ML070330062

Inspection and Mitigation of Alloy 600/82/182 Pressurizer Butt Welds

ML070330062
Person / Time
Site:	Watts Bar, Sequoyah
Issue date:	01/31/2007
From:	Wetzel B Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML070330062 (10)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402-2801 January 31, 2007 10 CFR 50.55a U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Gentlemen:

In the Matter of ) Docket Nos. 50-327 Tennessee Valley Authority) 50-328 50-390 SEQUOYAH NUCLEAR PLANT (SQN) UNITS 1 AND 2 AND WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 - INSPECTION AND MITIGATION OF ALLOY 600/82/182 PRESSURIZER BUTT WELDS In October of 2006, while performing inspection of its pressurizer Alloy 600/82/182 butt welds in accordance with Materials Reliability Program (MRP)-1 39, a Pressurized Water Reactor (PWR) licensee discovered several circumferential indications in its pressurizer surge, safety and relief nozzles. Because of the potential importance of this issue, TVA is submitting this letter to commit to the following actions taken or planned for inspecting or mitigating Alloy 600/82/182 butt welds on pressurizer spray, surge, safety, and relief lines. These actions are as follows:

SQN Unit 1 Inspection of pressurizer Alloy 600/82/182 butt welds at Sequoyah Unit 1 has not yet been completed, but TVA intends to complete inspections and mitigation on these locations by the end of 1RFOC15 currently scheduled to end 10/30/2007. Details concerning Sequoyah Unit l's inspection and mitigation activities are provided in Enclosure 1. Results of completed inspections are also provided in Enclosure 1.

In addition to the inspection and mitigation actions described in Enclosure 1 tables, enhanced monitoring of the primary system leakage is used at SQN Unit 1.

Surveillance Instruction 0-SI-OPS-068-137.0, "Reactor Coolant System Water Inventory," is used for this enhanced leakage monitoring.

SQN Surveillance Instruction 0-SI-OPS-068-137.0, "Reactor Coolant System Water Inventory," is required to be performed every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, but is scheduled for performance every 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

Allo Printed on recycled paper

U.S. Nuclear Regulatory Commission Page 2 January 31, 2007 This procedure requires that actions be taken when the unidentified primary system leakage exceeds 0.25 gpm, increases more than 0.05 gpm from the previous measurement, or demonstrates a sustained increasing trend above typical values.

The required actions are as follows:

1. Evaluate recent activities for possible causes of the increase leakage,

2. Contact System Engineering, and

3. Initiate Abnormal Operating Procedure (AOP)-R.05, "RCS Leak and Leak Source Identification."

This enhanced guidance will provide adequate assurance that structural integrity is maintained and that any primary system pressure boundary leakage is discovered in a timely manner.

SQN Unit 2 Pressurizer Alloy 600/82/182 butt welds have been inspected and mitigated. Details concerning these actions are provided in Enclosure 2.

WBN Unit 1 Pressurizer Alloy 600/82/182 butt welds have been inspected. Details concerning the locations inspected are provided in Enclosure 3.

Future inspections of pressurizer butt welds at SQN Units 1 and 2 and WBN Unit 1 will be performed in accordance with industry guidance (MRP-1 39). The results of future inspection or mitigation of pressurizer Alloy 600/82/182 butt weld locations will be reported to the NRC within 60 days of startup from the outage during which they were performed. The NRC will be informed prior to revision to the information contained in this letter. The commitments made by this letter are provided in Enclosure 4. TVA's staff is available to meet with the NRC to discuss any of the information in this letter.

If there are any questions, please contact Rob Brown at (423) 751-7228.

Sincerely, Beth A. Wetzel Manager, Corporate Licensing and Industry Affairs Enclosure cc: See page 3

U.S. Nuclear Regulatory Commission Page 3 January 31, 2007 Enclosure cc: (Enclosure):

U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-8931 NRC Senior Resident Inspector U.S. Nuclear Regulatory Commission Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, TN 37379 NRC Senior Resident Inspector U.S. Nuclear Regulatory Commission Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, TN 37381 Brendan T. Moroney, Senior Project Manager U.S. Nuclear Regulatory Commission Mail Stop 08G9A One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739

ENCLOSURE 1 SQN UNIT 1 INSPECTION AND MITIGATION

SUMMARY

ALLOY 600/82/182 PRESSURIZER BUTT WELDS MRP-139 Volumetric Mitigation Nozzle Inspection Requirement Met Completed or to be or to be Met Completed Comments Function/ Susceptible Material Outage Start Date Outage Designation Description Designation Designation 4 inch - Spray: Nozzle to Safe end 1RFO15 October, 2007 IRFO15 The required MRP-139 volumetric inspection DM Weld No. weld and butter will be assisted by application of a full RCW-24-SE; structural weld overlay.

Valve Nos.

PCV-68-340B &

PCV-68-340D 14 inch - Surge: Nozzle to Safe end 1RFO15 October, 2007 1RFO15 This weld will be examined volumetrically in DM Weld weld and butter accordance with MRP-139 guidelines prior to RCW-29-SE application of a full structural weld overlay.

6 inch - Safety: Nozzle to Safe end 1RFO15 October, 2007 1RFO15 The required MRP-139 volumetric inspection DM Weld No. weld and butter will be assisted by application of a full RCW-27-SE; structural weld overlay.

Valve No.

VLV-68-563 6 inch - Safety: Nozzle to Safe end 1RFO15 October, 2007 1RFO15 The required MRP-139 volumetric inspection DM Weld No. weld and butter will be assisted by application of a full RCW-28-SE; structural weld overlay.

Valve No.

VLV-68-564 6 inch - Safety: Nozzle to Safe end 1RFO15 October, 2007 1RFO15 The required MRP-139 volumetric inspection DM Weld No. weld and butter will be assisted by application of a full RCW-25-SE; structural weld overlay.

Valve No.

VLV-68-565 6 inch - Relief: Nozzle to Safe end 1RFO1 5 October, 2007 1 RFO1 5 The required MRP-139 volumetric inspection DM Weld No. weld and butter will be assisted by application of a full RCW-26-SE; structural weld overlay.

Valve Nos.

PCV-68-340A &

PCV-68-334

Results of Previous Inspections The Table below (with the addition of the surge nozzle information) was provided in TVA's supplemental response to NRC Bulletin 2004-01 and summarizes the previously performed ASME Section XI examinations performed prior to the issue of MRP-1 39.

Note: The below Ultrasonic Testing (UT) inspections were performed prior to Performance Demonstration Initiative (PDI) qualification.

ASME Section Xl Examinations WELD NUMBER EXAM EXAM CYCLE EXAM REJECTABLE INDICATIONS CATEGORY AND METHOD/ (EXAM COVERAGE ITEM NUMBER REPORT DATE) ACHIEVED NUMBER RCW-24-SE spray B-F, B5.40 UT (R6930) U1C8 (4/97) UT 100 percent NO nozzle to safe-end B-F, B5.40 PT (R6914) U1 C8 (3/97) PT 100 percent NO RCW-29-SE B-F, B5.20 UT (R0402) U1C1 (10/82) UT 100 percent NO Pressurizer Surge B-F, B5.20 PT (R0257) U1C1 (10/82) PT 100 percent NO Nozzle B-F, B5.40 UT (R6887) U1C8 (3/97) UT 92 percent NO B-F, B5.40 PT (R6863) U1C8 (3/97) PT 100 percent NO RCW-27-SE B-F, B5.20 UT (R5064) U1C5 (10/91) UT 75 percent NO safety nozzle to safe-end B-F, B5.20 PT (R5173) UlC5 (10/91) PT 100 percent NO RCW-28-SE B-F, B5.20 UT (R5065) U1C5 (10/91) UT 75 percent NO safety nozzle to safe-end B-F, B5.40 PT (R7968) U1C12 (3/03) PT 100 percent NO - This was the third successive examination following cycle 5.

RCW-25-SE B-F, B5.20 UT (R2334) U1C3 (9/85) UT 80 percent NO safety nozzle to safe-end B-F, B5.20 PT (R5340) UIC5 (10/91) PT 100 percent NO RCW-26-SE B-F, B5.20 UT (R2333) UIC3 (9/85) UT 80 percent NO relief nozzle to safe-end B-F, B5.20 PT (R5340) U1C5 (10/91) PT 100 percent NO In addition, Bare Metal Visual (BMV) inspections were performed on each location listed in the above Table during 1RFO1 3 and 1RFO14. Neither of the visual inspections identified any leakage from the dissimilar metal welds.

ENCLOSURE 2 SQN UNIT 2 INSEPECTION AND MITIGATION

SUMMARY

ALLOY 600/82/182 PRESSURIZER BUTT WELDS Mitigation MRP-139 Volumetric Inspection Nozzle Requirement Met or to be Me be Completed Comet Suscptibe beCompetedComments Desination/

Function Susceptible Material Outage Start Date Outage Designation Description Designation Designation 4 inch - Spray: DM Nozzle to Safe end 2RF014 December, 2006 2RF014 The required MRP-139 volumetric Weld No.RCW-24-SE; weld and butter inspection was assisted by application of a Valve Nos. PCV full structural weld overlay.

340B & PCV-68-340D 14 inch - Surge: DM Nozzle to Safe end 2RF014 December, 2006 2RF014 This weld was volumetrically examined in Weld No. RCW-29-SE weld and butter accordance with MRP-1 39 guidelines prior to application of a full structural weld overlay. No recordable indications were found.

6 inch - Safety: DM Nozzle to Safe end 2RF014 December, 2006 2RF014 The required MRP-139 volumetric Weld No. RCW-26-SE; weld and butter inspection was assisted by application of a Valve No. VLV-68-563 _ full structural weld overlay.

6 inch - Safety: DM Nozzle to Safe end 2RF014 December, 2006 2RF014 The required MRP-139 volumetric Weld No. RCW-25-SE; weld and butter inspection was assisted by application of a Valve No. VLV-68-564 full structural weld overlay.

6 inch - Safety: DM Nozzle to Safe end 2RF014 December, 2006 2RF014 The required MRP-139 volumetric Weld No. RCW-28-SE; weld and butter inspection was assisted by application of a Valve No. VLV-68-565 full structural weld overlay.

6 inch - Relief: DM Nozzle to Safe end 2RF014 December, 2006 2RF014 The required MRP-139 volumetric Weld No. RCW-27-SE; weld and butter inspection was assisted by application of a Valve Nos. full structural weld overlay.

PCV-68-340A &

PCV-68-334

Results of Previous Inspections The Table below (with the addition of the surge nozzle information) was provided in TVA's supplemental response to NRC Bulletin 2004-01 and summarizes the previously performed ASME Section XI examinations performed prior to the issue of MRP-1 39.

Note: The below UT examinations were performed prior to PDI qualification.

ASME Section Xl Examinations EXAM CATEGORY EXAM CYCLE EXAM REJECTABLE WELD NUMBER AND ITEM METHOD/ (EXAM DATE) COVERAGE INDICATIONS NUMBER REPORT NUMBER ACHIEVED RCW-24-SE B-F, B5.40 UT (R5658) U2C7 (5196) UT 100 percent NO spray nozzle to safe-end B-F, B5.40 PT (R5624) U2C7 (5/96) PT 100 percent NO RCW-29-SE B-F, B5.20 UT (R0869) U2C1 (8/83) UT 100 percent NO Pressurizer surge nozzle B-F, B5.20 PT (R0870) U2C1 (8/83) PT 100 percent NO B-F, B5.40 UT (R5667) U2C7 (4/96) UT 100 percent NO B-F, B5.40 PT (R5574) U2C7 (4/96) PT 100 percent NO RCW-26-SE B-F, B5.20 UT (R3445, R3512) U2C3 (2/89) UT 70 percent NO safety nozzle to safe-end PT (R3391) U2C3 (2/89) PT 100 percent NO B-F, B5.20 RCW-25-SE B-F, B5.20 UT (R3444, R351 1) U2C3 (2/89) UT 70 percent NO safety nozzle to safe-end PT (R3391) U2C3 (2/89) PT 100 percent NO B-F, B5.20 RCW-28-SE B-F, B5.20 UT (R4472) U2C5 (4/92) UT 80 percent NO safety nozzle to safe-end B-F, B5.20 PT (R4544) U2C5 (3/92) PT 100 percent NO RCW-27-SE B-F, B5.20 UT (R4471) U2C5 (4/92) UT 80 percent NO relief nozzle to safe-end B-F, B5.20 PT (R4538) U2C5 (3/92) PT 100 percent NO In addition, BMV examinations were performed on each location listed in the above table during 2RF013 and 2RF014. Neither of the visual examinations identified any leakage from the dissimilar metal welds.

ENCLOSURE 3 WBN UNIT 1 INSPECTION AND MITIGATION

SUMMARY

ALLOY 600/82/182 PRESSURIZER BUTT WELDS Mitigation MRP-139 Volumetric Inspection Completed or Requirement Met or to be Met to be Completed Comments Functon Function /Material Susceptible Outage Start Date Outage Designation Description Designation Designation 4 inch - Spray: DM Nozzle to Safe 1RFO7 September, 2006 1RFO8 or TVA is currently in the process of evaluating Weld No. WP-1 1-SE; end weld and 1RFO9 mitigation strategies for this location.

Valve Nos. butter PCV-68-340B &

PCV-68-340D 14 inch - Surge: DM Nozzle to Safe 1RFO7 September, 2006 1RFO8 or TVA is currently in the process of evaluating Weld No. WP-10-SE end weld and 1RFO9 mitigation strategies for this location.

butter 6 inch - Safety: DM Nozzle to Safe 1RFO7 September, 2006 1RFO8 or TVA is currently in the process of evaluating Weld No. WP-15-SE; end weld and 1RFO9 mitigation strategies for this location.

Valve No. RFV-68-563 butter 6 inch - Safety: DM Nozzle to Safe 1RFO7 September, 2006 1RFO8 or TVA is currently in the process of evaluating Weld No. WP-13-SE; end weld and 1RFO9 mitigation strategies for this location.

Valve No. RFV-68-565 butter 6 inch - Safety: DM Nozzle to Safe 1RFO7 September, 2006 1RFO8 or TVA is currently in the process of evaluating Weld No. WP-14-SE; end weld and 1RFO9 mitigation strategies for this location.

Valve No. RFV-68-564 butter 6 inch - Relief: DM Nozzle to Safe 1RFO7 September, 2006 1RFO8 or TVA is currently in the process of evaluating Weld No. WP-12-SE; end weld and 1 RFO9 mitigation strategies for this location.

Valve Nos. PCV butter 340A & PCV-68-334 One-hundred percent coverage was obtained for the welds listed above and no recordable indications were found.

Results of Previous Inspections In addition to the above inspections, TVA reported in supplemental response to NRC Bulletin 2004-01 the completion of a BMV examination of each location listed in the above Table during 1 RFO5.

Since the response to 2004-01, TVA also performed a BMV examination of the above listed locations during 1 RFO6. Neither of the visual examinations identified any leakage from the dissimilar metal welds.

ENCLOSURE 4 LIST OF COMMITMENTS

1. Future inspections of pressurizer butt welds at SQN Unit 1 and 2 and WBN Unit I will be performed in accordance with industry guidance (MRP-139).

2. The results of future inspection or mitigations of pressurizer Alloy 600/82/182 butt weld locations will be reported to the NRC within 60 days of startup from the outage during which they were performed.