ML070570535

Revised Actions for the Inspection and Mitigation of Alloy 82/182 Pressurizer Butt Welds

ML070570535
Person / Time
Site:	North Anna
Issue date:	02/26/2007
From:	Christian D Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
07-0035B
Download: ML070570535 (4)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 February 26, 2007 U.S. Nuclear Regulatory Commission Serial No.: 07-00358 ATTN: Document Control Desk NL&OSIETS: R1 Washington, DC 20555 Docket Nos. : 50-3381339 LicenseNos.: NPF-417 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNITS 1 AND 2 REVISED ACTIONS FOR THE INSPECTION AND MITIGATION OF ALLOY 821182 PRESSURIZER BUTT WELDS In a January 31, 2007 letter (Serial No. 07-0035), Dominion submitted plans for inspection and mitigation of Alloy 821182 pressurizer butt welds at North Anna Power Station Units 1 and 2. The letter also included compensatory actions until the welds were mitigated. In a February 16, 2007 phone call with North Anna plant management, the NRC discussed Dominion's commitments and compensatory actions. The NRC staff requested Dominion implement specific RCS leakage action levels and actions until mitigation is complete. This letter provides the information requested by NRC, as well as, summarizes Dominion's commitments associated with the inspection and mitigation of Alloy 821182 pressurizer butt welds. The actions and commitments in this letter supercede the actions and commitments identified in Dominion's January 31, 2007 letter.

Butt Weld Mitiaation Dominion will complete mitigation activities on the Alloy 821182 pressurizer butt welds during the spring 2007 refueling outage for North Anna Unit 2 and the fall 2007 refueling outage for North Anna Unit 1.

Leakaae Monitorinq Dominion will perform daily measurement of unidentified leakage in Modes 1, 2, and 3 for Units 1 and 2 until mitigation of the affected pressurizer butt welds has been completed on the respective units. The following RCS unidentified leakage rate action levels have been implemented:

0.25 gpm unidentified leakage rate above a baseline sustained for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> with at least 0.25 gpm of the change not confirmed from sources other than the pressurizer nozzle welds.

Serial No. 07-0035B Docket Nos. 50-3381339 Page 2 of 3 The value assigned as the baseline RCS leakage rate will be established using RCS leak rate information collected during the first seven (7) days of full power operation following the most recent bare metal visual examination of the Alloy 821182 pressurizer butt welds.

0.1 gpm unidentified leakage rate change from one day to the next sustained for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> with at least 0.1 gpm of the change not confirmed from sources other than the pressurizer nozzle welds.

The daily leakage rate measurement will be compared to the previous 3 days average to establish the magnitude of the change.

Leakage rate measurements will be obtained only during steady state operation.

Measurements obtained during plant transient conditions will not be used.

Reauired Actions Dominion will take the following actions based on RCS leak rate monitoring. If the RCS leakage remains above the baseline or daily action levels for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and the leakage is not confirmed to be from sources other than the pressurizer nozzle welds, the Unit will be placed in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 5 within an additional 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> and a bare metal visual inspection will be performed on unmitigated pressurizer surge, spray, safety and relief nozzle butt welds and safe end butt welds containing Alloy 821182 material.

If either North Anna Unit 1 or 2 is shutdown due to increased unidentified leakage, Dominion will report any subsequent bare metal visual inspection results of the pressurizer nozzle butt welds and safe end butt welds containing Alloy 821182 material within 60 days of unit restart. Further, Dominion will report within 60 days of a unit restart any 1) inspection results or 2) corrective or mitigative actions taken on pressurizer nozzle and safe end butt welds scheduled for mitigation in 2007.

Dominion will notify the NRC in writing prior to any changes made to the above commitments. These commitments will remain in effect until pressurizer surge, spray, safety and relief nozzle butt welds and safe end butt welds containing Alloy 821182 material are mitigated.

Serial No. 07-00358 Docket Nos. 50-3381339 Page 3 of 3 If you have any questions or require additional information, please contact Mr. Thomas Shaub at (804) 273-2763.

Very truly yours, David A. Christian Senior Vice President - Nuclear Operations and Chief Nuclear Officer

Attachment:

Commitment Summary cc: U. S. Nuclear Regulatory Commission Region II Regional Administrator Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 231-85 Atlanta, Georgia 30303 Mr. S. P. Lingam NRC Project Manager North Anna and Surry U. S. Nuclear Regulatory Commission One White Flint North 1 1555 Rockville Pike Rockville, MD 20852-2738 Mr. R. E. Martin NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 Mr. J. T. Reece NRC Senior Resident Inspector North Anna Power Station

Serial No. 07-00358 Docket Nos. 50-3381339 Attachment COMMITMENT

SUMMARY

INSPECTION AND MITIGATION OF ALLOY 821182 PRESSURIZER BUTT WELDS Scheduled Commitment Completion Date (If Required)

Dominion will complete the mitigation activities of Alloy 8211 82 pressurizer butt welds during the N2-R-18 spring 2007 refueling outage for NAPS 2. Spring 2007 Dominion will complete the mitigation activities of Alloy 8211 82 pressurizer butt welds during the fall N1-R-I 9 2007 refueling outage for NAPS 1. Fall 2007 Dominion will implement the unidentified RCS leakage action limits and required actions as described in this letter. The limits and actions will remain in effect unit the pressurizer nozzles containing Alloy 8211 82 are mitigated.

If North Anna Unit 1 or 2 is shutdown due to increased unidentified leakage, Dominion will report any subsequent bare metal visual inspection results of the pressurizer nozzle butt welds and safe end butt welds containing Alloy 8211 82 material within 60 days of unit restart. -

Dominion will report the results of corrective or mitigation actions of Alloy 821182 pressurizer butt weld locations at North Anna 1 and 2 to the NRC within 60 days of startup from the outage during which they were performed. --

Dominion will notify the NRC in writing prior to any changes made to the above commitments.

The continuing commitments will remain in effect until pressurizer surge, spray, safety and relief nozzle butt welds and safe end butt welds containing Alloy 821182 material are mitigated.