ML050470080
| ML050470080 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 02/23/2005 |
| From: | Dick G NRC/NRR/DLPM/LPD3 |
| To: | Crane C Exelon Generation Co |
| Dick G F, NRR/DLPM,415-3019 | |
| References | |
| TAC MC3737 | |
| Download: ML050470080 (6) | |
Text
February 23, 2005 Mr. Christopher M. Crane, President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
BYRON STATION, UNIT 2 - REVIEW OF STEAM GENERATOR INSPECTION REPORTS FROM THE SPRING 2004 REFUELING OUTAGE (TAC NO. MC3737)
Dear Mr. Crane:
By letters dated April 17, 2004 (ML041170314), June 23, 2004 (ML041830404), and November 10, 2004 (ML043210495), Exelon Generation Company, LLC (Exelon) submitted reports summarizing the steam generator (SG) inspections performed at Byron 2 during the 2004 refueling outage.
The NRC staff has reviewed the information submitted and concludes that Exelon provided the information required by their technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant followup action at this time since: (1) the inspections appear to be consistent with the objective of detecting potential tube degradation; and (2) with the exception of the degradation of the waterbox cap plate, which is addressed in the enclosed NRC staff evaluation, the inspection results appear to be consistent with industry operating experience at similarly designed and operated units.
Sincerely,
/RA/
George F. Dick, Sr. Project Manager Project Directorate III Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. STN 50-455
Enclosure:
As stated cc w/ encl: See next page
OFFICE OF NUCLEAR REACTOR REGULATION EVALUATION OF STEAM GENERATOR INSPECTION REPORTS FROM 2004 REFUELING OUTAGE BYRON STATION, UNIT 2 EXELON GENERATION COMPANY, LLC DOCKET NO. STN 50-455
1.0 INTRODUCTION
By letters dated April 17, 2004 (ML041170314), and June 23, 2004 (ML041830404), Exelon Generation Company, LLC (the licensee) submitted reports summarizing the steam generator (SG) inspections performed at Byron Station, Unit 2 (Byron 2) during their 2004 refueling outage. Additional information was provided in the licensee's letter of November 10, 2004 (ML043210495). NRC letter dated August 12, 2004 (ML042260202), documented a telephone call with the licensee held on April 9, 2004, to discuss immediate results of ongoing tube inspections and potential loose parts in the "A" SG as a result of degradation of the water box cap plate.
2.0 BACKGROUND
Byron 2 has four Westinghouse model D5 steam generators. Each SG contains 4,570 thermally treated Alloy 600 tubes. Each tube has a nominal outside diameter of 0.750-inch and a nominal wall thickness of 0.043-inch. The tubes were hydraulically expanded at both ends for the full length of the tubesheet and are supported by a number of stainless steel tube supports with quatrefoil shaped holes. The U-bend region of the tubes installed in rows 1 through 9 was thermally stress relieved after bending. The hot-leg temperature is 611 EF.
3.0 RESULTS FROM SG INSPECTIONS The licensee provided the scope, extent, methods, and results of their SG tube inspections in the documents referenced above. The licensee also described corrective actions (i.e., tube plugging or repair) taken in response to the inspection findings. There were several findings to note as a result of the review of the 2004 inspection reports:
A low frequency bobbin coil eddy current screening technique was used to identify tubes that may have an eddy current offset similar to that observed at Seabrook. At Seabrook, several tubes were identified to have crack-like indications associated with this offset (refer to NRC Information Notice 2002-21, "Axial Outside Diameter Cracking Affecting Thermally Treated Alloy 600 Steam Generator Tubing" dated June 25, 2002, and its Supplement dated April 1, 2003, for additional details). Of the 40 tubes identified with this offset, all were in higher-row tubes (i.e., greater than row 9). These tubes were inspected full length with a bobbin coil probe, and were inspected with a rotating probe at the hot-leg expansion transition region. No crack-like indications were found at any location during the steam generator tube inspections at Byron 2.
Degradation of the waterbox cap plate region of the "A" steam generator was observed during the outage. The waterbox is near the lower feedwater inlet and is associated with the preheater region of the steam generator. The cap plate (i.e., the top portion of the waterbox) was modified during initial steam generator fabrication to allow access to the waterbox. Additional information related to the degradation identified is contained in the NRC letter dated August 12, 2004 (ML042260202). As a result of the degradation of the waterbox cap plate region, the licensee evaluated the consequences of a failure of the cutout region and took corrective action as discussed in the August 12, 2004, letter. In summary, the licensee concluded that operation with the current condition of the waterbox was acceptable since if a failure of the cutout region were to occur, the results would be acceptable. The licensee plans to inspect this region during the next steam generator inspection and is developing a long-term strategy for addressing this issue. In addition, the licensee has trained (or is training) the operators on the expected plant response and operator actions if the cutout plate becomes loose.
4.0 CONCLUSION
S Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by the Byron technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant followup action at this time since:
(1) the inspections appear to be consistent with the objective of detecting potential tube degradation; and (2) with the exception of the degradation of the waterbox cap plate, which is addressed above, the inspection results appear to be consistent with industry operating experience at similarly designed and operated units.
Principal Contributor: K. Karwoski Date:
ML050470080 Nrr-106 OFFICE PM:PDIII-2 LA:PDIII-2 SC:PDIII-2 NAME GDick PCoates GSuh DATE 2/22/05 2/22/05 2/23/05 Byron Station Units 1 and 2 cc:
Regional Administrator, Region III U.S. Nuclear Regulatory Commission 801 Warrenville Road Lisle, IL 60532-4351 Illinois Emergency Management Agency Division of Disaster Assistance &
Preparedness 110 East Adams Street Springfield, IL 62701-1109 Document Control Desk - Licensing Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Mr. Dwain W. Alexander, Project Manager Westinghouse Electric Corporation Energy Systems Business Unit Post Office Box 355 Pittsburgh, PA 15230 Joseph Gallo Gallo & Ross 1025 Connecticut Ave., NW, Suite 1014 Washington, DC 20036 Howard A. Learner Environmental Law and Policy Center of the Midwest 35 East Wacker Drive Suite 1300 Chicago, IL 60601-2110 U.S. Nuclear Regulatory Commission Byron Resident Inspectors Office 4448 North German Church Road Byron, IL 61010-9750 Ms. Lorraine Creek RR 1, Box 182 Manteno, IL 60950 Chairman, Ogle County Board Post Office Box 357 Oregon, IL 61061 Mrs. Phillip B. Johnson 1907 Stratford Lane Rockford, IL 61107 Attorney General 500 S. Second Street Springfield, IL 62701 Byron Station Plant Manager Exelon Generation Company, LLC 4450 N. German Church Road Byron, IL 61010-9794 Site Vice President - Byron Exelon Generation Company, LLC 4450 N. German Church Road Byron, IL 61010-9794 Senior Vice President - Nuclear Services Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Vice President of Operations - Mid-West Pressurized Water Reactors Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Chairman Will County Board of Supervisors Will County Board Courthouse Joliet, Illinois 60434
Byron Station Units 1 and 2 Director - Licensing and Regulatory Affairs Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Regulatory Assurance Manager - Byron Exelon Generation Company, LLC 4450 N. German Church Road Byron, IL 61010-9794 Associate General Counsel Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Vice President -
Licensing and Regulatory Affairs Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555 Manager Licensing - Braidwood and Byron Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555