ML070470272

Inspection and Mitigation of Alloy 82/182 Pressurizer Butt Welds

ML070470272
Person / Time
Site:	Catawba
Issue date:	02/08/2007
From:	Morris J Duke Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML070470272 (8)

Text

Duke JAMES R. MORRIS Vice President E Energy Catawba Nuclear Station 4800 Concord Rd. I CNO1 VP York, SC 29745-9635 803 831 4251 803 831 3221 fax February 8, 2007 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001

Subject:

Duke Power Company LLC d/b/a Duke Energy Carolinas, LLC (Duke)

Catawba Nuclear Station, Units 1 and 2 Docket Numbers 50-413 and 50-414 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 Catawba's actions taken or planned for inspecting or mitigating Alloy 600/82/182 butt welds on pressurizer spray, surge, safety, and relief lines.

This letter contains two attachments. Attachment 1 is a description of the current Reactor Coolant System (RCS) leakage monitoring program for Catawba Units 1 and 2. Attachment 2 is a compilation of the inspection and mitigation effort for pressurizer Alloy 600/82/182 butt welds for Catawba Units 1 and

2. Details concerning the locations inspected and mitigated are provided in Attachment 2. Future inspections of pressurizer butt welds at Catawba Units 1 and 2 will be performed in accordance with the ASME Code and applicable relief requests and MRP-139.

The NRC will be informed if Catawba revises any of the information contained in this letter.

www. duke-energy.com

U.S. Nuclear Regulatory Commission Page 2 February 8, 2007 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 L.J. Rudy at (803) 831-3084.

Very truly yours, James R. Morris LJR/s Attachments

U.S. Nuclear Regulatory Commission Page 3 February 8, 2007 xc (with attachments):

W.D. Travers, Regional Administrator U.S. Nuclear Regulatory Commission, Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, GA 30303 A.T. Sabisch, Senior Resident Inspector U.S. Nuclear Regulatory Commission Catawba Nuclear Station J.F. Stang, Jr., Senior Project Manager (addressee only)

U.S. Nuclear Regulatory Commission Mail Stop 0-8 H4A Washington, D.C. 20555-0001

Attachment 1 RCS Leakage Monitoring Information for Catawba Units 1 and 2

I 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 (unidentified leakage calculations are typically performed every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />). If leakage increases based on the mass balance, limited walkdowns at power would be performed to identify the source of the leakage. 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.

Evidence of leakage is evaluated and resolved through the Corrective Action Program and the Fluid Leak Management Program.

Attachment 1 Page 1

Attachment 2 Inspection and Mitigation Effort for Pressurizer Butt Welds for Catawba Units 1 and 2

Catawba Unit 1 Inspection and Mitigation Summary for Alloy 600/82/182 Pressurizer Butt Welds MRP-139 Volumetric Mitigation Nozzle Inspection Requirement Completed Met or to be Met Comments Function / Susceptible OeOutage Material Start Date Designation Description Designation Designation Spray Nozzle to safe-end NA' NA' lEOC 16 Bare Metal Visual 2 per NRC Bulletin 1PZR-W2SE weld 11/2006 2004-0 1: 1EOC 15, 5/2005.

Surge Nozzle to safe-end NA' NA' 1EOC 16 Bare Metal Visual2 per NRC Bulletin 1PZR-WlSE weld 11/2006 2004-01: lEOC 15, 5/2005.

Safety Nozzle to safe-end NA' NA' lEOC 16 Bare Metal Visual 2 per NRC Bulletin 1PZR-W4ASE weld 11/2006 2004-01: 1EOC 15, 5/2005.

Safety Nozzle to safe-end NA' NA' lEOC 16 Bare Metal Visual 2 per NRC Bulletin 1PZR-W4BSE weld 11/2006 2004-01: lEOC 15, 5/2005.

Safety Nozzle to safe-end NA' NA' lEOC 16 Bare Metal Visual 2 per NRC Bulletin lPZR-W4CSE weld 11/2006 2004-01: 1EOC 15, 5/2005.

Relief Nozzle to safe-end NA' NA1 lEOC 16 Bare Metal Visual' per NRC Bulletin lPZR-W3SE weld 11/2006 2004-01: 1EOC 15, 5/2005.

Note 1. Prior to 1EOCl6, welds were not inspectable using a PDI qualified technique.

Note 2. This information is provided for historical purposes. A full structural weld overlay was applied at this location during 1EOC 16 to mitigate the effects of PWSCC. (Reference Relief Request 06-GO-001, Revision 1, dated September 27, 2006.)

Attachment 2 Page 1

Catawba Unit 2 Inspection and Mitigation Summary for Alloy 600/82/182 Pressurizer Butt Welds MRP-139 Volumetric Mitigation Nozzle Inspection Requirement Completed or to Met or to be Met be Completed Comments Function / Susceptible Outage Outage Material Start Date Designation Description Designation Designation Spray Nozzle to safe-end NA' NA' 2EOC 15 Bare Metal Visual 2 per NRC Bulletin 2PZR-W2SE weld 9/2007 2004-01: 2EOC 13, 9/2004; 2EOC 14, 3/2006.

Surge Nozzle to safe-end NA' NA' 2EOC 15 Bare Metal Visual 2 per NRC Bulletin 2PZR-W1SE weld 9/2007 2004-01: 2EOC 13, 9/2004; 2EOC 14, 3/2006.

Safety Nozzle to safe-end NA' NA' 2EOC 15 Bare Metal Visual 2 per NRC Bulletin 2PZR-W3SE weld 9/2007 2004-01: 2EOC 13, 9/2004; 2EOC 14, 3/2006.

Safety Nozzle to safe-end NA' NA' 2EOC 15 Bare Metal Visual 2 per NRC Bulletin 2PZR-W4ASE weld 9/2007 2004-01: 2EOC 13, 9/2004; 2EOC 14, 3/2006.

Safety Nozzle to safe-end NA' NAT 2EOC 15 Bare Metal Visual2 per NRC Bulletin 2PZR-W4BSE weld 9/2007 2004-01: 2EOC 13, 9/2004; 2EOC 14, 3/2006.

Relief Nozzle to safe-end NA' NA' 2EOC 15 Bare Metal Visual 2 per NRC Bulletin 2PZR-W4CSE weld 9/2007 2004-01: 2EOC 13, 9/2004; 2EOC 14, 1_ _ 1 3/2006.

Note 1. Welds are not inspectable using PDI qualified methods.

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

Attachment 2 Page 2