ULNRC-05373, Union Electric Co. Actions for Addressing Concerns Regarding Pressurizer Alloy 82/182 Butt Welds

Union Electric Co. Actions for Addressing Concerns Regarding Pressurizer Alloy 82/182 Butt Welds

ML070670457
Person / Time
Site:	Callaway
Issue date:	02/28/2007
From:	Fitzgerald D AmerenUE
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ULNRC-05373
Download: ML070670457 (6)

Text

AmerenUE PO Box 620 Callaway Plant Fulton, MO 65251 February 28, 2007 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop P1-137 Washington, DC 20555-0001 Ladies and Gentlemen: ULNRC-05373 DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.

UE ACTIONS FOR ADDRESSING CONCERNS REGARDING PRESSURIZER ALLOY 82/182 BUTT WELDS In October of 2006, while performing inspections of its pressurizer Alloy 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 potential importance of this issue, AmerenUE (Union Electric) submitted letter ULNRC-05360, "Inspection/Mitigation Plans for Alloy 82/182 Pressurizer Butt Welds," dated January 31, 2007 to notify the NRC of actions being taken or planned with regard to Alloy 82/182 butt welds on the pressurizer spray, surge, safety, and relief lines at Callaway Plant.

As described in the January 31 letter, a mitigation activity for addressing this issue is planned for Callaway Plant in which pre-emptive full structural weld overlays are to be applied to the nozzle-to-safe end dissimilar metal and safe-end-to piping stainless steel butt welds associated with the pressurizer and connected piping. This activity will be completed during the forthcoming refueling outage (RF-15) which is scheduled to commence on April 2, 2007. Completion of this activity during RF-15 was identified as a commitment in the January 31 letter.

Besides the planned mitigation activity, and as an interim action until commencement of RF- 15, AmerenUE also described in its January 31 letter how it will continue to monitor reactor coolant system (RCS) leakage (i.e., unidentified leakage) in accordance with the leakage monitoring program in place at Callaway.

The monitoring method, the overall sensitivity to an increase in RCS leakage, the thresholds levels at which. action would be taken, and the actions themselves that would be taken. if required,. were all summarized in the letter.

a subsidiaryof Ameren Corporation

ULNRC-05373 February 28, 2007 Page 2 Subsequent to submittal of the January 31 letter, however, and based on a telephone conference that was conducted between NRC and AmerenUE personnel on February 21, 2007, AmerenUE agreed to revise/enhance the RCS leakage monitoring program described in its January 31 letter and to formally commit to implementing an enhanced leakage monitoring program.

Accordingly, the enhanced RCS leakage monitoring program for Callaway Plant is described in Attachment 1 to this letter. The description/information provided in the attachment supersedes the description/information that was provided in the January 31 letter. Further, AmerenUE hereby commits to implementing the enhanced leakage monitoring program described in Attachment 1 on or by February 28, 2007. This commitment is identified as such in to this letter.

It should .be noted that the commitment and descriptive information provided in regard to the mitigation activity planned for RF-15, as well as the summary information that was provided regarding the bare metal visual inspections that were performed at Callaway for the pressurizer nozzle welds, remain unchanged from what was contained in the January 31 letter. That information and commitment are thus not repeated in this letter. However, one additional commitment should be made in light of the fact that AmerenUE's January 31 letter did not mention reporting of the details associated with the follow-up inspections to be performed for the pressurizer weld overlays after installation during RF-15, as desired by the NRC. Such a report is to be provided within 60 days following restart from RF-15. A commitment to provide the report is hereby made in this letter, and this commitment is included in Attachment 2.

For any questions regarding the information provided in this letter or its attachments, please contact me at 573-676-8763 or David E. Shafer at either 314-554-3104 or 573-676-4722. AmerenUE hereby notes that the NRC will be informed if any of the information contained in this letter or its attachments is to be revised. (This is identified as a commitment in Attachment 2.)

Sincerely, David T. Fitzgerald Manager - Regulatory Affairs TBE/jdg Attachments: 1. Enhanced Reactor Coolant System (RCS) Leakage Monitoring Program for Callaway Plant

2. List of Commitments

ULNRC-05373 February 28, 2007 Page 3 cc: Mr. Bruce S. Mallett Regional Administrator U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-4005 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Jack N. Donohew (2 copies)

Licensing Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop O-7D1 Washington, DC 20555-2738 Missouri Public Service Commission Governor Office Building 200 Madison Street PO Box 360 Jefferson City, MO 65102-0360

ULNRC-05373 February 28, 2007 Page 4 bcc: C. D. Naslund (w/a) D. J. Maxwell (w/a)

A. C. Heflin (w/a) M. G. Hoehn II (w/a)

D. T. Fitzgerald (w/a) K. A. Mills (w/a)

T. E. Herrmann (w/a) T. B. Elwood (w/a)

L. E. Thibault (w/a) G. A. Forster (w/a)

G. A. Hughes (w/a) A160.0761 D. E. Shafer (w/a)

S. L. Gallagher (100)

L. M. Belsky (NSRB)

S. L. Klang (w/a)

D. M. Stepanovic (w/a)

Certrec Corporation 4200 South Hulen, Suite 630 Fort Worth, TX 76109 (Certrecreceives ALL attachments as long as they are non-safeguards and public disclosed).

Send the following without attachments:

Ms. Diane M. Hooper Mr. Dennis Buschbaum Supervisor, Licensing TXU Power WCNOC Comanche Peak SES P.O. Box 411 P.O. Box 1002 Burlington, KS 66839 Glen Rose, TX 76043 Mr. Scott Bauer Mr. Stan Ketelsen Regulatory Affairs Manager, Regulatory Services Palo Verde NGS Pacific Gas & Electric P.O. Box 52034, Mail Stop 104/5/536 Mail Station 7636 P.O. Box 56 Phoenix, AZ 85072-2034 Avila Beach, CA 93424 Mr. Scott Head Mr. John O'Neill Supervisor, Licensing Pillsbury Winthrop Shaw Pittman LLP South Texas Project NOC 2300 N. Street N.W.

Mail Code N5014 Washington, DC 20037 P.O. Box 289 Wadsworth, TX 77483

Attachment 1 to ULNRC-05373 Enhanced Reactor Coolant System (RCS)

Leakage Monitoring Program for Callaway Plant RCS Leakage RCS Leakage RCS Leakage Monitoring Monitoring Action Monitoring Reporting Frequency (1)(2) Levels Actions _

Daily (i.e., at least once (1) A 0.1 gpm increase With a leakage increase Report details of bare per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) during in unidentified leakage at or above the metal visual inspection MODES 1, 2, 3. from the previous day, threshold value and results (if bare metal such that the additional sustained for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> inspection is required leakage is sustained for [per (1) or (2) at left], per the specified Action 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, with at least place the unit in MODE at left) within 60 days of 0.1 gpm not confirmed 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in the unit restart.

from sources other than MODE 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> pressurizer nozzle and perform a bare welds. metal visual inspection of the pressurizer surge, OR spray, safety, and relief nozzle butt welds (2) A 0.25 gpm increase containing alloy 82/182 above a baseline leak material.

rate for unidentified leakage, such that the additional leakage is sustained for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, with at least 0.25 gpm not confirmed from sources other than the pressurizer nozzle welds.(3 )

Notes:

1. The provision of Technical Specification (TS) Surveillance Requirement (SR) 3.0.2 (i.e., 25% overrun) is applicable to the Frequency specified here.

2. As specified in Callaway TS 3.4.13, "RCS Operational Leakage," performance of the RCS water inventory balance per SR 3.4.13.1 (for verifying that RCS operational leakage is within limits) is not required until 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after establishing steady-state operation upon restart. The basis for this provision (and therefore the provision itself) applies here as well, in the event of an unplanned plant shutdown and restart prior to RF-1 5.

3. During the telecon conducted with NRC staff personnel on February 21, 2007, it was discussed how the baseline leak rate would be established from values that were recorded during the first 7 days after attaining steady-state full-power operation upon restart from RF-14 (Fall 2005). Subsequent to the telecon, however, it was determined that the discussed approach (which would have been based on values obtained from 11/26/05 to 12/4/05) would have yielded a non-conservatively high baseline value due to the more extended time it took achieve an average steady-state unidentified leakage value after restart from RF-14.

Instead, values obtained during the period from 12/6/05 to 12/31/05 were used to determine the average unidentified leakage subsequent to RF-14, which established a more conservative (lower) baseline value for the purposes of the enhanced leakage monitoring program. This approach was discussed and accepted by the NRC via electronic mail on 2/22/07.

Attachment 2 to ULNRC-05373 LIST OF COMMITMENTS The following table identifies actions committed to by AmerenUE in this document (letter). Any other statements in this document (letter) are provided for information purposes and are not considered commitments. Please direct questions regarding this commitment to David E. Shafer, Superintendent, Licensing at either 314-554-3104 or 573-676-4722.

COMMITMENT Due Date/Event Callaway Plant will implement and conform to the enhanced RCS To begin on or by leakage monitoring program, including the specified shutdown February 28, 2007 actions as required, which is described in Attachment 1. and continue until plant shutdown for RF- 15.

Details concerning results of the follow-up inspections to be Within 60 days performed on the pressurizer weld overlays installed during RF-15 following plant will be reported to the NRC. restart from RF-15.

The NRC will be informed if AmerenUE revises any of the Prior to revision of information contained in this letter (ULNRC-05373) (including its the information.

attachments).