ML070730470
| ML070730470 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/20/2007 |
| From: | Dyer J Office of Nuclear Reactor Regulation |
| To: | Bezilla M FirstEnergy Nuclear Operating Co |
| Wengert, Thomas | |
| References | |
| TAC MD4148, NRR-07-017 | |
| Download: ML070730470 (7) | |
Text
CAL No. NRR-07-017 March 20, 2007 Mr. Mark B. Bezilla Site Vice President FirstEnergy Nuclear Operating Company Davis-Besse Nuclear Power Station Mail Stop A-DB-3080 5501 North State Route 2 Oak Harbor, OH 43449-9760
SUBJECT:
CONFIRMATORY ACTION LETTER - DAVIS-BESSE NUCLEAR POWER STATION (TAC NO. MD4148)
Dear Mr. Bezilla:
This letter confirms commitments by FirstEnergy Nuclear Operating Company (FENOC) regarding Alloy 82/182 butt welds in the pressurizer at Davis-Besse Nuclear Power Station.
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.
M. Bezilla 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 28, 2007 (Agencywide Documents Access & Management System (ADAMS) Accession Number ML070660476) you described actions you will take at the Davis-Besse Nuclear Power Station for the pressurizer dissimilar metal 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;
- 3) reporting requirements, and 4) reinspection frequencies.
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 dissimilar metal butt welds containing Alloy 82/182 material.
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;
- 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
M. Bezilla 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. 50-346 License No. NPF-3 cc: See next page
ML070730470 NRR-106 OFFICE CPNB DCI LPL3-2/PM LPL3-2/LA LPL3-2/BC TECH DIRS/TA ED NAME TLupold ESullivan TWengert EWhitt RGibbs HChang RPascarelli DATE 3/16/07 3/16/07 3/14/07 3/14/07 3/14/07 2/28/07 3/19/07 OFFICE CPNB/BC DRP/D RGN 3 DORL/D DCI/D AD:DES NRR/D NAME TChan MSatorius CHaney MEvans JGrobe JDyer DATE 3/16/07 3/16/07 3/19/07 3/16/07 3/20/07 3/20/07 Davis-Besse Nuclear Power Station, Unit 1 cc:
Manager, Site Regulatory Compliance Attorney General FirstEnergy Nuclear Operating Company Office of Attorney General Davis-Besse Nuclear Power Station 30 East Broad Street Mail Stop A-DB-3065 Columbus, OH 43216 5501 North State Route 2 Oak Harbor, OH 43449-9760 President, Board of County Commissioners of Ottawa County Director, Ohio Department of Commerce Port Clinton, OH 43252 Division of Industrial Compliance Bureau of Operations & Maintenance President, Board of County 6606 Tussing Road Commissioners of Lucas County P.O. Box 4009 One Government Center, Suite 800 Reynoldsburg, OH 43068-9009 Toledo, OH 43604-6506 Regional Administrator, Region III The Honorable Dennis J. Kucinich U.S. Nuclear Regulatory Commission United States House of Representatives Suite 210 Washington, D.C. 20515 2443 Warrenville Road Lisle, IL 60532-4352 The Honorable Dennis J. Kucinich United States House of Representatives Resident Inspector 14400 Detroit Avenue U.S. Nuclear Regulatory Commission Lakewood, OH 44107 5503 North State Route 2 Oak Harbor, OH 43449-9760 Gary R. Leidich President and Chief Nuclear Officer Stephen Helmer FirstEnergy Nuclear Operating Company Supervisor, Technical Support Section Mail Stop A-GO-19 Bureau of Radiation Protection 76 South Main Street Ohio Department of Health Akron, OH 44308 35 East Chestnut Street, 7th Floor Columbus, OH 43215 Joseph J. Hagan Senior Vice President of Operations and Carol OClaire, Chief, Radiological Branch Chief Operating Officer Ohio Emergency Management Agency FirstEnergy Nuclear Operating Company 2855 West Dublin Granville Road Mail Stop A-GO-14 Columbus, OH 43235-2206 76 South Main Street Akron, OH 44308 Zack A. Clayton DERR David W. Jenkins, Attorney Ohio Environmental Protection Agency FirstEnergy Corporation P.O. Box 1049 Mail Stop A-GO-18 Columbus, OH 43266-0149 76 South Main Street Akron, OH 44308 State of Ohio Public Utilities Commission 180 East Broad Street Columbus, OH 43266-0573
Davis-Besse Nuclear Power Station, Unit 1 cc:
Danny L. Pace Senior Vice President, Fleet Engineering FirstEnergy Nuclear Operating Company Mail Stop A-GO-14 76 South Main Street Akron, OH 44308 Manager, Fleet Licensing FirstEnergy Nuclear Operating Company Mail Stop A-GHE-115 395 Ghent Road Akron, OH 44333 Director, Fleet Regulatory Affairs FirstEnergy Nuclear Operating Company Mail Stop A-GHE-315 395 Ghent Road Akron, OH 44333 Jeannie M. Rinckel Vice President, Fleet Oversight FirstEnergy Nuclear Operating Company Mail Stop A-GO-14 76 South Main Street Akron, OH 44308 Richard Anderson Vice President, Nuclear Support FirstEnergy Nuclear Operating Company Mail Stop A-GO-14 76 South Main Street Akron, OH 44308