ML071410300

North Anna, Unit 2 - Submittal of Stress Evaluation, Preliminary Engineering Evaluation of Insurge/Outsurge Tranients and Examination Results for the Completed Alloy 600 Pressurizer Nozzle Alternative Weld Repair CMP-023R1

ML071410300
Person / Time
Site:	North Anna
Issue date:	05/16/2007
From:	Bischof G T Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, NRC/NRR/ADRO
References
06-1007B, CMP-023R1
Download: ML071410300 (3)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RicHMOND, VIRGINIA 23261 May 16, 2007 U.S. Nuclear Regulatory Commission Serial No. 06-1007B Attention:

Document Control Desk NLOS /ETS One White Flint North Docket No. 50-339 11555 Rockville Pike License No. NPF-7 Rockville, MD 20852-2738 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNIT 2 SUBMITTAL OF STRESS EVALUATION, PRELIMINARY ENGINEERING EVALUATION OF INSURGE/OUTSURGE TRANSIENTS AND EXAMINATION RESULTS FOR THE COMPLETED ALLOY 600 PRESSURIZER NOZZLE ALTERNATIVE WELD REPAIR CMP-023R1 In a letter, dated January 3, 2007 (Serial No. 06-1007), as supplemented on March 13, 2007 (Serial No. 06-1007A), Dominion requested approval to use a proposed alternative to apply dissimilar metal weld overlays for repair/replacement activities associated with Alloy 600 materials.

That request contained alternative requirements for the North Anna Units 1 and 2 Inservice Inspection (ISI) programs to perform full structural preemptive weld overlays (PWOLs) to mitigate the potential for primary water stress corrosion cracking (PWSCC) susceptibility for those pressurizer nozzles containing Alloy 600.As stated in our Relief Request, Dominion committed to provide: (1) the final stress analysis for five of the weld overlays and the preliminary engineering evaluation of insurge/outsurge transients for the surge line prior to entry into Mode 4; (2) the examination results of the weld overlays; and, (3) a discussion of any repairs to the overlay material and/or base material and the reason for the repair; within 14 days after the completion of the ultrasonic examination of weld overlay installations.

The examination results of the six completed PWOLs and the proprietary version of the stress analysis for the mitigated nozzles and the preliminary engineering evaluation of insurge/outsurge transients were submitted directly to Mr. S. P. Lingam of your staff on April 11, 2007. This letter documents the submittal of the above information and provides:

1) the non-proprietary version of the stress analysis and the insurge/outsurge evaluation for public disclosure (Attachment 1); 2) a proprietary version of revision 2 to calculation 32-9035736-002 (Attachment 2); 3) the required affidavit to support the classification of the information previously submitted to Mr. S. P. Ungam, as well as, the revised calculation in Attachment 2 (Attachment 3); and, 4) the following restatement of the examination results of the mitigated pressurizer nozzles.AFto~

Serial No. 06-1007B Docket No. 50-339 Alternative Request CMP-023R1 Page 2 of 3 Six full structural mitigative PWOLs for the North Anna Unit 2 pressurizer safety, spray, relief, and surge nozzles were performed during the spring 2007 refueling outage (N2R18) in accordance with relief request CMP-023R1.

The surface and volumetric examinations of the weld and base material were completed with no recordable indications.

The examinations resulted in 100% coverage in accordance with relief request CMP-023R1 for both the preservice and inservice examination volumes. There were no repairs necessary to the weld overlay material or base metal during the installation of the PWOLs.This letter also satisfies the 60-day notification commitments made in Dominion letter dated February 26, 2007 (Serial No. 07-0035B) and the NRC Confirmatory Action Letter dated March 29, 2007 for North Anna Unit 2.If you have any questions regarding this submittal, please contact Mr. Thomas Shaub at (804) 273-2763.Very truly yours, Gerald T. Bischof Vice President

-Nuclear Engineering Attachments

1. Non-proprietary

-PWOL Stress Analysis Calculations For Alloy 600 Pressurizer Nozzle Repair.2. Proprietary

-PWOL Stress Analysis Calculation 32-9035736-002.

3. Affidavit

-PWOL Stress Analysis Results For Alloy 600 Pressurizer Nozzle Repair.Commitments made in this letter: None Serial No. 06-1007B Docket No. 50-339 Alternative Request CMP-023R1 Page 3 of 3 cc: U.S. Nuclear Regulatory Commission (without attachments)

Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 Mr. J. E. Reasor, Jr. (without attachments)

Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.Suite 300 Glen Allen, Virginia 23060 Mr. J. T. Reece (without attachments)

NRC Senior Resident Inspector North Anna Power Station Mr. S. P. Lingam NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8-H12 Rockville, Maryland 20852 Mr. M. M. Grace (without attachments)

Authorized Nuclear Insurance Inspector North Anna Power Station