ML070610585

Confirmatory Action Letter NRR-07-001, Pressurizer Dissimilar Metal (Alloy 82/182) Butt Weld Inspections

ML070610585
Person / Time
Site:	Seabrook
Issue date:	03/12/2007
From:	Dyer J Office of Nuclear Reactor Regulation
To:	St.Pierre G Nuclear Management Co
References
NRR-07-001
Download: ML070610585 (5)

Text

March 12, 2007 CAL No. NRR-07-001 Mr. Gene F. St. Pierre Site Vice President c/o James M. Peschel Seabrook Station Seabrook, NH 03874

SUBJECT:

CONFIRMATORY ACTION LETTER, SEABROOK STATION, UNIT NO. 1

Dear Mr. St. Pierre:

This letter confirms commitments by Florida Power & Light Company and FPL Energy Seabrook, LLC in regard to Alloy 82/182 butt welds in the pressurizer at Seabrook Unit No. 1.

The discovery, in October 2006, of five circumferential indications in three dissimilar metal (DM) welds on the pressurizer at the Wolf Creek Generating Station (Wolf Creek) raised safety concerns based on the size and location of the indications. At Wolf Creek, three indications were in the pressurizer surge nozzle-to-safe end weld, and two separate indications were in the safety and relief nozzle-to-safe end welds. These findings also indicated that significant concerns might exist with the inspection schedules for addressing the pressurizer weld concerns issued by the industry-sponsored Materials Reliability Program (MRP), in Primary System Piping Butt Weld Inspection and Evaluation Guideline (MRP-139).

The Nuclear Regulatory Commission (NRC) is concerned about the pressurizer surge nozzle-to-safe end weld indications, as this is the first time that multiple circumferential primary water stress-corrosion cracking (PWSCC) indications have been identified in a weld. This condition calls into question the degree of safety margin present in past structural integrity evaluations for flawed DM welds susceptible to PWSCC, since multiple stress-corrosion cracking flaws may grow independently and ultimately grow together, significantly reducing the time from flaw initiation to leakage or rupture. The size of the relief nozzle-to-safe end flaw is also of concern, as this flaw has a much larger aspect ratio than those assumed in the estimates used to establish the basis for completing the baseline inspections required by the industry-sponsored MRP. Larger aspect ratios could result in achieving a critical flaw size and rupture before the onset of detectable leakage.

The long-term resolution of this issue is expected to involve changes to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), and will involve changes to the NRC regulations in Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section 50.55a, Codes and standards. The development of the NRC regulations, whether the rule adopts the ASME Code standards or defines separate requirements, will likely benefit from additional operating experience, continuing assessments, and analysis being conducted by the NRC and the MRP.

G. St. Pierre Until NRC regulations are revised, it is necessary to establish a minimum set of enhanced reactor coolant system (RCS) DM butt weld inspection expectations for nickel-based Alloy 82/182 pressurizer surge, spray, safety, and relief nozzle butt welds, including safe end welds, to supplement existing inspection and other requirements of the ASME Code and NRC regulations. In addition, enhanced monitoring of RCS leakage is needed to promptly identify any through-wall flaws in the pressurizer surge, spray, safety, or relief nozzle DM butt welds or safe end DM butt welds to prevent additional degradation from occurring. The above actions provide reasonable assurance that there is no undue risk to the health and safety of the public while the NRC regulations are revised.

The NRC communicated the need for near-term enhancements to the industry through public meetings held on November 30, 2006, December 20, 2006, and February 2, 2007.

Licensees submitted letters voluntarily committing to the enhanced inspection and leakage monitoring requirements. After teleconferences with specific licensees held between February 12 through February 23, 2007, the licensees submitted supplemental commitment letters addressing the NRC staffs concerns regarding inspection, compensatory actions, and reporting.

In your letter dated February 21, 2007 (Agencywide Documents Access and Management System (ADAMS) ML070530548), you described actions you will take at the Seabrook Station for the pressurizer DM butt welds containing Alloy 82/182 material.

These commitments address: 1) completion schedules for inspection/mitigation of the welds;

2) RCS leak monitoring frequency, action levels, and actions; and 3) reporting requirements.

The NRC staff has reviewed these actions and commitments and agrees the actions and commitments are appropriate to address the potential of PWSCC of the applicable pressurizer DM butt welds containing Alloy 82/182 material with clarifications on two of the commitments as indicated in bold below regarding acceleration of weld mitigation and reporting.

• FPL Energy Seabrook will accelerate the outage currently scheduled for April 2008 into 2007 if the calculations being developed by NEI and MRP do not demonstrate an adequate level of safety to the NRC. This schedule could also be accelerated if new information is obtained during upcoming inspections at other plants that challenge current industry assumptions.

• FPL Energy Seabrook shall report results of any bare metal visual inspections required, and will provide the results of the pressurizer butt weld inspection or mitigation actions to NRC 60 days after plant start up.

These clarifications were discussed with and agreed upon by you during a telephone discussion on March 6, 2007, with Michele Evans, Director, Division of Component Integrity, Office of Nuclear Reactor Regulation.

Pursuant to Section 182 of the Atomic Energy Act, 42 U.S.C. 2232, you are required to:

1) Notify me immediately if your understanding differs from that set forth above;

G. St. Pierre 2) Notify me if for any reason you cannot complete the actions and commitments within the specified schedule and advise me in writing of your modified schedule in advance of the change; and

3) Notify me in writing when you have completed the actions and commitments addressed in this Confirmatory Action Letter.

Issuance of this Confirmatory Action Letter does not preclude issuance of an order formalizing the above commitments or requiring other actions on the part of the licensee; nor does it preclude the NRC from taking enforcement action for violations of NRC requirements that may have prompted the issuance of this letter. In addition, failure to take the actions addressed in this Confirmatory Action Letter may result in enforcement action.

In accordance with 10 CFR 2.390 of the NRC's "Rules of Practice," a copy of this letter and your response will be made available electronically for public inspection in the NRC Public Document Room or from the NRCs ADAMS, accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html. To the extent possible, your response should not include any personal privacy, proprietary, or safeguards information so that it can be made available to the Public without redaction. If personal privacy or proprietary information is necessary to provide an acceptable response, then please provide a bracketed copy of your response that identifies the information that should be protected and a redacted copy of your response that deletes such information. If you request withholding of such material, you must specifically identify the portions of your response that you seek to have withheld and provide in detail the bases for your claim of withholding (e.g., explain why the disclosure of information will create an unwarranted invasion of personal privacy or provide the information required by 10 CFR 2.390(b) to support a request for withholding confidential commercial or financial information). If safeguards information is necessary to provide an acceptable response, please provide the level of protection described in 10 CFR 73.21.

Sincerely,

/RA/

J.E. Dyer, Director Office of Nuclear Reactor Regulation Docket No. 50-443 License No. NPF-86 cc: See next page

ML070610585

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Seabrook Station, Unit No. 1 cc:

Mr. J. A. Stall Ms. Cristine McComb, Director Senior Vice President, Nuclear and ATTN: John Giarrusso Chief Nuclear Officer Massachusetts Emergency Management Agency Florida Power & Light Company 400 Worcester Road P.O. Box 14000 Framingham, MA 01702-5399 Juno Beach, FL 33408-0420 Ms. Kelly Ayotte, Attorney General Mr. Peter Brann Mr. Orvil Fitch, Deputy Attorney General Assistant Attorney General 33 Capitol Street State House, Station #6 Concord, NH 03301 Augusta, ME 04333 Mr. Christopher M. Pope, Director Resident Inspector Homeland Security & Emergency Mgmt.

U.S. Nuclear Regulatory Commission New Hampshire Department of Safety Seabrook Nuclear Power Station Bureau of Emergency Management P.O. Box 1149 33 Hazen Drive Seabrook, NH 03874 Concord, NH 03301 Town of Exeter Mr. M. S. Ross, Managing Attorney 10 Front Street Florida Power & Light Company Exeter, NH 03823 P.O. Box 14000 Juno Beach, FL 33408-0420 Regional Administrator, Region I U.S. Nuclear Regulatory Commission Mr. Rajiv S. Kundalkar 475 Allendale Road Vice President - Nuclear Engineering King of Prussia, PA 19406 Florida Power & Light Company P.O. Box 14000 Office of the Attorney General Juno Beach, FL 33408-0420 One Ashburton Place, 20th Floor Boston, MA 02108 James M. Peschel Regulatory Programs Manager Board of Selectmen FPL Energy Seabrook, LLC Town of Amesbury PO Box 300 Town Hall Seabrook, NH 03874 Amesbury, MA 01913 Ms. Marjan Mashhadi Mr. Robert Poole Senior Attorney Federal Emergency Management Agency Florida Power & Light Company Region I 801 Pennsylvania Ave., NW Suite 220 99 High Street, 6th Floor Washington, DC 20004 Boston, MA 02110 Mr. Tom Crimmins Mr. Mark E. Warner Polestar Applied Technology Vice President, Nuclear Operations Support One First Street, Suite 4 Florida Power & Light Company Los Altos, CA 94019 P.O. Box 14000 Juno Beach, FL 33408-0420