' to ' h e:

  • General Offices
  • Seiden street Berlin. Connecticut 9 .'" Y S U '5[ 7" D Y P.O. BOX 270 HARTFORD. CONNECTICUT 06141 o27o I L ' 2 7.,l,.Z,'[,,7,*77,,,,,

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June 5, 1990

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Docket No. 50-336 B13543 j Re: 10CFR50.55a U.S. Nuclear Regulatory Commission '

Attention: Document Control Desk Washington, DC 20555 1

Gentlemen: i Millstone Nuclear Power Station, Unit No. 2 Steam Generator Tube Reoair In accordance with. 10CFR50.55a(a)(3), Northeast Nuclear Energy Company )

(NNECO), on behalf of Millstone Unit No. 2, hereby requests to use plugs  ;

fabricated of nickel chromium-iron UNS N 06690 material (Alloy 690) to plug -

tubes in the steam generators of Millstone Unit No. 2. l This material is; the subject of Code Case N-474-1 of the ASME Boiler and Pressure Vessel Code which has been approved by the Code Committee and which has been ' recently published. The subject code case authorizes the use of nickel-chromium-iron UNS N-06690 material (Alloy 690) in additional forms in the construction of Section III, Division 1, Class 1 components. Unfor- ,

tunately, the product Form SB166 (Bar) was unintentionally omitted in the ,

. final printing of the code case. Discussions with Christian Sanna, Secretary, <

ASME Section III, identified that this omission will be corrected, by errata, in a future: supplement. The material is specified in ASME Code, Section 11 Material Specifications SB-163, SB-166, SB 167, and SB-168. Previously,  :

Alloy 690 in tubing form (SB-163) has been authorized for construction of Class I components. ' The subject code :.ase, including SB166 product form, was  :

approved November 30, 1989.

-The change to the use of Alloy 690 for tube plugs has been made as a result of material corrosion considerations. The NRC Staff endorsed the use of ,

Alloy 690 for fabrication of mechanical plugs for steam generator tubes in NRC Bulletin No. 89-01, " Failure of Westinghouse Steam Generator Tube Mechanical ,

Plugs,".May 15,.1989. Additionally, this material is used in the fabrication  ;

of plugs which may be welded into steam generator tubes in Millstone Unit No. 2. Alloy 690 has similar mechanical properties to the Alloy 600 material previously used for tube plugs. The Design Stress Intensity stipulated by the code case and used in the design and qualification of the tube plugs is the r same as for Alloy 600 material of the same form. i Submittal of. this letter was preceded by a telephone conversation with Mr. H. F. Conrad, NRC, on June 1,1990, in which verbal concurrence was given to use this material for our specific application. .

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. j U.S. Nuclear Regulatory Commission I B13543/Page 2 June 5, 1990 NNECO respectfully requests that the NRC respond with formal concurrence for the use of this material prior to Millstone Unit No. 2 start-up presently scheduled for June 10, 1990. '

Very truly yours,  !

NORTHEAST NUCl. EAR ENERGY COMPANY j My W E. J.'trgczka /  !

Senior Vice President 1

cc: T. T. Martin, Region I Administrator i G. S. Vissing, NRC Project Manager, Millstone Unit No. 2 W. J. Raymond, Senior Resident inspector, Millstone Unit Nos. 1, 2, and 3 H. F. Conrad, NRR, Engineering Materials and Chemistry Branch s

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