ML20210Q003

Informs That Due to Printing Malfunction,Some Copies of Author Ltr Dtd 990726,may Not Have Included Second Page of Encl 2 of Ltr

ML20210Q003
Person / Time
Site:	Nine Mile Point
Issue date:	08/11/1999
From:	Hood D NRC (Affiliation Not Assigned)
To:	Judson T AFFILIATION NOT ASSIGNED
References
NUDOCS 9908130123
Download: ML20210Q003 (4)

Text

7 e-August 11, 1999 Mr. Tim Judson Syracuse Peace Council 924 Burnet Avenue Syracuse, NY 13203 -

SUBJECT:

OMITTED PAGE FOR PRIOR LETTER RE: NINE MILE POINT STATION, UNIT 1 CORE SHROUD

Dear Mr. Judson:

Due to a printing malfunction, some copies of my letter dated July 26,1999, to you may not have included the second page of Enclosure 2 of that letter, if your copy of Enclosure 2 does not consist of two pages, please add the enclosed page 2.

Sincerely Original signed by:

Darl S. Hood, Sr. Project Manager, Section 1 Project Directorate i Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-220

Enclosure:

As stated cc w/ encl: See next page DISTRIBUTION:

Docket Filt PUBLIC PDI-1 R/F f

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"C" - Copy without attachment / enclosure "E" - Copy with 1

' attachment / enclosure "N" = No copy

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August 11, 1999 Mr. Tim Judson Syracuse Peace Council 924 Burnet Avenue Syracuse, NY 13203

SUBJECT:

' OMITTED PAGE FOR PRIOR LETTER RE: NINE MILE POINT STATION, UNIT 1 CORE SHROUD

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Dear Mr. Judson:

Due to a printing malfunction, some copies of my letter dated July 26,1999, to you may not have included the second page of Enclosure 2 of that letter. If your copy of Enclosure 2 does not consist of two pages, please add the enclosed page 2.

Sincerely Original signed by:

Darl S. Hood, Sr. Project Manager, Section 1 Project Directorate i Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-220.

Enclosure:

As stated cc w/ encl: See next page DISTRIBUTION:

Docket File PUBLIC PDI-1 R/F DOCUMENT NAME: G:\\PDI-1\\NMP1\\CORESHRD.wpd To receive a copy of this document indicate in the box:

"C" - Copy without attachment / enclosure "E" - Copy with attachment / enclosure

• N" - No topy'-

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Aug'nt 11, 1999 Mr Tim Judson -

Syracuse Peace Council 924 Burnet Avec:ue Syracuse, NY 13203

)

SUBJECT:

OMITTED PAGE FOR PR!OR LETTER RE: NINE MILE POINT STATION, UNIT 1 CORE SHROUD o

Dear Mr. Judson:

Due to a printing malfunct on, some copies of my letter dated July 26,1999, to you may not have included the second page of Enclosure 2 9 that letter, if your copy of Enclosure 2 does not consist of two pages, please add the enclosed page 2.

Sincerely DadD n/

Darl S. Hood, Sr. Project Manager, Section 1 Project Directorate i Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No.50-22r

Enclosure:

As stated cc w/ encl: See next page

.i

Nine Mile Point Nuclear Station Unit No.1 negional Administrator, Region 1

Bernad M. Bordenick-U.S. Nuclear Regulatory Commission -

Attorney 3t Law 475 Allendale Road 9011 LeVe3e Drive King of Prussia, PA 19406 Chevy Chase MD 20815-5607 Resident inspector.

John H. Mueller

' U.S. Nuclear Regulatory Commission Chief Nuclear Officer P.O. Box 126 Niagara Mohawk Power Corporation Lycoming, NY 13093 Nine Mi!e Point Nuclear Station Operations Building, Secc,nd Floor Charles Donaldson, Esquire Lycoming, NY 13093 Assistant Attorney General New York Department of Law 120 Broadway New York, NY 10271 Mr. Paul D. Eddy State of New York Department of Public Service Power Division, System Operations 3 Empire State Plaza Albany, NY 12223 Mr. F. William Valentino, President New York State Energy, Research, and Development Authority Corporate Plaza West 286 Washington Avenue Extension Albany, NY 12203-6399 Mark J. Wetterhahn, Esquire Winston & Strawn 1400 L Street, NW Washington, DC 20005-3502 Gary D. Wilson, Esquire Niagara Mohawk Power Corporation 300 Erle Boulevard W'est Syracuse, NY 13202 Supervisor Town of Scriba Route 8, Box 382 Oswego, NY 13126

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. Niagara h Mohawk' Phone 315 34918U Richard B. Abbott 0***

Vice President Nuclear Engineenng July 12, 1999 NMPIL 1451 U. S. Nuclear Regulatory Commission

- Attn: Document Control Desk Washington, DC 20555 RE:

Nine Mile Point Unit 1 Docket No. 50-220 DPR-63

Subject:

Generic Letter 94-03,1ntergmnular Stress Cormsion Cmcking of Core Shrouds in Boiling Water Reactors, ' Final Root Cause Evaluation of a Cap Screw Failurefor a Stabilizer Assembly (Tie Rod)for Nine Mile Point Unit 1 Gentlemen:

By letter dated May 21,1999, Niagara Mohawk Power Corporation (NMPC) requested Staff approval of a proposed modification to each of the four tie rods pursuant to 10CFR50.55a(a)(3)(i). As stated in that letter, the modification replaces the design function of the failed cap screw and other cap screws that have the potential for future failure in the upper spring. NMPC also stated that the root cause evaluation was preliminary and that it would provide a final root cause evaluation within 30 days following restart of the unit. The purpose of this letter is to provide the final root cause evaluation.

The cause, as stated in our letter dated May 21,1999, was confirmed to be intergranular stress corrosion cracking in the alloy X-750 cap screw material due to large sustained stresses.

Specifically, these stresses were from differential thermal expansion of dissimilar materials fastened by the cap screw.

As also stated in that letter, a potential contributing cause was the sustained stresses that were attributed to the torquing of the cap screw associated with the original assembly of the tie rods.

NMPC has determined that the torquing process was properly controlled during initial assembly of the tie rods to provide reasonable assurance that the cap screws were not over torqued. Therefore, this potential contributing cause.has been eliminated.

Furthermore, as stated in the same letter, a second potential contributing cause was the stresses associated with friction between the reactor pressure vessel wall and the upper spring contact points. Based on a re-examination of the wear marks on the reactor pressure vessel wall and

. destructive testing of two cap screws from the 166 degree tic rod upper spring upper contact, NMPC has eliminated friction as a potential contributing cause.

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Page 2 The modification is unaffected by.these conclusions in that it was designed to address the combined effect of these three sources of stress on the subject caps crews. Accordingly.

NMPC continues to conclude that the proposed modification provides an acceptable level of quality and safety.-

4 Very truly yours, Richard B. Abbott Vice President - Nuclear Engineering

' RBA/KWK/ kap xc:

Mr. H. J. Miller, Regional Administrator, Region I

. Mr. S. S. Bajwa, Section Chief PD-1, Section 1, NRx Mr. G. K. Hunegs, NRC Senior Resident Inspector Mr. D. S. Hood, Senior Project Manager, NRR Records Management L