CNRO-2007-00007, Inspection and Mitigation of Alloy 600/82/182 Pressurizer Butt Welds

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

ML070610349
Person / Time
Site:	Arkansas Nuclear
Issue date:	02/22/2007
From:	Burford F Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNRO-2007-00007
Download: ML070610349 (9)

Text

Entergy Operations, Inc.

1340 Echelon Parkway Jackson, Mississippi 39213-8298 UP-/ Tel 601-368-5758 F. G. Burford Acting Director Nuclear Safety & Licensing CNRO-2007-00007 February 22, 2007 U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Inspection and Mitigation of Alloy 600/82/182 Pressurizer Butt Welds Arkansas Nuclear One, Units 1 and 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 and NPF-29

REFERENCE:

Entergy Operations, Inc. letter CNRO-2007-00003 to the NRC, Inspection and Mitigation of Alloy 600/821182 PressurizerButt Welds, dated January 31, 2007

Dear Sir or Madam:

In October 2006, while performing inspections of its pressurizer Alloy 600/82/182 butt welds in accordance with MRP-139, a PWR licensee discovered several circumferential indications in its pressurizer surge, safety, and relief nozzles. Because of the importance of this issue, Entergy Operations, Inc. (Entergy) notified the NRC staff of actions planned for Arkansas Nuclear One, Unit 1 (ANO-1) to mitigate Alloy 600/82/182 butt welds on pressurizer spray, surge, and relief lines via the referenced letter.

Regarding Arkansas Nuclear One, Unit 2 (ANO-2), Entergy replaced the ANO-2 pressurizer during the fall 2006 refueling outage (2R18) with one manufactured of materials resistant to primary water stress corrosion cracking (PWSCC). Further inspections to address concerns with Alloy 600/82/182 butt welds are not necessary.

On February 14, 2007, representatives from Entergy and the NRC staff discussed the ANO-1 action plan. As a result of that call, Entergy has revised its action plan and commitments.

This letter supersedes the referenced letter.

Entergy will inform the NRC prior to revising any of the committed actions identified in . Our staff is available to meet with the NRC to discuss any of the information in this letter. Should you have any questions pertaining to this letter, please contact Guy Davant at (601) 368-5756.

CNRO-2007-00007 Page 2 of 2 This letter contains commitments identified in Enclosure 2. These commitments supersede those provided in the referenced letter.

Sincerely, FGB/GHD/ghd

Enclosures:

1. Actions Planned to Mitigate Alloy 600/82/182 Pressurizer Butt Welds at ANO-1

2. Licensee-Identified Commitments cc: Mr. W. A. Eaton (ECH)

Mr. T. G. Mitchell (ANO)

Dr. Bruce S. Mallet Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 U.S. Nuclear Regulatory Commission Attn: Ms. F. E. Saba MS 0-8 B1 Washington, DC 20555-0001

ENCLOSURE 1 CNRO-2007-00007 ACTIONS PLANNED TO MITIGATE ALLOY 600/82/182 PRESSURIZER BUTT WELDS AT ANO-1 to CNRO-2007-00007 Page 1 of 3 ACTIONS PLANNED TO MITIGATE ALLOY 600/82/182 PRESSURIZER BUTT WELDS AT ANO-1 Mitigation activities of the pressurizer Alloy 600/82/182 dissimilar metal (DM) butt welds at Arkansas Nuclear One, Unit 1 (ANO-1) have not yet been completed, but are scheduled to be completed during the upcoming spring 2007 refueling outage (1 R20). At that time, Entergy will visually inspect and mitigate the pressurizer Alloy 600/82/182 butt welds by installing full structural weld overlays on these welds. The results of these mitigation activities will be reported to the NRC within 60 days following startup from 1 R20. Details concerning ANO-I's mitigation activities are provided in Table 1.

In addition, by letter dated January 12, 2007, Entergy Operations, Inc. (Entergy) proposed to the NRC staff an alternative to ASME Code requirements for weld overlay repairs. This request, ANO1-R&R-010, contains details regarding the weld overlay activities. Future inspections of these pressurizer butt weld overlays will be performed in accordance with ANOl -R&R-010.

If ANO-1 should shut down due to primary system unidentified leakage prior to 1 R20, Entergy shall either confirm that the leak does not originate from the pressurizer DM butt welds (including quantifying the leak from the suspected location) or will perform, prior to restart, a bare metal visual examination of these weld locations to determine whether the leakage originated at these locations. ANO-1 will report the results of these inspections to the NRC within 60 days of start-up from the associated outage.

Until the pressurizer DM butt welds are mitigated, Entergy will revise the ANO-1 primary system leakage monitoring program to include the following actions:

• If unidentified leakage exceeds either of the two limits below and is sustained for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and if the source of the leakage cannot be verified to be from a location other than the pressurizer DM butt welds, then ANO-1 will shut down and perform a bare metal visual examination of all such weld locations.

>. 0.25 gpm greater than a baseline value.

The baseline value should be established using leakage rates measured within 7 days after achieving 100% reactor power following the most recent bare metal visual examination of the pressurizer Alloy 600/82/182 butt weld locations.

• 0.1 gpm increase over the preceding day's 5-day average unidentified leakage.

" Following initiation of a shutdown, the plant shall be in HOT STANDBY in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN in the next 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

" Should the leakage increase return to within limits or be confirmed to be from a source other than the pressurizer DM butt welds, then the shutdown actions may be halted and a return to normal operating conditions may commence.

to CNRO-2007-00007 Page 2 of 3 These actions will be incorporated into the ANO-1 primary system leakage monitoring program by M~rch 1, 2007 and remain in place until the mitigation actions for the pressurizer DM butt welds are completed.

The methods of leak detection described above are sufficient to ensure RCS leakage is readily detected and corrective actions initiated prior to conditions degrading to a level resulting in a failure of the RCS pressure boundary.

to CNRO-2007-00007 Page 3 of 3 TABLE 1 Mitigation Summary for ANO-1 Alloy 600/82/182 Pressurizer Butt Welds MRP-139 Volumetric Mitigation to be Nozzle Inspection Requirement to Completed be Met Comments Function / Susceptible Outage Outage Designation Material Designation Start Date Designation Description DesignationDesignation Two welds:

Nozzle-to-safe end (1) Carbon steel nozzle welded to A600 1 R20 Spring 2007 1 R20 safe end; weld, A600 safe yend, and safe end- (2) A600 safe end welded to stainless to-pipe weld steel pipe.

Welds are A600/82/182.

Nozzle-to-safe end 1R20 Spring 2007 1R20 Carbon steel nozzle to stainless steel Surge weld only safe end using A600/82/182 Electromatic Nozzle-to-flange Carbon steel nozzle to stainless steel Relief Valve weld only 1R20 Spring 2007 1R20 flange using A600/82/182

1. PSV1 000 Code Safety Nozzle-to-flange 1R20 Spring 2007 1R20 Carbon steel nozzle to stainless steel Valve weld only flange using A600/82/182

1. PSV-1001 Code Safety Nozzle-to-flange Carbon steel nozzle to stainless steel Valve weld only 1R20 Spring 2007 1R20 flange using A600/82/182

1. PSV-1002

ENCLOSURE 2 CNRO-2007-00007 LICENSEE-IDENTIFIED COMMITMENTS

Enclosure 2 to CNRO-2007-00007 Page 1 of 2 LICENSEE-IDENTIFIED COMMITMENTS

1. Entergy will inform the NRC prior to revising V-any of the committed actions identified in Until the end of Enclosure 1. 1R20

2. During the upcoming spring 2007 refueling " End of 1 R20 outage at ANO-1 (1 R20), Entergy will visually inspect and mitigate the pressurizer Alloy 600/82/182 butt welds by installing full structural weld overlays on these welds.

3. The results of the ANO-1 mitigation activities 60 days following will be reported to the NRC within 60 days startup from 1R20 following startup from 1R20.

4. If ANO-1 should shut down due to primary /

system unidentified leakage prior to 1R20, Until the end of Entergy shall either confirm that the leak does 1R20 not originate from the pressurizer DM butt welds (including quantifying the leak from the suspected location) or will perform, prior to restart, a bare metal visual examination of these weld locations to determine whether the leakage originated at these locations.

5. ANO-1 will report the results of the inspections V/

identified in Item #4 within 60 days of start-up Until the end of from the associated outage. 1R20

Enclosure 2 to CNRO-2007-00007 Page 2 of 2 COM1MITMENT

6. Until the pressurizer DM butt welds are V/

mitigated, Entergy will revise the ANO-1 Until the end of primary system leakage monitoring program to 1R20 include the following actions:

" If unidentified leakage exceeds either of the two limits below and is sustained for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and if the source of the leakage cannot be verified to be from a location other than the pressurizer DM butt welds, then ANO-1 will shutdown and perform a bare metal visual examination of all such weld locations.

> 0.25 gpm greater than a baseline value.

The baseline value should be established using leakage rates measured within 7 days after achieving 100% reactor power following the most recent bare metal visual examination of the pressurizer Alloy 600/82/182 butt weld locations.

> 0.1 gpm increase over the preceding day's 5-day average unidentified leakage.

• Following initiation of a shutdown, the plant shall be in HOT STANDBY in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN in the next 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

• Should the leakage return to within limits or be confirmed to be from a source other than the pressurizer DM butt welds, then the shutdown actions may be halted and a return to normal operating conditions may commence.

7. The actions specified in Item #6, above, will be / March 1, 2007 incorporated into the ANO-1 primary system leakage monitoring program by March 1, 2007 and remain in place until mitigation actions for the pressurizer DM butt welds are completed.