ML070320127

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

ML070320127
Person / Time
Site:	Calvert Cliffs
Issue date:	01/30/2007
From:	Spina J Constellation Energy Group
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML070320127 (5)

Text

James A. Spina Calvert Cliffs Nuclear Power Plant, Inc.

Vice President 1650 Calvert Cliffs Parkway Lusby, Maryland 20657 410.495.5200 410.495.3500 Fax 0 Constellation Energy, Generation Group January 30, 2007 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit Nos. 1 & 2; Docket Nos. 50-317 & 50-318 Inspection and Mitigation of Alloy 600/82/182 Pressurizer Butt Welds In October 2006, while performing inspections of its pressurizer Alloy 82/182 butt welds in accordance with Materials Reliability Program (MRP)-139, "Material Reliability Program: 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, Calvert Cliffs Nuclear Power Plant, Inc. (CCNPP) 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 and relief lines.

All pressurizer Alloy 600/82/182 butt welds at CCNPP Unit 1 have been inspected and mitigated. Details concerning the locations inspected and mitigated are provided in the attached table (Attachment 1).

Inspection of all pressurizer Alloy 600/82/182 butt welds at CCNPP Unit 2 is not complete, but we intend to complete all our inspection and mitigation activities on these locations during the spring 2007 outage, scheduled to begin February 25, 2007. Details concerning the inspection and mitigation activities are provided in the attached table (Attachment 1). Future inspections of pressurizer butt welds at both CCNPP units will be performed in accordance with industry guidance (MRP-139). The results of future inspections or mitigations of Alloy 600/82/182 butt welds locations will be reported to the NRC within 60 days of startup from the outage during which they were performed.

Due to the short period of time between now and the Unit 2 refueling outage, enhanced guidance for monitoring primary system leakage will not be developed. Our existing guidance for monitoring primary system leakage requires a daily measurement of primary system leakage and has actions beginning at an unidentified leak rate of 0.15 gpm. This guidance provides adequate assurance that structural integrity is maintained and that any primary system pressure boundary leakage is discovered in a timely manner.

The Nuclear Regulatory Commission will be informed, as appropriate, if CCNPP Units 1 or 2 revises any of the information contained in this letter.

Awlo

Document Control Desk January 30, 2007 Page 2 Should you have questions regarding this matter, please contact Mr. Jay S. Gaines at (410) 495-5219.

Very truly yours, JAS/PSF/bjd

Attachment:

(1) Inspection and Mitigation Sum r for Alloy 600/82/182 Pressurizer Butt Welds 11 DfD'A+T/

r% 1111 cc -. V. CIR LL, INe .A.-

S. J. Collins, NRC R. I. McLean, DNR

ATTACHMENT (1)

INSPECTION AND MITIGATION

SUMMARY

FOR ALLOY 600/82/182 PRESSURIZER BUTT WELDS Calvert Cliffs Nuclear Power Plant, Inc.

January 30, 2007

ATTACHMENT (1)

INSPECTION AND MITIGATION

SUMMARY

FOR ALLOY 600/82/182 PRESSURIZER BUTT WELDS Table 1 - Calvert Cliffs Unit 1 MRP-139 Volumetric Inspection Mitigation Nozzle Requirement Met or to be Met Completed Susceptible Outage Start DateComments Function / Designation Material Outage StartnDate Description Designation (MM/YYYY) Outage Designation Spray Nozzle-to-Safe End 2006 RFO 02/2006 2006 RFO Note 1, 2 Weld Only Surge Nozzle-to-Safe End 2006 RFO 02/2006 2006 RFO Note 2, 3 Weld Only Safety/Relief to line no. Nozzle-to-Safe End 2006 RFO 02/2006 2006 RFO Note 2, 3 4CC10-1005 Weld Only Safety/Relief to line no. Nozzle-to-Safe End 2006 RFO 02/2006 2006 RFO Note 2, 4 4CC1O-1006 Weld Only Note 1: Stress improvement mitigation was performed. Ultrasonic testing (UT) examinations meeting PDI qualification requirements were performed before and after stress improvement with no recordable indications. Coverage for UT examinations was 100% for axial scanning and 59% for circumferential scanning relative to the examination volume defined in MRP-139.

Note 2: Bare metal visual inspection performed during the spring 2004 refueling outage, finding no indications of leakage.

Note 3: Stress improvement mitigation was performed. Ultrasonic testing examinations meeting PDI qualification requirements were performed before and after stress improvement with no recordable indications. Coverage for UT examinations was 90% or greater of the examination volume defined in MRP-139.

Note 4: Stress improvement mitigation was performed. Ultrasonic testing examinations meeting PDI qualification requirements were performed before and after stress improvement. Axial indication found during pre-stress improvement UT exam and sized using PDI qualified sizing procedures. The indication was 0.1 inches in depth and 0.6 inches in length, and located at the inner diameter of the buttering, extending to the buttering/weld metal interface. The weld thickness is 1.3 inches. Examination results for welds having indications have been transmitted to NRC in References 1 and 2. Coverage for UT examinations was 90% or greater of the examination volume defined in MRP-139.

References:

(1) Letter from Mr. J. A. Spina (CCNPP) to Document Control Desk (NRC), dated May 31, 2006, ASME Code Section XI Flaw Evaluation of Dissimilar Metal Weld Flaws Identified by Ultrasonic Testing (2) Letter from Mr. J. A. Spina (CCNPP) to Document Control Desk (NRC), dated December 22, 2006, Response to NRC Request for Additional Information I

ATTACHMENT (1)

INSPECTION AND MITIGATION

SUMMARY

FOR ALLOY 600/82/182 PRESSURIZER BUTT WELDS Table 2 - Calvert Cliffs Unit 2 MRP-139 Volumetric Inspection Mitigation Nozzle Requirement Met or to be Met Completed or to be Outage Start Date Susceptible Function / Designation Material Outage Designation Description Designation (MM/YYYY)

Spray Nozzle-to-Safe End 2007 RFO 02/2007 2007 RFO Note 1, 2, 3 Weld Only Surge Nozzle-to-Safe End 2007 RFO 02/2007 2007 RFO Note 1, 2 Weld Only Safety/Relief to line no. Nozzle-to-Safe End 2007 RFO 02/2007 2007 RFO Note 1, 2, 3 4CC1O-2005 Weld Only Safety/Relief to line no. Nozzle-to-Safe End 2007 RFO 02/2007 2007 RFO Note 1, 2, 3 4CC 10-2006 Weld Only Note I: Stress improvement mitigation is planned. Ultrasonic testing examinations meeting PDI qualification requirements will be performed before and after stress improvement. Full structural weld overlay will be performed if indications in excess of the stress improvement criteria are found in the pre-stress improvement UT examination.

Note 2: Bare metal visual inspection performed during the spring 2005 refueling outage, finding no indications of leakage.

Note 3: An ultrasonic examination meeting PDI qualification requirements was performed during 2RFO15 in Spring 2005, finding no recordable indications. Coverage for UT examinations was 90% or greater of the examination volume defined in MRP-1 39.

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