ML071300649
| ML071300649 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 05/16/2007 |
| From: | Catherine Haney Plant Licensing Branch III-2 |
| To: | Wadley M Nuclear Management Co |
| chawla M, ADRO/DORL, 415-8371 | |
| References | |
| TAC MD4174 | |
| Download: ML071300649 (4) | |
Text
May 16, 2007 Mr. Michael D. Wadley Site Vice President Prairie Island Nuclear Generating Plant Nuclear Management Company, LLC 1717 Wakonade Drive East Welch, MN 55089
SUBJECT:
PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNIT 1 - PRESSURIZER SURGE, SPRAY, SAFETY, AND RELIEF NOZZLE WELD SUSCEPTIBILITY TO PRIMARY WATER STRESS-CORROSION CRACKING (TAC NO. MD4174)
Dear Mr. Wadley:
This letter acknowledges the receipt of information from Nuclear Management Company, LLC pertaining to the pressurizer surge, spray, safety, relief nozzle, and safe-end welds at Prairie Island Nuclear Generating Plant, Unit 1.
The discovery, in October 2006, of five circumferential indications in three Alloy 82/182 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.
Based on discussions with the NRC staff, licensees of plants susceptible to this condition have committed to enhanced inspection frequency and reactor coolant system leakage monitoring until actions to mitigate the potential of PWSCC in the affected welds have been completed.
M. D. Wadley In your letter dated January 30, 2007 (Agencywide Documents Access & Management System (ADAMS) Accession No. ML070310270), you stated that the pressurizer at Prairie Island Nuclear Generating Plant, Unit 1, does not have Alloy 82/182 butt welds. As a result, your response adequately addresses the concerns that the NRC has at this time regarding PWSCC susceptibility of these welds.
Sincerely, Timothy J. McGinty /RA/ For Catherine Haney, Director Division of Operating Reactor Licensing Office Of Nuclear Reactor Regulation Docket No. 50-282 License No. DPR-42 cc: See next page
ML071300649 OFFICE CPNB LPL3-1/PM LPL3-1/LA NAME TLupold MChawla THarris DATE 5/16/07 5/14/07 5/11/07 OFFICE LPL3-1/BC CPNB/BC DORL/D NAME L Raghavan TChan CHaney DATE 5/16/07 5/10/07 5/16/07
Prairie Island Nuclear Generating Plant, Units 1 and 2 cc:
Jonathan Rogoff, Esquire Vice President, Counsel & Secretary Nuclear Management Company, LLC 700 First Street Hudson, WI 54016 Manager, Regulatory Affairs Prairie Island Nuclear Generating Plant Nuclear Management Company, LLC 1717 Wakonade Drive East Welch, MN 55089 Manager - Environmental Protection Division Minnesota Attorney Generals Office 445 Minnesota St., Suite 900 St. Paul, MN 55101-2127 U.S. Nuclear Regulatory Commission Resident Inspector's Office 1719 Wakonade Drive East Welch, MN 55089-9642 Regional Administrator, Region III U.S. Nuclear Regulatory Commission Suite 210 2443 Warrenville Road Lisle, IL 60532-4351 Administrator Goodhue County Courthouse Box 408 Red Wing, MN 55066-0408 Commissioner Minnesota Department of Commerce 85 7th Place East, Suite 500 St. Paul, MN 55101-2198 Tribal Council Prairie Island Indian Community ATTN: Environmental Department 5636 Sturgeon Lake Road Welch, MN 55089 Nuclear Asset Manager Xcel Energy, Inc.
414 Nicollet Mall, R.S. 8 Minneapolis, MN 55401 Michael B. Sellman President and Chief Executive Officer Nuclear Management Company, LLC 700 First Street Hudson, MI 54016 Douglas E. Cooper Senior Vice President and Chief Nuclear Officer Nuclear Management Company, LLC 700 First Street Hudson, WI 54016 July 2006