ML070390049

Inspection and Mitigation of Alloy 82/182 Pressurizer Butt Welds

ML070390049
Person / Time
Site:	Oconee
Issue date:	01/31/2007
From:	Brandi Hamilton Duke Energy Carolinas, Duke Energy Corp, Duke Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML070390049 (12)

Text

Duke Duke BRUCE Vice HHAMILTON President KciEnergy Oconee Nuclear Station Duke Energy Corporation ONOJ VP / 7800 Rochester Highway Seneca, SC 29672 864 885 3487 864 885 4208 fax bhhamilton@duke-energy.com January 31, 2007 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

Subject:

Duke Power Company LLC, d/b/a Duke Energy Carolinas, LLC Oconee Nuclear Station, Units 1, 2, and 3 Dockets Nos. 50-269, 270, and 287 Inspection and Mitigation of Alloy 82/182 Pressurizer Butt Welds In October of 2006, while performing inspections of its pressurizer Alloy 82/182 butt welds in accordance with MRP-139, "Primary System Piping Butt Weld Inspection and Evaluation Guideline," a pressurized water reactor licensee discovered several circumferential indications in its pressurizer surge, safety, and relief nozzles. Because of the potential importance of this issue, Duke is submitting this letter to notify the NRC regarding Oconee's actions taken or planned for inspecting or mitigating Alloy 600/82/182 butt welds on pressurizer spray, surge, and relief lines.

This letter contains four attachments. Attachment 1 is a description of the current Reactor Coolant System (RCS) leakage monitoring program for Oconee Units 1, 2, and 3. Attachment 2, 3, and 4 are compilations of the inspection and mitigation effort for pressurizer Alloy 600/82/182 butt welds for Oconee Units 1, 2, and 3. Details concerning the locations inspected and mitigated are provided in Attachments 2, 3, and 4. Future inspections of pressurizer butt welds at Oconee Units 1, 2, and 3 will be performed in accordance with ASME Code and MRP-139.

www. duke-energy. com

U. S. Nuclear Regulatory Commission Page 2 January 31, 2007 The NRC will be informed if Oconee revises any of the information contained in this letter.

Our staff is available to meet with the NRC to discuss any of the information contained in this letter. If there are any questions, please contact Reene' Gambrell at (864) 885-3364.

Very truly yours, B.H. Hamilton, Vice President Oconee Nuclear Site Reactor Coolant System Leakage Monitoring Program 2 Oconee Unit 1 Inspection and Mitigation Summary for Alloy 600/82/182 Pressurizer Butt Welds 3 Oconee Unit 2 Inspection and Mitigation Summary for Alloy 600/82/182 Pressurizer Butt Welds 4 Oconee Unit 3 Inspection and Mitigation Summary for Alloy 600/82/182 Pressurizer Butt Welds

U. S. Nuclear Regulatory Commission Page 3 January 31, 2007 cc: Mr. L. N. Olshan, Project Manager Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 0-14 H25 Washington, D.C. 20555 Dr. W. D. Travers, Regional Administrator U.S. Nuclear Regulatory Commission - Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. D. W. Rich Senior Resident Inspector Oconee Nuclear Station Mr. Henry Porter, Director Division of Radioactive Waste Management Bureau of Land and Waste Management Department of Health & Environmental Control 2600 Bull Street Columbia, S.C. 29201

U. S. Nuclear Regulatory Commission Page 4 January 31, 2007 bcc:

L. F. Vaughn R. L. Gill - NRI&A C. J. Thomas - MNS R. D. Hart - CNS S. D. Capps P. E. Mabry J. A. Patterson P. A. Wells D. W. Peltola R. C. Gamberg D. V. Deatherage S. L. Batson D. B. Coyle K. R. Redmond R. V. Gambrell B. G. Davenport BWOG Working Group ONS Document Management ELL NSRB NEI

U.S. Nuclear Regulatory Commission January 31, 2007 Attachment 1 Reactor Coolant System Leakage Monitoring Program

U. S. Nuclear Regulatory Commission January 31, 2007 A water inventory balance program monitors reactor coolant leakage with established limits for continued operation specified in the technical specifications. This program will measure any leakage from components and small diameter nozzles as unidentified system leakage, which has an established operational limit of less than 1.0 gallons per minute. More restrictive plant procedures require an assessment of potential leak sources whenever unidentified leakage exceeds 0.15 gallons per minute. If leakage exceeds the more restrictive limit and the leak source remains unidentified, plant management would assess what additional leak investigation activities are required, or if plant shutdown is necessary.

If leakage increases based on the mass balance, limited walk downs at power would be performed to identify the source of the leakage. Evidence of leakage is evaluated and resolved through the corrective action program and Fluid Leak Management Program.

U. S. Nuclear Regulatory Commission January 31, 2007 Attachment 2 Oconee Unit 1 Inspection and Mitigation Summary for Alloy 600/82/182 Pressurizer Butt Welds

U. S. Nuclear Regulatory Commission January 31, 2007 . Oconee Unit I Inspection and Mitigation Summary for Alloy 600/82/182 Pressurizer Butt Welds Mitigation3 MRP-139 Volumetric Inspection Completed or to be Requirement Met or to be Met Completed (Start Date) Comments Function / Susceptible Material Outage Start Date Outage Designation Designation Description Designation (MM/YYYY)

Spray Nozzle Nozzle to safe-end NA' NA' 1EOC 23 Bare Metal Visual 2 per NRC Bulletin 2004-01:

1-PZR-WP45 weld, safe-end, and 10/2006 lEOC 22, 4/2005.

Pipe weld safe-end to pipe weld 1-PSP-1 Surge Nozzle to safe-end NA' NA' 1EOC 23 Bare Metal Visual2 per NRC Bulletin 2004-01:

I-PZR-WP23 weld 10/2006 1EOC 22, 4/2005.

Safety Nozzle to flange weld NA' NA' 1EOC 23 Bare Metal Visual 2 per NRC Bulletin 2004-01:

1-PZR-WP91-2 10/2006 1EOC 22, 4/2005.

Safety Nozzle to flange weld NA' NA' 1EOC 23 Bare Metal Visual 2 per NRC Bulletin 2004-01:

I-PZR-WP91-3 10/2006 1EOC 22, 4/2005.

Relief Nozzle to flange weld NA' NA' 1EOC 23 Bare Metal Visual2 per NRC Bulletin 2004-01:

1-PZR-WP91-1 10/2006 1EOC 22, 4/2005.

Note 1. Welds did not receive a PDI qualified examination prior to mitigation.

Note 2. Bare Metal Visual inspections detected no evidence of cracking or borated water leakage.

Note 3. Mitigation by full structural weld overlay.

Commission U. S. Nuclear Regulatory January 31, 2007 Attachment 3 for Alloy Unit 2 Inspection and Mitigation Summary Oconee Butt Welds 600/82/182 Pressurizer

U. S. Nuclear Regulatory Commission January 31, 2007 : Oconee Unit 2 Inspection and Mitigation Summary for Alloy 600/82/182 Pressurizer Butt Welds Mitigation3 MRP-139 Volumetric Inspection Completed or to be Requirement Met or to be Met Completed (Start Date) Comments Function / Susceptible Material Outage Start Date Outage Designation Designation Description Designation (MMI/YYYY)

Spray Nozzle Nozzle to safe-end NA' NA' 2 EOC 22 Bare Metal Visual2 per NRC Bulletin 2004-01 2-PZR-WP45 weld, safe-end, and 4/2007 conducted 2EOC 21, 10/2005.

Pipe Weld safe-end to pipe weld 2-PSP- 1 Surge Nozzle to safe-end NA1 NA' 2 EOC 22 Bare Metal Visual 2 per NRC Bulletin 2004-01 2-PZR-WP23 weld 4/2007 conducted 2EOC 21, 10/2005.

Safety Nozzle to flange weld NA' NA' 2 EOC 22 Bare Metal Visual 2 per NRC Bulletin 2004-01 2-PZR-WP91-2 4/2007 conducted 2EOC 21, 10/2005.

Safety Nozzle to flange weld NA' NA' 2 EOC 22 Bare Metal Visual2 per NRC Bulletin 2004-01 2-PZR-WP91-3 4/2007 conducted 2EOC 21, 10/2005.

2 Relief Nozzle to flange weld NA' NA' 2 EOC 22 Bare Metal Visual per NRC Bulletin 2004-01 2-PZR-WP9 1-1 4/2007 conducted 2EOC 21, 10/2005.

Note 1. No PDI qualified inspections have been conducted in the previous two refueling outages for these locations.

Note 2. Bare Metal Visual inspections detected no evidence of cracking or borated water leakage.

Note 3. Mitigation by full structural weld overlay.

U. S. Nuclear Regulatory Commission January 31, 2007 Attachment 4 Oconee Unit 3 Inspection and Mitigation Summary for Alloy 600/82/182 Pressurizer Butt Welds

U. S. Nuclear Regulatory Commission January 31, 2007 : Oconee Unit 3 Inspection and Mitigation Summary for Alloy 600/82/182 Pressurizer Butt Welds Mitigation3 Nozzle MRP-139 Volumetric Inspection Completed or to be Requirement Met or to be Met Completed (Start Date) Comments Function / Susceptible Material Outage Start Date Outage Designation Designation Description Designation (MM/YYYY)

Spray Nozzle Nozzle to safe-end NA' NA' 3 EOC 23 Bare Metal Visual 2 per NRC Bulletin 2004-01:

3-PZR-WP45 weld, safe-end, and 10/2007 3EOC 21, 10/2004; Pipe Weld safe-end to pipe weld 3EOC 22, 4/2006.

3-PSP-1 Surge Nozzle to safe-end NA' NA' 3 EOC 23 Bare Metal Visual' per NRC Bulletin 2004-01:

3-PZR-WP23 weld 10/2007 3EOC 21, 10/2004; 3-PZR-WP23 __3EOC 22, 4/2006.

Safety Nozzle to flange weld NA' NA' 3 EOC 23 Bare Metal Visual 2 per NRC Bulletin 2004-01:

3-PZR-WP91-2 10/2007 3EOC 21, 10/2004; 3EOC 22, 4/2006.

Safety Nozzle to flange weld NA' NA' 3 EOC 23 Bare Metal Visual' per NRC Bulletin 2004-01:

3-PZR-WP91-3 10/2007 3EOC 21, 10/2004; 3EOC 22, 4/2006.

Relief Nozzle to flange weld NA' NA' 3 EOC 23 Bare Metal Visual 2 per NRC Bulletin 2004-01:

3-PZR-WP9 1-1 10/2007 3EOC 21, 10/2004; 3EOC 22, 4/2006.

Note 1. These welds have not been inspected using PDI qualified techniques during the last two refueling outages.

Note 2. The Bare Metal Visual inspections detected no evidence of cracking or borated water leakage.

Note 3. Mitigation by full structural weld overlay.