ML18024A058

Susquehanna Units 1 and 2 - Letter Attaching a Final Report of a Deficiency in Carriage Bolt Fasteners Used on 480 Volt Motor Control Center Bus Splices

ML18024A058
Person / Time
Site:	Susquehanna
Issue date:	09/18/1978
From:	Curtis N W Pennsylvania Power & Light Co
To:	Grier B H NRC Region 1
References
Download: ML18024A058 (12)

Text

0REGULATQRYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)DISTRIBUTIONFORINCOMINGMATERIAL-3388REC:GRIERBH,NRCORG:CURTISNWPAPWR5LIGHTDOCDATE:'09/i8/78DATERCVD:09/22/78DOCTYPE:LETTERNOTARIZED:NOCOPlESRECEIVED

SUBJECT:

LTRiENCLFORWARDINGFINALCONSTRUCTIONDEF1CIENCYREPTCONCERNINGDEFICIENCYINCARRIAGEBOLTFASTNERSUSEDON480VOLTMOTORCONTROLCENTERBUSSPLICES.PLANTNAME:SUSQUEHANNA'UNITiREVIEWERINITIAL:XJMSUSQUEHANNA-UNIT2DISTRIBUTERINITIAL~@~DITRIBUTIQNQFTHISMATERIALISASFOLLOWS+4~++++++++<<+++++NOTES:SENDISE3CYSFSAR5ALLAMDTSCONSTRUCTIONDEFICIENCYREPORT(iOCFR50.55E)(DlSTRIBUTIONCODEBOi9)FQRACTION:INTERNAL:EXTERNAL:ASSTDlRVASSALLO+4~W/ENCL~RGd&MINER~~W/ENCLREGFIL-/ENCLW/2ENCL'QSSICK0STAFF+4W/ENCLDIRECTORDPM4+W/ENCLQAB>>W/ENCLADFQRENG+4W/ENCLADFORPLANTSYSTEMS~~W/ENCLSTANDARDSDEV.<~W/ENCLFERDDREISER/IE+%W/ENCLLPDRSWILI<ESBARRE.F'A~~W/ENCLTERA~~W/ENCLNSIC~~~W/ENCLACRSCAT3>+W/ibENCLBRCIIIEFLWRN3BC<<W/ENCLLICASSTLWR03LA>+W/ENCLNRCPDR~>W/ENCLOELD44W/ENCLMIPC+~W/ENCLDEPUTYDIADPM~<W/ENCLDIRECTORDSS+4W/ENCLADFORREACSFTY+4W/ENCLADFORSYS8.PROJ>>W/ENCLl~SEYFRIT/IE44W/ENCLDISTRIBUTION:LTR41ENCL4iSIZE:2P+7P4%4%%%%4M%%%%%%%W-e$44443%%dF4&%%%%%%%%%CONTROLNBR:780860144AAlayTHEEND 1A TWONORTHNINTHSTREET,ALLENTOWN,PA.18101PHONE:(215)821-5151NORMANW.CURTISVicePresident.Engineering8Construction821-5381September18,1978Mr.BoyceH.GrierDirector,RegionIU.S.NuclearRegulatoryCatmission631ParkAvenueKLngofPrussia,Pennsylvania17406c>3~rl'k~raPlC/IPlrn~arrl'CQ7RmCAcn~CDSUSQU12iANNA,STE2%EL'ECTRICSTATIONFINALREPORTOFADEFICIEb~INCARRIAGEBOLTFASTEZKRSUSH3ON480VOLTMOTORCONTROLCEDERBUSSPLICESDOCK"TNOS:50-387/50-388LICENSENOS:CPPR-101/CPPR-102ERs100450/100508'ILE840-4'PTA-'290earMr.Grier:Attached'isaDefinitiveReportofthesubjectdeficiencyasreqLDxedby10CFR50.55(e).OnAugust8,1978,J.D.Green,PP&LResidentNuclearQualityAssuranceEngineer,advisedMr.R.Gallo,ReactorInspector,NRCRegionI,thatPP&Lwas2ntheprocessofevaluatingthergxz~bilityofthesubjectdeficiency.CoincidentwithPP&L'sverbaladvisorytotheCottmission,BechtelQualityAssuranceissuedYEAR-1-27(ManaganentCorrectiveActionReport)requestingthatBechtelProject.Engineeringmakeadeterminationregardingthereporta-bilityofthedeficiency.Thedetermination,affixtrtingthereportabilityofthedeficiency,wasmadeonAugust23,1978ardisthebasisfortheattachedfinalreport.The.defectivemater2alisbeingcontrolledandwillbecorrected.andclosedoutunder'heprovisionsofthe'echtelQualityProgram.Pleaseadviseshouldyourequireotherinformation.Verytrulyyours,N.W..CurtisVicePresident-Engineering&Construt~nARS.mcbAttachment7gOP+Oi44'ENNSYLVANIAPOWERILLIGHTCOMPANY Mr.BoyceH.GrierSeptenber18,1978ccrcMr.J.G.Davis(15)stingDirector-OfficeofInspection6EnforcementU.S.NuclearRegulatoryQmnissionWashington,D.C.20555Mr.G.McDonaM,Director(1)OfficeofManaganentInformation6ProgramControlU.S.NuclearRegulatoryCpu.ssionWashix~n,D.C.20555Mr.RobertM.GalloU.S.NuclearRegulatoryCaanissionP;O.Box52Shickshiany,Pennsylvaxua18655 FINALREPORTADEFICIENCYINCARRIAGEBOLTFASTENERSUSH3ON480VOLTMOXORC(MHDLCENTERTHESUSQUEHANNA.STEM1KZCTRICSTATIOND.P.ParsonsSSESElectricalGroupSupvr.CP,~c~~I07$A.M.e-SupervisingEngineer-Design-SuscpxehannaA.R.Manager-NuclearQualityAssurancePENNSYLVANIA,PONER&LIGHTCCMPANYALLENKNNgPENNSYLVANIASEPT1M3ER18,1978 CARRIAGEBOLTDEFICIENCYGH480VMYIQRCONXBDLCENZERBUSSPLICES-P.O.8856-E-118ACSUSQUl5iANNA.STEAMEf.ECTRICSTATIONUNITS1&2 TABLEOFCONTENTSIntroductionDescriptionoftheDeficiencyAnalysisofSafetyImplicationsCorrectiveActionConclusionsPg.1Pgs.1,.2Pgs~2g3Pgse3g4Pg.4 ThisreportispresentedinaccordancewiththerequirenentsofTitle10,CodeofFederalRegulationsgPart50'ection50.55(e).AdeficiencyinecpignentsuppliedbyCutler-Hanrner,Inc.wasdiscovered,duringconstructionactivitiesbeingperformedattheSuscpehannaSteamElectricStation(SSES).PP&L'sA/instructor(Bechte1)ginthecourseofinstallingcarriageboltswhichareusedtosplicebussectionsattheshippingsplitsof480voltnntorcontrolcenterunits,notedtheoccurrenceofseveralcasesofthreadfai1ures(strippedthreads)whiletorcpiagthebolts.Thefailuresandtheircausewereassessedfartheirimpactonthesafetyof~'perationoftheplant.Baseduponanevaluationofthesafetyimplications,BechtelEngineeringhasconcludedthattheconditionisreportableunder10CFR50.55(e)because,wereittohaveremaineduncorrected,theconditioncouldhaveadverseaffectsonthesafeoperationoftheplant.DEK5GPTIONGFTHEDEFICIENCYThedesignofSuscpehannaUnits1a2providesfor28safetyrelated.480Vabatorcontrolcenters.Duringtheinstallationofthese480Vmntorcontrolcentersections,itwasnotedthatthe3/8"carriageboltssuppliedfor I~efasteningthe480Vbusspliceplateswereexperiencingrandomthreadfailureswhentorquedtoappxmxnately18ft./lbs.1Investigationoftheseboltfailuresrevealedthefollowingfacts:l.The3/8"diametercarriageboltssuppliedhyCutler-Hztaerforuseinthe480Vbussplicesweresuppliedasamixedpacketwith1/4"thickand.3/8"thicknuts.2.TheinstructionmanualfurnishedbyCutler-Hamaerfortheinstallationofthe480VMX'sdidnotspecifythepropercanbinationoffastenerstobeusedforthebussplices;therebypermitting3/8"carriageboltstobematedwith1/4"or3/8"thicknuts.Inadd.tiOn,,theinstructionmanualdidnotprovidevaluesfortoxquingthe3/8"carriagebolts.3.Alloftheholtthreadfailureswhichweredetectedoccurredwhena1/4"thicknutwasuti1izedincanbinationwitha3/8"diametercarriagebolt.Cutler-Hanaierwasapprisedoftheaboveinformation,andtheyadvisedthatthecorrectsplicefastenerwasa3/8"carriageboltwithafull3/8"thicknuttorchedto18ft./lbs.ThecarriageboltthreaRfailurehasbeendetatzninedtohavebeencausedbytheundersized(1/4"thick)"jam"nuts.MALYSISOFSM.f"TYIMPLICATIONSThe480VmotorcontrolsystandesignwasreviewedandthefollawLingwasconcludedfortheworstcondition,includingapostulatedseismicevent:Thedeficiency,whichinvolvesthe.actualstrippingofthreadsonsomeofthecarriagebolts,isconcealedbywashersandthenutsusedtofastenthebolts.Ifundetected,oruncorrected,thisconditioncouldpermittingsurfaces,ofthebusandthebusspliceplatestobelooselyjoinedatapointwhichwasdesignedtoc;cry600amperesofloadcurrent.

Underload,suchlooseconnectionscoulddeveloparcingandoverheatingwhichcouldresultinafireorbusfai1ureandthelossoftheactorcontrolcenter.Inthosecaseswhereactualthreadstrippirxyhadnotocnowed,theundersizednutsmayhave,nonetheless,causedsufficientoverstressonthecarriageboltsthatanincipientfailureofthethreadscouldexist.Mdedforcesfranaseismiceventcouldcauseoverstressed.boltstofail,looseningthebusjoint.Sucheventscouldresultinthesituationdescribedinthepreceedingparagraph.Sincethreadstrippingorincipientthreadstrippingofthesecarriageboltsisarareeventandcouldoccurinanyora11ofthesafeguaxds~torcontxolcenters,thepossibilityofacaravanmodefai1ureexists.The.simultaneouslossofredundantmotorcontrolcenterfeeds,whichservevitalsafetyrelatedloads,couldresultinasafetyhazardtotheoperationoftheplant.CORRECTIVEACTIONTAKERTOCGFIRQLTHEDEFICIENTITEMBechtelQualityContxolissuedNonconformanceReportN'o.2855on8/2/78toidentifyandcontxolthe480VYdX."s(twenty)present1yonsiteforthecarriageboltdeficiencybeingreported.BechtelQKgeneratedManaganentCorrectiveActionRequestNo.1-27datedAugust.7,1978inordertoobtaindocumentedevidenceofBechte1Project Engineering'sevaluationofthecauseofthecondition,thecorrectiveactionrequired,andthecondition'sr@artabilityunder10CPR50.55(e).CORRECTIVEACTIONKORESOLVETHEDEFICIENCYCuttler-HamoerwillreplaceallcarriageboltsandnutsusedforsplicinglinksatshippingsplitsonMCCswith3/8"boltsand3/8"thicknessnutsforallMCCsalreadyinstalled,wil1replace1/4"nutswithfull-nuts(3/8")forKCsthatarenotyetinstalled,andwillutilized3/8"thicknutsforMZscurrent1ybeingmanufactured.(Thiswasdocumentedina~franCutler-HanaertoBechteldated8/28/78.)Cutler-Hamnerhasupdatedthe480VIKCinstructionbooktoixmludetherecpiredtorquevalues(18ft./lbs.)andhastransmittedarevisedinstructionmanualtotheBechtelfieldforces.~CONCLUSIONSWiththereplacementofall3/8"carriageboltsandnutsonallthebussplicesofallmotorcontrolcentersalreadydeliveredtotheSSESsitewithcorrect3/8"boltsand3/8"thicknuts,withthecorrecttorquingofthesefastenersto18ft.lbs.,andwithallfuturemotorcontxolcentersbeingsuppliedwithcorrecthardware,therequirementsofSpecification8856-E-118Revision6,Paragraph9.2.1willhavebeenmet;thedeficiencywillhavebeencorrected;andthepotentialsafetyhazardwi11havebeene1iminated.TheBechtelgeneratedNonconformanceReport(NCRNo.2855)willnotbecloseduntilthereisQualityControlverificationthatthe480VMCCsbusspliceshavebeencompletedinaccordancewiththedesignandvendorrequirementsandtheatterx3antinspectionshavebeenacccmplished.