ML20129D312

Discusses 960627 Northern States Power Co Technical Justification to Revise Previous Commitment Made in to Perform mid-cycle Insp of Certain SG Tube Sleeve Welds.Staff Finds mid-cycle Outage Insp Not Warranted

ML20129D312
Person / Time
Site:	Prairie Island
Issue date:	09/25/1996
From:	Hannon J NRC (Affiliation Not Assigned)
To:	Richard Anderson NORTHERN STATES POWER CO.
References
TAC-M94486, NUDOCS 9609300036
Download: ML20129D312 (4)

Text

Mr. Roger.0.-Anderson; Director.

Lictnsing and Manag: ment' Issues.

September 25, 1996 Northern States Pcwer Company 414 Nicollet Mall-.

Minneapolis, MN 55401

SUBJECT:

PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT NO. 1, JUSTIFICATION l

FOR CANCELLATION OF MID-CYCLE OUTAGE INSPECTION (TAC NO. M94486)

Dear Mr. Anderson':

By [[letter::05000282/LER-1996-011, :on 960528,discovered Degraded Steam Generator Sleeves.Caused by Inadequate Cleaning of Parent Tube Prior to Insertion of Sleeves.Implemented Improved Cleaning & Addl Nondestructive Exam Re Installation of Sleeves|letter dated June 27, 1996]],' Northern States Power Co. provided technical justification to. revise a previous commitment, made in a letter dated February 28, 1996, to perform a mid-cycle inspection of certain steam generator tube sleeve welds in steam generator 12 of Prairie Island Unit No. 1.

The need for a mid-cycle inspection depended upon the outcome of metallurgical examination -(root-cause determination) of certain pulled tube samples containing nondestructive examination (NDE) indications that were discovered in a limited number of. sleeve-to-tube welds during the spring 1996 refueling outage.

Improved NDE technology allowed the detection of the small, l

previously undetectable, weld defects during the spring 1996 refueling outage.

The staff has reviewed your justification for withdrawing the commitment for a mid-cycle inspection outage.

The staff has found that the sleeve weld l

indications are not due to service-induced degradation.

Instead, they are original fabrication flaws that were the result of faulty tube surface cleaning prior to welding.

Based upon the root-cause determination, analyses, and tests, the staff finds that a mid-cycle outage to inspect the subject tube-to-sleeve welds is not warranted. Northern States Power may operate Prairie Island Nuclear Generating Plant, Unit No.1 throughout the entire operating cycle 18.

j This completes our review of TAC No. M94486. If you have any questions regarding our review of this issue, please contact Beth Wetzel at (301) 415-t 1355.

Sincerely, Original Signed By:

John N. Hannon, Director Project Directorate III-l Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation Docket No. 50-282 cc:

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DOCUMENT NAME: G:\\WPDOCS\\ PRAIRIE \\PI94486A.LTR *See previous concurrence 1.

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warranted. The licensee may operate Prairie Island Nuclear Ge rating Plant, Unit I throughout the entire operating Cycle 18.

The staff further notes that the licensee made a new comm ment for the refueling outage inspection currently scheduled for the all 1997. That commitment states:

"A 100% examination of all sleeves using cur nt state-of-the-art Appendix H qualified eddy current technique will be done. A reexamination of all sleeve welds with re lting volumetric and crack-like ET indications will be done by UT."

The acceptance criteria for this inspectio are under development and will be submitted for staff review when the revis d ABB-CE topical report for welded sleeves is submitted later this year.

As a future action, the licensee int ds to seek a license amendment to update the current ABB-CE Sleeving Topical eport to the latest revision when it becomes available later this year This completas our review of T No. M94486. If you have any auestions l

regarding our review of this sue, please contact Beth Wetzel at (301) 415-l 1355.

l l

Sincerely, l

John N. Hannon, Director Project Directorate 111-1 Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation j

cc:

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DISTRIBUT ON:

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'N' = No copy

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k*****,o September 25, 1996 Mr. Roger 0. Anderson, Director Licensing and Management Issues Northern States Power Company l

414 Nicollet Mall l

Minneapolis, MN 55401 l

SUBJECT:

PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT NO.1, JUSTIFICATION FOR CANCELLATION OF MID-CYCLE OUTAGE IllSPECTION (TAC N0. M94486)

Dear Mr. Anderson:

By [[letter::05000282/LER-1996-011, :on 960528,discovered Degraded Steam Generator Sleeves.Caused by Inadequate Cleaning of Parent Tube Prior to Insertion of Sleeves.Implemented Improved Cleaning & Addl Nondestructive Exam Re Installation of Sleeves|letter dated June 27, 1996]], Northern States Power Co. provided technical justification to revise a previous commitment, made in a letter dated February 28, 1996, to perform a mid-cycle inspection of certain steam generator tube sleeve welds in steam generator 12 of Prairie Island Unit No. 1.

The need for a mid-cycle inspection depended upon the outcome of metallurgical examination (root-cause determination) of certain pulled tube l

samples containing nondestructive examination (NDE) indications that were discovered in a limited number of sleeve-to-tube welds during the spring 1996 refueling outage.

Improved NDE technology allowed the detection of the small, previously undetectable, weld defects during the spring 1996 refueling outage.

The staff has reviewed your justification for withdrawing the commitment for a j

mid-cycle inspection outage. The staff has found that the sleeve weld 1

indications are not due to service-induced degradation.

Instead, they are original fabrication flaws that were the result of faulty tube surface cleaning prior to welding.

Based upon the root-cause determination, analyses, and tests, the staff finds that a mid-cycle outage to inspect the subject tube-to-sleeve welds is not warranted. Northern States Power may operate Prairie Island Nuclear Generating Plant, Unit No. I throughout the entire operating cycle 18.

This completes our review of TAC No. M94486. If you have any questions regarding our review of this issue, please contact Beth Wetzel at (301) 415-j 1355.

l Sincerely,

\\

/

W John N. Hannon, Director h

/ Project Directorate 111-1 i

/

Division of Reactor Projects - 'II/IV Office of Nuclear Reactor Regulation Docket No. 50-282 cc:

See next page

i-Prairie Island Nuclear Generating Mr. Roger 0. Anderson, Director Plant Northern States Power Company cc:

J. E. Silberg, Esquire Shaw, Pittman, Potts and Trowbridge j

2300 N Street, N. W.

)

Washington DC 20037 Site General Manager Prairie Island Nuclear Generating Plant Northern States Power Company 1717 Wakonade Drive East Welch, Minnesota 55089 1

Adonis A. Nebiett Assistant Attorney General l

Office of the Attorney General 455 Minnesota Street Suite 900 St. Paul, Minnesota 55101-2127 U.S. Nuclear Regulatory Commission Resident Inspector's Office 1719 Wakonade Drive East Welch, Minnesota 55089-9642 i

Regional Administrator, Region III U.S. Nuclear Regulatory Commission 801 Warrenville Road l

Lisle, Illinois 60532-4351 Mr. Jeff Cole, Auditor / Treasurer l

Goodhue County Courthouse I

Box 408 Red Wing, Minnesota 55066-0408 Kris Sanda, Commissioner Department of Public Service 121 Seventh Place East l

Suite 200 i

St. Paul, Minnesota 55101-2145 I

Site Licensing i

Prairie Island Nuclear Generating Plant Northern States Power Company 1717 Wakonade Drive East Welch, Minnesota 55089 March 1993 i

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