ML070510609

Evaluation of 2005 Mid-Cycle (14MCO) Steam Generator Tube Inspections

ML070510609
Person / Time
Site:	Davis Besse
Issue date:	03/29/2007
From:	Thomas Wengert NRC/NRR/ADRO/DORL/LPLIII-2
To:	Bezilla M FirstEnergy Nuclear Operating Co
Wengert, Thomas
References
TAC MD0528
Download: ML070510609 (7)

Text

March 29, 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:

DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 - EVALUATION OF 2005 MID-CYCLE STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD0528)

Dear Mr. Bezilla:

By letters dated February 17, 2005, April 29, 2005, February 16, 2006, and October 22, 2006, you submitted information summarizing the results of the 2005 steam generator (SG) tube inspections performed at Davis-Besse Nuclear Power Station, Unit No. 1 (Davis-Besse). These inspections were performed during the cycle 14 mid-cycle outage (14MCO). In addition to these reports, the U.S. Nuclear Regulatory Commission (NRC) staff summarized additional information concerning the 2005 SG tube inspections at Davis-Besse in a letter dated September 1, 2005.

The NRC staff has completed its review of these reports and concludes that you have provided the information required by the Davis-Besse technical specifications and that no additional follow-up is required at this time. The NRC staffs review of the reports is enclosed.

Sincerely,

/RA/

Thomas J. Wengert, Project Manager Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-346

Enclosure:

Evaluation of Steam Generator Tube Inspection Reports cc w/encls: See next page

Mr. Mark B. Bezilla March 29, 2007 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:

DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 - EVALUATION OF 2005 MID-CYCLE STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD0528)

Dear Mr. Bezilla:

By letters dated February 17, 2005, April 29, 2005, February 16, 2006, and October 22, 2006, you submitted information summarizing the results of the 2005 steam generator (SG) tube inspections performed at Davis-Besse Nuclear Power Station, Unit No. 1 (Davis-Besse). These inspections were performed during the cycle 14 mid-cycle outage (14MCO). In addition to these reports, the U.S. Nuclear Regulatory Commission (NRC) staff summarized additional information concerning the 2005 SG tube inspections at Davis-Besse in a letter dated September 1, 2005.

The NRC staff has completed its review of these reports and concludes that you have provided the information required by the Davis-Besse technical specifications and that no additional follow-up is required at this time. The NRC staffs review of the reports is enclosed.

Sincerely,

/RA/

Thomas J. Wengert, Project Manager Plant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-346

Enclosure:

Evaluation of Steam Generator Tube Inspection Reports cc w/encls: See next page DISTRIBUTION:

PUBLIC LPL3-2 R/F RidsNrrPMTWengert RidsNrrDciCsgb RidsOgcRp RidsRgn3MailCenter RidsAcrsAcnwMailCenter DHills, RIII RidsNrrLAEWhitt RidsNrrDorlLpl3-2 KKarwoski, NRR ADAMS Accession Number: ML070510609 NRR-106 OFFICE PM/LPL3-2 LA/LPL3-2 DCI/CSGB/BC* BC/LPL3-2 NAME TWengert:mw EWhitt AHiser RGibbs DATE 3/28/07 3/28/07 3/22/07 3/29/07 OFFICIAL RECORD COPY

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

OFFICE OF NUCLEAR REACTOR REGULATION EVALUATION OF STEAM GENERATOR TUBE INSPECTION REPORTS FROM 2005 CYCLE 14 MID-CYCLE OUTAGE DAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1 DOCKET NO. 50-346

1.0 INTRODUCTION

By letters to the Nuclear Regulatory Commission (NRC) dated February 17, 2005 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML050530314),

April 29, 2005 (ADAMS Accession No. ML051230212), February 16, 2006 (ADAMS Accession No. ML060530594), and October 22, 2006 (ADAMS Accession No. ML062980206), FirstEnergy Nuclear Operating Company (FENOC), the licensee, submitted information summarizing the results of the 2005 steam generator (SG) tube inspections performed at Davis-Besse Nuclear Power Station, Unit No. 1 (Davis-Besse). These inspections were performed during the cycle 14 mid-cycle outage (14MCO). In addition to these reports, the NRC staff summarized additional information concerning the 2005 SG tube inspections at DBNPS in a letter dated September 1, 2005 (ADAMS Accession No. ML052310010).

2.0 BACKGROUND

Davis-Besse has two Babcock and Wilcox (B&W) once-through SGs. The tubes are sensitized Alloy 600 in the mill annealed condition. Prior to 14MCO, the last inspection of the SG tubes was completed on March 9, 2002. The NRC staff issued a license amendment on February 26, 2004 (ADAMS Accession No. ML040580026), regarding a one-time extension to the SG tube inservice inspection frequency. This amendment extended the 24-calendar month inspection frequency in Technical Specification (TS) Surveillance Requirement 4.4.5.3.a by approximately 12-calendar months. For most of the first 24-calendar months since the previous SG tube inspections, the plant was in an extended shutdown. As a result, the SGs were not exposed to the high temperature conditions generally required for corrosion-induced degradation of the SG tubes.

At the time of the mid-cycle inspection, the plant had operated for approximately 16.6 effective full power years. In the ?2A SG, there are 199 sleeves installed and in the ?1B SG, there are 212 sleeves installed. All sleeves were installed in the 1994-1996 timeframe in the lane/wedge region as a preventive measure against high-cycle fatigue. All sleeves are manufactured from Alloy 690 thermally-treated material. At the start of 14MCO, there were 32 tubes repaired by rolling in the ?2A SG and 8 tubes repaired by rolling in the ?1B SG. All of these re-roll repairs were performed in 2002.

Enclosure

3.0 RESULTS OF 2005 MID-CYCLE INSPECTION The licensee provided the scope, extent, methods, and results of their SG tube inspections in the documents referenced above. In addition, the licensee described corrective actions (i.e., 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:

During 14MCO, the licensee noticed that a shop re-roll (SRR) had been installed, during original manufacturing of the SGs, above the roll in the lower tubesheet in almost all the SG tubes (i.e., in all but 102 tubes). The tubes were re-rolled because the length of the original roll in the lower tubesheet was not controlled well and most were too short. The tubes were re-rolled prior to the annealing of the vessel. Based on the maintenance records, all of the tubes were supposed to have additional rolls installed. However, 102 did not have the SRR. The licensee indicated that 46 of the 102 tubes without a SRR contained rolls less than 1-inch in length. The shortest roll was 0.75 inches. The licensee indicated that, despite this condition, the tube would have been capable of performing its intended function (i.e., maintain structural and leakage integrity under a hot-leg large break loss of coolant accident (LBLOCA)) due to the presence of the seal weld. Axial indications were identified in the heel of the SRR in a total of 30 tubes in the

?1B SG. The licensee indicated the degradation was most likely caused by higher residual stresses in the SRR (i.e., higher than in the original roll). All of the tubes with axial indications in the area of the roll and SRR were plugged on detection. (The licensee initially attempted to install another re-roll above the original roll, or SRR, to enable them to leave the tube in-service. However, this process was not successful because there was tube springback due to the sludge and the roll wasnt acceptable.)

Approximately 34 tubes with a short original roll (and no SRR) were also plugged.

As a result of the above findings (i.e., the additional SRR), the licensee reviewed the manufacturing records for their SGs to identify any unknown design changes or construction features that could potentially impact the SG tubes. None were found.

No degradation was identified in dents, sleeves, or in the sludge pile region during this outage.

Intergranular attack and stress corrosion cracking (typically associated with grooves in the tubes) was identified in five tubes.

The internal auxiliary feedwater (AFW) headers were stabilized and functionally replaced by external headers in the 1980s. The repairs were qualified for postulated accident conditions. The internal AFW header and supporting welds are visually inspected each 10-year inservice inspection interval per TS 4.4.5.8. Inspections in 1990 and 1998 showed no evidence of movement or degradation of the AFW header or degradation of the AFW supply nozzles and thermal sleeves. During a visual inspection in 1998, one AFW nozzle was found to be stuck. As a result, the header at this nozzle location was inspected in 2000 and there was no evidence of movement or change in the header. The next 10-year inservice inspection interval at DBNPS begins in 2012, and the next visual inspection is scheduled for the 16th refueling outage. During each eddy current inspection, 100-percent of the periphery tubes are inspected with a bobbin coil, and an analysis is performed to ensure that the gap between the header and the

tubes is at least 0.250-inch. Although the inspections during 14MCO indicated that no AFW header movement had occurred, there was one small volumetric wear indication detected in the 2A SG in tube 146-50. This indication of wear was attributed to tube contact with the abandoned internal AFW header dowel pin support stay. As a result, it appears that the flow conditions in the 2A SG during the prior operating period were suitable to support some relative movement between the tube and the AFW header sufficient to cause contact with the support stay and initiate wear. A re-review of the 12th refueling outage eddy current data indicated there was some evidence that this indication was present during the 12th refueling outage. There have been no other similar indications observed in the SGs.

At the conclusion of the outage, there were 104 inservice tubes repaired by rolling in the

?2A SG and 8 tubes repaired by rolling in the ?1B SG.

A subsequent inspection of the SGs was performed in spring 2006.

4.0 CONCLUSION

S AND FUTURE INSPECTION PLANS Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by their TSs. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up action at this time since the inspections appear 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.

Note, however, that the NRC staff review did not address the acceptability of the licensees best-estimate, primary-to-secondary leakage expected for a LBLOCA. This best-estimate determination was performed to satisfy a license condition to permit the use of a re-roll repair process for the Davis-Besse SGs. The Babcock and Wilcox (B&W) plant licensees in the Pressurized Water Reactor Owners Group (PWROG) are addressing the LBLOCA of concern on a generic basis in a topical report that will be applicable to Davis-Besse. The NRC staff is currently reviewing that topical report which was submitted on January 4, 2007 (ADAMS Accession No. ML070330123). The NRC staff believes that the generic PWROG program is the proper place to address the LBLOCA issue since the technical nature of this issue is complex, and the issue is generic to B&W plants.

Principal Contributor: K. Karwoski Date: March 29, 2007