ML13247A742

Prairie Island Nuclear Generating Plant, Unit 2 - Review of the 2012 Steam Generator Tube Inspection Report for Refueling Outage 27

ML13247A742
Person / Time
Site:	Prairie Island
Issue date:	09/18/2013
From:	Wengert T J Plant Licensing Branch III
To:	Lynch J E Northern States Power Co
Wengert T J
References
TAC MF0080
Download: ML13247A742 (4)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 September 18, 2013 James E. Lynch Site Vice President Prairie Island Nuclear Generating Plant Northern States Power Company -Minnesota 1717 Wakonade Drive East Welch, MN 55089-9642 PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT 2 -REVIEW OF THE 2012 STEAM GENERATORTUBE INSPECTION REPORT FOR REFUELING OUTAGE 27 (TAC NO. MF0080)

Dear Mr. Lynch:

By letter dated November 16, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 12326A857),

Northern States Power Company (the licensee) submitted information summarizing the results of the 2012 steam generator (SG) tube inspections at Prairie Island Nuclear Generating Plant (PINGP),

Unit 2. In addition to this report, the U.S. Nuclear Regulatory Commission (NRC) staff summarized a conference call concerning the 2012 SG tube inspections at PINGP, Unit 2, in a letter dated May 14, 2012 (ADAMS Accession No. IVIL 12128A415).

The NRC staff has completed its review and concludes that the licensee provided the information required by their technical specifications.

No additional follow up is required at this time. The staff's review of this report is enclosed.

If you have any questions regarding this matter, please contact me at (301) 415-4037.

Sincerely, Thomas J. Wengert, Senior Project Manager Plant Licensing Branch 111-1 . Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-306

Enclosure:

Review of 2012 Steam Generator Tube I nspection Report cc w/encl: Distribution via ListServ UNITED STATES NUCLEAR REGULATORY COMMISSION REVIEW OF 2012 STEAM GENERATOR TUBE INSPECTION REPORT FOR REFUELING OUTAGE 27 PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT 2 DOCKET NO. 50-306 By letter dated November 16, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 12326A857),

Northern States Power Company (the licensee) submitted information summarizing the results of the 2012 steam generator (SG) tube inspections at Prairie Island Nuclear Generating Plant (PINGP),

Unit 2. In addition to this report, the U.S. Nuclear Regulatory Commission (NRC) staff summarized a conference call concerning the 2012 SG tube inspections at PI NGP, Unit 2, in a letter dated May 14, 2012 (ADAMS Accession No. ML 12128A415).

PINGP, Unit 2, has two Westinghouse Model 51 SGs .. Each SG contains 3388 mill-annealed Alloy 600 tubes. Each tube has a nominal outside diameter of 0.875 inches and a nominal wall thickness of 0.050 inches. The tubes were roll-expanded into the tubesheet at both ends for approximately 2.75 inches, i.e., they are expanded for only a fraction of the tubesheet thickness and are considered partial depth hard-rolled tubes. The tubes are supported by a number of . carbon steel tube support plates. The original anti-vibration bars were removed and replaced.

The row one and two tubes were subjected to an in-situ thermal stress relief in May 2000. Many tubes have been roll-expanded into the tubesheet above the original factory roll expansion to permit flaws below these re-rolled locations to remain in service.

In addition to the depth-based tube repair criteria, the licensee is also authorized to apply the voltage-based tube repair criteria for predominantly axially-oriented outside diameter stress corrosion cracking (OOSCC) at the tube support plate elevations.

Although authorized to implement the voltage-based repair criteria, the licensee has not found it necessary to implement these criteria since few, if any, indications subject to this repair criteria have been identified at Unit 2. In addition, the licensee is authorized to leave flaws within the tubesheet region in service, provided they satisfy the F*/EF* repair criterion. The major cause of degradation within the tubesheet region is primary water stress corrosion cracking at the roll transition zones. Secondary side intergranular attack and OOSCC have also been observed at this location.

The licensee provided the scope, extent, methods, and results of their SG tube inspections in the documents referenced above. In addition, the licensee described corrective

actions, such as tube plugging, taken in response to the inspection findings.

The 2012 inspections were the last scheduled inspections for these SGs, which are scheduled to be replaced in the faU of 2013. Enclosure

-2 Based on a review of the information

provided, the NRC staff concludes that the licensee provided the information required by the technical specifications.

In addition, the staff concludes that there are no technical issues that warrant follow-up action at this time, since the inspections appear to be consistent with the objective of detecting potential tube degradation and that inspection results appear to be consistent with industry operating experience at similarly designed and operated units.

James E. Lynch September 18, 2013 Site Vice President Prairie Island Nuclear Generating Plant Northern States Power Company -Minnesota 1717 Wakonade Drive East Welch. MN 55089-9642 PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT 2 -REVIEW OF THE 2012 STEAM GENERATOR TUBE INSPECTION REPORT FOR REFUELING OUTAGE 27 (TAC NO. MF0080)

Dear Mr. Lynch:

By letter dated November

16. 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12326A857).

Northern States Power Company (the licensee) submitted information summarizing the results of the 2012'steam generator (SG) tube inspections at Prairie Island Nuclear Generating Plant (PINGP) Unit 2. In addition to this report, the U.S. Nuclear Regulatory Commission (NRC) staff summarized a conference call co'ncerning the 2012 SG tube inspections at PINGP, Unit 2. in a letter dated May 14, 2012 (ADAMS Accession No. ML12128A415).

The NRC staff has completed its review and concludes that the licensee provided the information required by their technical specifications.

No additional follow up is required at this time. The staff's review of this report is enclosed.

If you have any questions regarding this matter, please contact me at (301) 415-4037.

Sincerely, IRA! Thomas J. Wengert.

Senior Project Manager Plant licensing Branch 111-1 Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket No.

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