ML072740389

Review of Twelfth Refueling Outage Steam Generator Tube Inservice Inspection Report

ML072740389
Person / Time
Site:	Braidwood
Issue date:	10/17/2007
From:	Thorpe-Kavanaugh M M NRC/NRR/ADRO/DORL/LPLIII-2
To:	Crane C M Exelon Generation Co
Thorpe-Kavanaugh, Meghan, LPL3-1
References
TAC MD4199
Download: ML072740389 (5)

Text

October 17, 2007

Mr. Christopher M. Crane President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

BRAIDWOOD STATION, UNIT 2 - REVIEW OF TWELFTH REFUELING OUTAGE STEAM GENERATOR TUBE INSERVICE INSPECTION REPORT (TAC NO. MD4199)

Dear Mr. Crane:

By letter to the Nuclear Regulatory Commission (NRC) dated November 29, 2006 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML063130425), as supplemented by letters dated January 29, 2007 (ADAMS Accession No. ML070290637), and August 17, 2007 (ADAMS Accession No. ML072290564), Exelon Generation Company, LLC (the licensee), submitted information summarizing the results of the 2006 steam generator (SG) tube inspection activities at Braidwood Station, Unit 2, in accordance with Technical Specification (TS) Section 5.6.9, and as required by the American Society of Mechanical Engineers, Boiler and Pressure Vessel Code,Section XI. These inspections were performed during the twelfth refueling outage.

The NRC staff

=s review of the twelfth refueling outage SG tube inspection results is enclosed. The NRC staff concludes that the licensee provided the information required by the TSs, and that no additional follow-up is required at this time.

Sincerely, /RA/ Meghan M. Thorpe-Kavanaugh, Project Manager Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Docket No. STN 50-457

Enclosure:

Twelfth Refueling Outage SG Tube Inspection Results

cc w/encl: See next page

ML070290637), and August 17, 2007 (ADAMS Accession No. ML072290564), Exelon Generation Company, LLC (the licensee), submitted information summarizing the results of the 2006 steam generator (SG) tube inspection activities at Braidwood Station, Unit 2, in accordance with Technical Specification (TS) Section 5.6.9, and as required by the American Society of Mechanical Engineers, Boiler and Pressure Vessel Code,Section XI. These inspections were performed during the twelfth refueling outage.

The NRC staff

=s review of the twelfth refueling outage SG tube inspection results is enclosed. The NRC staff concludes that the licensee provided the information required by the TSs, and that no additional follow-up is required at this time.

Sincerely, /RA/ Meghan M. Thorpe-Kavanaugh, Project Manager Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Docket No. 50-457

Enclosure:

Twelfth Refueling Outage SG Tube Inspection Results

cc w/encl: See next page

DISTRIBUTION

PUBLIC RidsAcrsAcnwMailCenter LPL3-2 R/F RidsNrrDorlLpl3-2 RidsNrrPMMThorpe-Kavanaugh RidsOgcRp K.Karwoski, NRR RidsNrrDciCsgb RidsRgn3MailCenter

ADAMS: M072740389 *See memo ML072620310 OFFICE LPL3-2/PM LPL3-2/PM LPL3-2/LA DCI/CSGB/BC LPL3-2/BC

NAME MThorpe-Kavanaugh CGratton EWhitt AHiser* RGibbs DATE 10/11/07 10 / 05 /07 10/11/07 9 / 18 / 07 10/17/07 Enclosure

SUMMARY

OF THE NRC STAFF'S REVIEW REFUELING OUTAGE 12 STEAM GENERATOR TUBE INSERVICE INSPECTION REPORTS BRAIDWOOD STATION, UNIT 2 DOCKET NO. STN 50-457 By letter to the Nuclear Regulatory Commission (NRC) dated November 29, 2006 (Agency wide Documents Access and Management System (ADAMS) Accession No. ML063130425),

January 29, 2007, ADAMS Accession No. ML070290637), and August 17, 2007, ADAMS Accession No. ML072290564), Exelon Generation Company, LLC (the licensee), submitted information summarizing the results of the 2006 steam generator (SG) tube inspection activities at Braidwood Station, Unit 2. These inspections were performed during the twelfth refueling outage.

Braidwood Unit 2 has four Westinghouse Model D5 SGs, each containing 4,570 thermally treated Alloy 600 tubes. The tubes have an 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 in rows 1 through 9 was thermally stress relieved after bending.

The license provided the scope, extent, methods, and results of the SG tube inspections in the documents referenced above. In addition, the licensee described corrective actions (e.g., tube plugging) taken in response to the inspection findings.

As a result of the review of the reports, the NRC staff has the following comments/observations:

No tubes were identified that were not expanded for the full length of the tubesheet.

One tube was deplugged in 1991 (during the second refueling outage). A rotating probe inspection during the twelfth refueling outage (2006) of the region of the tube, where the plug had previously been installed, did not reveal any evidence of primary water stress corrosion cracking.

Several loose parts were identified during the outage and were not retrievable.

The licensee performed an analysis that determined operation until the next scheduled inspection (refueling outage thirteen), was acceptable with the loose parts remaining in the SGs.

Two tubes had indications slightly below a tube support plate. The indications were attributed to wear from a loose part. No loose part was evident in the eddy current data.

A visual inspection of this region could not be performed since the tubes are in the interior of the tube bundle. The tubes were plugged and stabilized.

Erosion of the moisture separator tangential nozzles, downcomer barrels, and swirl vanes were identified in SG D during the eleventh refueling outage inspections in 2005.

Follow-up visual inspections and ultrasonic thickness measurements were taken of the eroded areas in SG D during the twelfth refueling outage in 2006. The licensee's analysis indicated that the erosion in the affected areas was not projected to penetrate through-wall over the next operating cycle. The licensee plans to monitor the condition in order to develop degradation growth rates and take corrective actions if they become necessary. Inspections of these regions in the other steam generators are scheduled for 2008. Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by their technical specifications. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up action at this time, since the inspection appears to be consistent with the objective of detecting potential tube degradation, and the inspection results appear to be consistent with industry operating experience at similarly designed and operated units.

Principal Contributor: M. Abid, NRR

Date:

Braidwood Station, Units 1 and 2

cc: Document Control Desk - Licensing via e-mail

Mr. Dwain W. Alexander, Project Manager Westinghouse Electric Corporation via e-mail

Ms. Bridget Little Rorem Appleseed Coordinator via e-mail

Howard A. Learner Environmental Law and Policy Center of the Midwest via e-mail

Braidwood Senior Resident Inspector U.S. Nuclear Regulatory Commission via e-mail

Ms. Lorraine Creek RR 1, Box 182 Manteno, IL 60950

Illinois Emergency Management Agency Division of Disaster Assistance &

Preparedness via e-mail

County Executive via e-mail

Attorney General 500 S. Second Street Springfield, IL 62701

Plant Manager - Braidwood Station via e-mail

Site Vice President - Braidwood via e-mail

Senior Vice President - Operations Support via e-mail

Chairman, Ogle County Board Post Office Box 357 Oregon, IL 61061 Manager Regulatory Assurance - Braidwood via e-mail

Director - Licensing and Regulatory Affairs via e-mail

Associate General Counsel via e-mail

Senior Vice President - Midwest Operations via e-mail

Vice President - Regulatory Affairs via e-mail

Manager Licensing - Braidwood, Byron and LaSalle via e-mail