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, 2007Mr. Mark B. BezillaSite 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 OF2005 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 providedthe information required by the Davis-Besse technical specifications and that no additional follow-up is required at this time. The NRC staff's review of the reports is enclosed.Sincerely,/RA/Thomas J. Wengert, Project ManagerPlant Licensing Branch III-2 Division of Operating Reactor Licensing Office of Nuclear Reactor RegulationDocket No. 50-346

Enclosure:

Evaluation of Steam Generator Tube Inspection Reportscc w/encls: See next page Mr. Mark B. BezillaMarch 29, 2007Site 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 OF2005 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 providedthe information required by the Davis-Besse technical specifications and that no additional follow-up is required at this time. The NRC staff's 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 RegulationDocket No. 50-346

Enclosure:

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

PUBLICLPL3-2 R/FRidsNrrPMTWengert RidsNrrDciCsgbRidsOgcRpRidsRgn3MailCenter RidsAcrsAcnwMailCenterDHills, RIIIRidsNrrLAEWhitt RidsNrrDorlLpl3-2KKarwoski, NRRADAMS Accession Number: ML070510609NRR-106OFFICEPM/LPL3-2LA/LPL3-2DCI/CSGB/BC*BC/LPL3-2 NAMETWengert:mwEWhittAHiserRGibbsDATE3/28/07 3/28/07 3/22/07 3/29/07OFFICIAL RECORD COPY Davis-Besse Nuclear Power Station, Unit 1 cc:Manager, Site Regulatory ComplianceFirstEnergy Nuclear Operating CompanyDavis-Besse Nuclear Power StationMail Stop A-DB-30655501 North State Route 2Oak Harbor, OH 43449-9760Director, Ohio Department of CommerceDivision of Industrial ComplianceBureau of Operations & Maintenance6606 Tussing RoadP.O. Box 4009Reynoldsburg, OH 43068-9009Regional Administrator, Region IIIU.S. Nuclear Regulatory CommissionSuite 2102443 Warrenville RoadLisle, IL 60532-4352Resident InspectorU.S. Nuclear Regulatory Commission5503 North State Route 2Oak Harbor, OH 43449-9760Stephen HelmerSupervisor, Technical Support SectionBureau of Radiation ProtectionOhio Department of Health35 East Chestnut Street, 7 th FloorColumbus, OH 43215Carol O'Claire, Chief, Radiological BranchOhio Emergency Management Agency2855 West Dublin Granville RoadColumbus, OH 43235-2206Zack A. Clayton DERROhio Environmental Protection AgencyP.O. Box 1049Columbus, OH 43266-0149State of OhioPublic Utilities Commission180 East Broad StreetColumbus, OH 43266-0573Attorney General Office of Attorney General30 East Broad StreetColumbus, OH 43216President, Board of CountyCommissioners of Ottawa CountyPort Clinton, OH 43252 President, Board of CountyCommissioners of Lucas CountyOne Government Center, Suite 800Toledo, OH 43604-6506The Honorable Dennis J. KucinichUnited States House of RepresentativesWashington, D.C. 20515The Honorable Dennis J. Kucinich United States House of Representatives14400 Detroit AvenueLakewood, OH 44107 Gary R. LeidichPresident and Chief Nuclear OfficerFirstEnergy Nuclear Operating CompanyMail Stop A-GO-1976 South Main StreetAkron, OH 44308Joseph J. HaganSenior Vice President of Operations and Chief Operating OfficerFirstEnergy Nuclear Operating CompanyMail Stop A-GO-1476 South Main StreetAkron, OH 44308David W. Jenkins, AttorneyFirstEnergy CorporationMail Stop A-GO-1876 South Main StreetAkron, OH 44308 Davis-Besse Nuclear Power Station, Unit 1 cc:

Danny L. PaceSenior Vice President, Fleet EngineeringFirstEnergy Nuclear Operating CompanyMail Stop A-GO-1476 South Main StreetAkron, OH 44308Manager, Fleet LicensingFirstEnergy Nuclear Operating CompanyMail Stop A-GHE-115395 Ghent RoadAkron, OH 44333Director, Fleet Regulatory AffairsFirstEnergy Nuclear Operating CompanyMail Stop A-GHE-315395 Ghent RoadAkron, OH 44333Jeannie M. RinckelVice President, Fleet OversightFirstEnergy Nuclear Operating CompanyMail Stop A-GO-1476 South Main StreetAkron, OH 44308Richard AndersonVice President, Nuclear SupportFirstEnergy Nuclear Operating CompanyMail Stop A-GO-1476 South Main StreetAkron, OH 44308 EnclosureOFFICE OF NUCLEAR REACTOR REGULATIONEVALUATION OF STEAM GENERATOR TUBE INSPECTION REPORTSFROM 2005 CYCLE 14 MID-CYCLE OUTAGEDAVIS-BESSE NUCLEAR POWER STATION, UNIT NO. 1DOCKET NO. 50-34

61.0INTRODUCTION

By letters to the Nuclear Regulatory Commission (NRC) dated February 17, 2005 (AgencywideDocuments Access and Management System (ADAMS) Accession No. ML050530314),April 29, 2005 (ADAMS Accession No. ML051230212), February 16, 2006 (ADAMS AccessionNo. ML060530594), and October 22, 2006 (ADAMS Accession No. ML062980206), FirstEnergyNuclear Operating Company (FENOC), the licensee, submitted information summarizing theresults of the 2005 steam generator (SG) tube inspections performed at Davis-Besse NuclearPower Station, Unit No. 1 (Davis-Besse). These inspections were performed during the cycle14 mid-cycle outage (14MCO). In addition to these reports, the NRC staff summarizedadditional information concerning the 2005 SG tube inspections at DBNPS in a letter datedSeptember 1, 2005 (ADAMS Accession No. ML052310010).

2.0BACKGROUND

Davis-Besse has two Babcock and Wilcox (B&W) once-through SGs. The tubes are sensitizedAlloy 600 in the mill annealed condition. Prior to 14MCO, the last inspection of the SG tubeswas 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 tubeinservice inspection frequency. This amendment extended the 24-calendar month inspectionfrequency in Technical Specification (TS) Surveillance Requirement 4.4.5.3.a by approximately12-calendar months. For most of the first 24-calendar months since the previous SG tubeinspections, the plant was in an extended shutdown. As a result, the SGs were not exposed tothe high temperature conditions generally required for corrosion-induced degradation of the SGtubes.At the time of the mid-cycle inspection, the plant had operated for approximately 16.6 effectivefull power years. In the

?2A" SG, there are 199 sleeves installed and in the

?1B" SG, there are212 sleeves installed. All sleeves were installed in the 1994-1996 timeframe in the lane/wedgeregion as a preventive measure against high-cycle fatigue. All sleeves are manufactured fromAlloy 690 thermally-treated material. At the start of 14MCO, there were 32 tubes repaired byrolling in the

?2A" SG and 8 tubes repaired by rolling in the

?1B" SG. All of these re-roll repairswere performed in 2002. 3.0RESULTS OF 2005 MID-CYCLE INSPECTIONThe licensee provided the scope, extent, methods, and results of their SG tube inspections inthe 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, duringoriginal manufacturing of the SGs, above the roll in the lower tubesheet in almost all theSG tubes (i.e., in all but 102 tubes). The tubes were re-rolled because the length of theoriginal roll in the lower tubesheet was not controlled well and most were too short. Thetubes were re-rolled prior to the annealing of the vessel. Based on the maintenancerecords, all of the tubes were supposed to have additional rolls installed. However, 102did not have the SRR. The licensee indicated that 46 of the 102 tubes without a SRRcontained rolls less than 1-inch in length. The shortest roll was 0.75 inches. Thelicensee indicated that, despite this condition, the tube would have been capable ofperforming its intended function (i.e., maintain structural and leakage integrity under ahot-leg large break loss of coolant accident (LBLOCA)) due to the presence of the sealweld. 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 higherresidual stresses in the SRR (i.e., higher than in the original roll). All of the tubes withaxial indications in the area of the roll and SRR were plugged on detection. (Thelicensee initially attempted to install another re-roll above the original roll, or SRR, toenable them to leave the tube in-service. However, this process was not successfulbecause there was tube springback due to the sludge and the roll wasn't 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 themanufacturing records for their SGs to identify any unknown design changes orconstruction 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 thisoutage.Intergranular attack and stress corrosion cracking (typically associated with grooves inthe tubes) was identified in five tubes.The internal auxiliary feedwater (AFW) headers were stabilized and functionallyreplaced by external headers in the 1980s. The repairs were qualified for postulatedaccident conditions. The internal AFW header and supporting welds are visuallyinspected each 10-year inservice inspection interval per TS 4.4.5.8. Inspections in 1990and 1998 showed no evidence of movement or degradation of the AFW header ordegradation of the AFW supply nozzles and thermal sleeves. During a visual inspectionin 1998, one AFW nozzle was found to be stuck. As a result, the header at this nozzlelocation was inspected in 2000 and there was no evidence of movement or change inthe header. The next 10-year inservice inspection interval at DBNPS begins in 2012,and the next visual inspection is scheduled for the 16 th refueling outage. During eacheddy current inspection, 100-percent of the periphery tubes are inspected with a bobbincoil, 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 noAFW header movement had occurred, there was one small volumetric wear indicationdetected in the "2A" SG in tube 146-50. This indication of wear was attributed to tubecontact with the abandoned internal AFW header dowel pin support stay. As a result, itappears 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 headersufficient to cause contact with the support stay and initiate wear. A re-review of the 12 threfueling outage eddy current data indicated there was some evidence that this indication was present during the 12 th refueling outage. There have been no othersimilar 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.

4.0CONCLUSION

S AND FUTURE INSPECTION PLANSBased on a review of the information provided, the NRC staff concludes that the licenseeprovided the information required by their TSs. In addition, the NRC staff concludes that thereare no technical issues that warrant follow-up action at this time since the inspections appear tobe consistent with the objective of detecting potential tube degradation and the inspectionresults appear to be consistent with industry operating experience at similarly designed andoperated units. Note, however, that the NRC staff review did not address the acceptability of the licensee'sbest-estimate, primary-to-secondary leakage expected for a LBLOCA. This best-estimatedetermination was performed to satisfy a license condition to permit the use of a re-roll repairprocess for the Davis-Besse SGs. The Babcock and Wilcox (B&W) plant licensees in thePressurized Water Reactor Owner's Group (PWROG) are addressing the LBLOCA of concernon a generic basis in a topical report that will be applicable to Davis-Besse. The NRC staff iscurrently reviewing that topical report which was submitted on January 4, 2007 (ADAMSAccession No. ML070330123). The NRC staff believes that the generic PWROG program isthe proper place to address the LBLOCA issue since the technical nature of this issue iscomplex, and the issue is generic to B&W plants.Principal Contributor: K. Karwoski Date: March 29, 2007