ML18024A114

Susquehanna Units 1 and 2 - a Reaction to Cracking of Austenitic Stainless Steel Piping in Boiling Water Reactors (Includes Susquehanna Ses Design Modifications)

ML18024A114
Person / Time
Site:	Susquehanna
Issue date:	01/24/2018
From:	Mead E M Pennsylvania Power & Light Co
To:	Office of Nuclear Reactor Regulation
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PENNSYLVANIAPOWER8cLIGHTCCMPANYAREACTIONK)CRACKINGOFAUSTENITICSTAINLESSS9ZELPIPINGINBOILINGWATERREACTORS(INCLUDESSUSQUEHANNASESDESIGNMODIFICATIONS)EarleM.Mead./ProgectEngineeringManagerSusquehannaSES TableofContentsl.Introduction2.ProblemStatementSafetySignificancePrimaryConsiderations4.1Environmental(CoolantChemistry)4.2Stress4.3Material5SusquehannaSESPreventiveMeasures5.1Environment5.1.1ChemicalControl5.1.2MechanicalControl5.1.2.1ControlRodDrive(CRD)PumpSuctionRelocation5.1.2.2MechanicalVacuumDeaeration5.1.3OperatingProcedures5.2Stress5.2.1'DesignStresses5.2.2FabricationStresses5.2.2.1Fit-up5.2.2.2InitialFabrication(Shop)5'2.2.3Welding-Induced.Stress5.2.2.3.1HeatInput5.2.2.3.2JointDesign5.2.2.3.3FillerMetal5.2.2.3.4Cleanliness TableofContentsPage5.2.3'ethodsofStressReduction105.2.3.1SolutionHeatTreatment5.2.3.2HeatSinkMelding5.2.3.3InductionHeatingStressImprovement105.3Material5~3-1503~2CoreSpraySystemReactorRecirculationSystemDischargeGateValveBypassLine13135~3~353~.6.ReferencesControlRodDriveReturnLineRecirculationRiserpipes1315 TableandIllustrationTable1Figure1

~~'1.IntroductionThisreportoriginallyresultedfromaninformalteleconbetweenrepresentativesofPPM.andtheNRCwhichoccurredinFebruary1976.AtthattimeproposedSusquehannaSteamElectricStation(SSES)designchangeswerebrieflydiscussedanditwasagreedthatthisadditionalinformationshould.besubmitted.,SubsequenttotheoriginalissueofthisreporttherehavebeennumerousincidentsattributedtoIntergranularStressCorrosion.Cracking(IGSCC).Based.ontheseincidents,PPM,hasmodifiedourpositiononIGSCC,whichincludedadditionaldesignchangesatSSES..FortheabovereasonandtoprovidetheNRCwithPAL'spositiononNUHEG-0313,thisreporthasbeenrevisedandupdated.

2.ProblemStatementFromSeptember,1974toOctober,1976crackinghad.beendiscovered.inrecirculationbypassloops,corespraylinesand.controlrod.drivereturnlinesof10GEboilingwaterreactors.Theaffectedunitswere:a)Corespraylines-Dresden2,Fukushima1,and.Tsurugab)Recirculationbypasslines-Dresden2,QuadCities1,QuadCities2,PeachBottom3,MillstonePoint1,Monticello1,Fukushima1,Hamaoka1,Brunswick2,Hatch1,and.Pilgriml.c)Contxolroddrivereturnlines-TarapurPP8cLbelievedthatsufficientJustificationexisted.torecognizethecauseasbeingIntergranularStressCorrosionCracking.ThisreportwasoriginallyissuedonOctober12,1976and.summarizedPP8cL'sconcernsaswellasmodificationsthatwereimplementedforSSES.FromOctober1976tothepresenttherehavebeen'numerousreportsofcrackingatotherplantswhichhasbeenattributedtoIGSCC.Notonlyhavetheabovelinesbeenaffected,buttherearereportsofcrackinginheadventlines,recirculationriserlines,instrumentlines,andalso,mainrecirculationandfeedwaterlines.ThisreporthasbeenrevisedtoreflectPPM'spositiononIGSCCand.thelatestmodificationswhichhavebeenmadeatSSES.

3.SafetySignificancePPM,considersthestatementinNUREG-0313,whichreadsinpart,"Althoughtheprobabilityisextremelylowthatthesestresscorrosioncrackswillpropagatefarenoughtocreateasignificantsafetyhazardtothepublic,thepresenceofsuchcracksisundesirable"tobeanaccurateassessmentofthesafetysignificance.Beyond,thatPPMbelievesthesignificanceofthefailurestorelateonlytoplantreliability.Based,onpreviousBWRexperience,itcanbeexpected.thatbrittlecrackingwillnotoccurinausteniticType304stainlesssteeland.thatsmallleakswillbedetected,v5.suallyand/orbyleakdetectioninstrumentationiftheyoccurinsidetheprimarycontainment.Theimportanceofdetectabilityhasbeenrecognized,andtheSSESdrywellleakdetectionsystemwillcomp~withNRCRegulatoryGuide1.45(May1973).TheInserviceInspectionProgramatSSESisinaccordancewiththerequirementsoftheASMEBoilerandPressureVesselCode,SectionXI,"RulesforInserviceInspectionofNuclearPowerPlantComponents",1974edition,includingaddendathroughSummer1975,asmodified.byAppendixIIItoMinter1975addenda,"UltrasonicExaminationMethod.forClass1andClass2PipingSystemsMadefromFerriticSteels",andINA-2232ofthe,Summer1976Addenda,using50+pofthereferencelevelascriteriaforinvestigatingreflectors.TheISIProgramwillbeupdated,asrequired/allowedby10CFR50.55a(g).ItwillalsobeaugmentedtocomplywiththerecommendationsofNUREG-0313.ThedegreeofaugmentationwilldependontheoutcomeofPPM,'sdetailedevaluationofIGSCCatSSES.Thisevaluationwillbecompleted.byJanuary1,1990and.willaddressallapplicablelineswhichcontainreactorcoolant.Itwilldelineateallmaterialsandanyfabricationprocesseswhichwillprovideacomprehensivelisting'ofsusceptiblelinesintheasinstalledcondition.ThestudywillthenprovideanevaluationofallIGSCCcountermeasureswhichareavailableforuseatSSES.Theconclusionofthestudywillbearecommendationofwhat"courseofaction"shouldbetakenforeachsusceptibleline>fromwhichcountermeasuresshould.beusedtohowtheISIProgramshould.beaugmented..

4'r1maryConsiderations4.1Environment(CoolantChemi,stry)ThecoolantchemistryinBoilingWaterReactorsisestablished.primarilytoensurecompat1bilitywithmaterialsusedthroughouttheNuclearSteamSupplySystem.Hence,neutral,high-puritywaterisusedand.halogensarestringentlylimited..Limitationsarealsoplacedonthesilicaand.copperconcentrationstopreventtheirdepositionintheturbine.Dissolved.oxygenconcentrationisnotnormallycontrolledbychemicaladditionormechanicaldeaeration.Withoutchemicalormechanicalcontrolthesteadystatelevelofdissolved.oxygenatSSESduringnormaloperationwillbeamaximumof7.1ppb.However,duringlowloadornoload.cond1tionstheoxygenconcentrationcanapproachsaturationwhich,underconditionsofstandardtemperatureandpressure,is8.0ppm.Underthecombinedinfluencesofsensitizationandhightensilestressthisoxygenlevelismorethansufficienttoenablestresscorrosioncrackingofausteniticstainlesssteeltooccur.Since,forconstantvaluesofsensitizationand.stress,tim-to-failure1sd.irectlyproportionaltodissolved.oxygenconcentration,lowflowandstagnantlinesarehigh+suspect.Itwould.,therefore,beverybeneficialtoreducetheoxygenleveltoaslowaspossibledur1ngallphasesofplantoperat1on.4.2StressThedesignstresslevelsforNuclearSteamSupp+System(NSSS)pipingareestablished.withintheconstraintsoftheAQSCodeaswellasanyloadingrestrictionswhichmightbeimposed.bytheNSSSvendor.StresslevelssufficienttoresultinIGSCCgenerallyarenot'usttheresultofordinarily-appliedengineeringloadsorstresses.Rather,theyresultfromthecombind'ffectsofallsourcesofstressand.strain:i.e.,residuals,thermal,surface,service,etc.IItisverybeneficialtomin1mizetheamountofstressactingonthesens1tized.material.Therefore,theamountofresidualand.applied.stressesshouldbereducedwhereverpossible.4.3NaterialBoilingWaterReactorpipingisfabricatedfromsteelswhichare:corrosionresistant,tough,stabledimnsional+,sufficientlystrongforanticipatedloadings,resistanttoradiat1ondamage,resistanttobothacidicandbasicchemicalattack,economical,and.anticipated.tobeavailableintheforeseeablefuture.Themostprominentmaterialsused.areausteniticstainlesssteels(Types304and,316)and,carbonsteel.

"l However,ithasbeendeterminedthatthestandardgradesof304and.316stainlesssteelwithhighcarboncontentsofapproximately.06to.08percentarethegradeswhichproducethemostseveresensitizationand.thus,thegreatestsusceptibilitytoIGSCC.Thelowcarbon((.03percentcarbon)gradesof304and316stainlesssteelaredemonstratingamuchgreaterresistancetoIGSCC.Theseand,otheralternatematerialsareundergoingextensivedevelopmentand,evaluationforreducingtheprobabilityofIGSCC.

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5.SSESPreventiveMeasuresPP&LeffortshavecenteredonreducingtheprobabilityofoccurrenceofIGSCCforSSES.RecommendedmodificationstotheexistingSSESdesignwereevaluated,priortoimplementationagainstthefallowingcriteria:1.TheirpotentialforsubstantiallyreducingtheprobabilitythatXGSCCwilloccur;2.Theirpotentialforsubstantiallyreducingthetimerequired.todetectcracksorleaksresultingfromXGSCC;3.Theirpotentialforcreatingotherproblemswhichwouldeitherbeasbad.as,orworsethan,thecurrentproblem.5.1EnvironmentCurrent'nalysesindicatethatamongtheenvironmentrelated.contributorstothecurrentZGSCCprobleminBWR's,thedissolvedoxygenconcentrationofthereactorcoolantisprobablythemostsignificant.Oxygenlevelscanbecontrolled,eitherchemically,mechanically,oroperationally.5.1.1ChemicalControlSincethereisnouniversalinhibitor'forimprovingBMRwaterchemistryand.sincetherearelimited.dataconcerningtheuseofoxygenscavengersandneutralizersinBNR's,theiruseintheprimarycoolantisnotconsidered.atthistime.Futuredevelopmentsinthisarea,however,willbefallowed..5.1.2MechanicalControlPrimaryoxygenremovalisaccomplishedinthecondenserduringnormaloperation.Duringthisphasetheoxygenlevelismaintained.atapproximately'$.0ppb.Duringanycombinationofpartialload.(startup,shutdown,hotstandbyandsomeabnormalevents)theoxygenleveltend.stoincreasetowardsaturation(approximately8.0ppm).TherehavebeentwomajordesignchangeswhichPPRLhasmadetoimprovethewaterchemistryatSSES.5.1.2.1ControlRod.Drive(CRD)PumpSuctionRelocationPPMpreviouslyrelacatedtheCRDpumpsuctionfromthecondensatestoragetanktothecondensatemakeup/rejectline.Thepurposeofthislineistocontrolprimary.cyclewaterinventorybymakingupfromorrejectingtothecondensatestoragetank.Understeadyloadconditionsthislinereceivesaconstantdischargefromthecondenserdue toprimarycycleinfluentwatersourcessuchastheCRDsystemitself.Hence',locatingtheCRDpumpsuctiononthemakeup/regectlineresultsinutilizationofwaterwiththelowestoxygenconcentrationsavailable(essentiallywaterwithfeedwaterquality)mostofthetime.Atthetimetheabovechangewasmade,PALbelievedthatthischange,inadditiontootherchangesmade,wasadequatetosufficientlyreducetheprobabilityofIGSCC.Sincethattime,however,ppM,hasfound.thatcontrollingthe02concentrationasaneffectivemeansofcontrollingIGSCCrequires02controlduringallphasesofplantoperation,notgustnormaloperation.Forthisreason,PHkLadded,amechanicaldeaerationsystem(seesection5.1.2.2),5.1.2.2MechanicalVacuumDeaerationBasedonmorerecentdata,pp&Lhastakenthestepstoadd.amechanicalvacuumdeaerationsystematSSES.This02controlsystemwilloperateduringallphasesofplantoperationexceptnormaloperation.Itwillmaintainthe.02concentrationintheprimarycoolanttolessthan250ppb.Thisrecentchangewasmadeinanefforttoreducethecorrosivenatureoftheprimaryfluidaslowaspossible.ItisPP8cL'spreferencetohavethe02controlsysteminstalledand.operatingpriortoplantstartup.$4143OperatingProceduresLinesconnectedtothereactorvesselwhicharenormallystagnantorexperiencelowflowconditionsmayaccumulatedissolvedoxygenconcentrationswhicharehighrelativetogeneralreactorwater.Startup,Shutdown,HotStandbyand.abnormaleventsareofparticularsignificance.Totheextentpractical,procedureswillbedevelopedwhichwillminimizedissolvedoxygenconcentrationsinstagnantorlowflowlinesand/orreducethetotaltimeofstagnantconditions.ThewaterqualitysamplingsystemhasbeenupgradedinordertoalerttheplantoperatorsofadversewaterconditionsconducivetoIGSCC.Itincludescontinuousmonitoringoffeedwaterandreactorwaterfordissolvedpxygenconcentration,conductivityand.pHand.continuousmonitoringoftheCRDsystemwaterfordissolvedoxygenconcentrationand.conductivity."Thesamplingsystem,automaticallyalarmswhenwaterqualityconditionsconsideredtobeadversetoBWRoperationarereached.

Procedureswillbedeveloped.whichwillminim1zeexcessiveoxygenconcentrationsintheprimarycycleand,toenableplantoperatorstotakeimmediateactiontoprotecttheplantfromprolongedoperationwithadversewaterqualitycond.itions.5.2StressStressaloneisnotparticularlys1gnificantsofarastheoverallcorrosionofmetalsisconcerned.Whencombinedwithacorrosiveenv1ronment,however,theappl1cationofsufficienttensilestressinsusceptiblematerialscanlead.tostresscorrosioncracking.Areduction1ntotaltensilestressinlinesconsidered.susceptibletoIGSCCcould.thereforebeconsidered.beneficial.Inanattempttoreduceoveralltensilestress,pipinglocatedinsidecontainmentand.connected.directlytoeithertheReactorPressureVessel(RPV)ortheReactorRecirculationSystemwasreviewed,todetermineifdesignand/orfabricatingcontributionstotensilestresslevelscouldbereduced..5.2.1DesignStressesThecombinedeffectsofservice,internalpressure,deadweightand.thermalstresseswerereviewedand.allpipingsystemswereconfirmedtohavelayoutswhichlimited.theircontributionstototalstresstoalevelconsideredtobeaslowasreasonablyach1evable.RecognizingtheparticularsusceptibilityoftheCoreSpraySysteminfectionlines,alternateroutingswerechoseninorderthatthethermalstresscomponentoftotalstressisred.ucedby25$.522FabricationStressesThedifficultyinassuringcomplianceunderallshopand.fieldfabricatingconditions,limitstheeffectivenessofprocedureswhichmightbedeveloped.inthisarea.However,s1ncestresslevelsinnon-stressrelieved.austeniticstainlesssteelpipingcanequalorexceed.yield.,anyprocedureswhichmightsignificantlyreducefit-up,initialfabrication,orwelding-induced.stressescannotbeoverlooked..5.2.2.1Fit-upCodetoleranceforalignmentareccmpliedwithtoassureminimumstressfrommisalignmntandminimumdegradat1onoffatigueresistance.5.2.2.2Initial.Fabrication(shop)Thepipematerialispurchased.1nthesolutionannealed.condition.Normally,spoolp1ecesarenotsolutionannealed.duetothedifficultyofmaintainingdesireddimensions.

5.2.2.3Melding-InducedStressPALrecognizesthatwhenausteniticsta1nlesssteelsarewelded,somelevelofresidualstressand.sens1tizationispresent.Acompromisebetweenheatinputcontrolandtheresultingcoolingratemustbeachievedinorderthatacceptablelevelsofres1dualstressand.sensit1zationcanbeachievedwithoutsacrificinggoodpenetrationandfusion.Unfortunately,precisequantitativevaluesofheatinput,coolingrate,etc.,whichwi.llinsureconsistentlygoodqualityweldsresistanttoIGSCCarenotavailable.Therefore,PPMreliesonpastindustrialexper1enceforguidance.PP8Lhasadoptedthefollowingmeasuresforfieldweldingtheapplicable11nes.Thesemeasureshelpreducewelding-inducedstresses,w1thoutcreatingadditionalproblems,toalevelaslowascanbeexpectedusingnormalweldingpractices.5.2.2.3.1HeatInputNopreheat(inexcessoftheacceptableworkingrangeof60Fto150F).b.C~dOInterpasstemperaturelimitedto350F.Blockweldingprohibited.Electrodesize11mitedto5/32"h1ax.forSMAMandl/8"Max.forGTAMwhicheffectivelylimitstheheatinput.5.2.2.3.2JointDesigna.TherootismadewithGTAMut111'z1nghandfedfillerwireoraconsumable1nserttoinsurecompletepenetrationandgoodfusion.b.Theextended-land)ointdesignhasnoinherentproblemswithlackofpenetration,lackoffusionorexcessiveresidualstress.C~Aninertgaspurge1susedpriortoweld.ingandinertgasbackingisused.duringtheweld1ngofthefirstpassestoinsureagood.rootcontourminimizing'theoccurrenceofanycreviceswhichmightleadtocorrosionproblems.Asmoothfinishcontourisspecified(1.e.,noexcessiveundercut,excessivereinforcement,coarser1pples,etc.)toreducetheoccurrenceof"notches"whichcandetrimental+affectfatiguestrengthorcorrosionresistance.

105.2.2.3.3FillerMetalTominim1zemicrofissuringand,sensitizationproblems,308Lfillermetalor309and.309Lfillermetalisspecified.w1thminimumdeltaferritecontentsof8percentand.5percentrespectively.5.2.2.3.4CleanlinessTopreventcontaminationofthejoint:a.Grease,oilandothercontaminantsareremoved.fromthejointand.thef1llermetalpriortomakingtheweld.b.Onlymarkingcrayons,chalk,1nkandtemperatureindicatingcrayonswhicharecertified.tobelowinhalogenand,sulfurcontentareused.c.Onlycleaningsolventswh1charenotharmfultoausteniticstainlesssteelareused,.d..Stainlesssteelwirebrushesareused,.e.Grindingwheelsusedonothermaterialsarenotused.onstainlesssteel.f.GrindingwheelsarenotusedonI.D.pipesurfaces.Ifcleaningisnecessary,flapperwheelsshallbeused.TheexistingmethodsandproceduresforQualityControl/QualityAssuranceoftheaboveareadequatetoinsurethattheseprovisionsarefollowedand.thattheresultswillbeconsistentw1thwhatwasspecified..Restrictionsconsistentwiththoseaboveapplyequallytoshopand.fieldsubcontractwelding.5.2.3MethodsofStressReductionDuetocontinuedreportsofIGSCCsincePPMfirstformd.apositiononthesubject,PP&Lhassteppeclupitsmonitoringoftheproblemanditspossiblecountermeasures.Thosecountermeasuresthatarebeinginvestigated./evaluated.whichdealwithstressreductionareSolutionHeatTreatment(SHT),HeatSinkWelding(HSW),and.Induct1onHeatingStressImprovement(IHSI).5.2.3.1SolutionHeatTreatmentThisIGSCCcountermeasurestressrelievesshopwelcls.beforethesectionsofpipeareshipped.tothefieldforinstallation.Thismethod.canonlybeusedonshopweld.s,and.then,onlywhenthepipeshavenotbeeninstalled..

ForSSESmostofthetargetlinesforwhichnoothercountermeasures(i.e.,materialchanges)havebeentaken,havealreadybeeninstalled..However,theshopweldsontherecirculationgetpumpr1sersunderwentSHTbecausePPMbelievedtheselinestobeextremelysusceptibletoIGSCC.Thef1eld.weldendsoftheriserswerealsocorrosionresistantclad..Thisprocesswillbed.iscussedinalatersection.5.2.3.2HeatS1nkWeldingThisIGSCCcountermeasurerequirescoolingtheIDofthepipewithcoolingwateraftertherootpassoftheweldhasbeencompleted.Thisprocesscauses-theresultantresidualstressesontheIDofthepipetobecompressiveratherthantensileaswould.befound.withnormalweldingpractices.ResultantcompressivestressespreventXGSCC,ThiscountermeasurehasnotbeenusedatSSES.However,BechtelispresentlyperformingafeasibilityevaluationontheuseofHSWforselected.linesatSSES.5.2.3.3.InductionHeatingStressXmprovementThisIGSCCcountermeasureisused.afterthefieldweldshavebeencompleted..TheprocessinvolvesheatingtheO.D.ofthepipewithaninductioncoilwhilecoolingtheI.D.withcoolingwater.ThisprocesscausestheresultantstressesontheI.D.ofthepipetobecompressiveratherthantensile,thuspreventingIGSCC.ThisprocesshasnotbeenusedatSSES.PresentlyGE1sintheprocessofdeveloping/qualifyingthisprocedureforuseonBWR'sintheUnitedStates(Reported.lytheJapanesehaveused.thisproceduresuccessfullyontheirnuclear~powerplants,).PP8cLintend,stotracktheprogressofGEand.usetheprocedureonsusceptiblelinesifand,whentheprocedureisdetermined.tobefeasible.5.3hfaterialDuetotherestrictionsofcoolantchemistryandtotaltens1lestresslevels,theuseofsubstitutematerialswhicharelesssusceptibletoXGSCCwereconsidered..ThelackofsignificantoperatingdataformaterialsotherthancarbonsteelorType304and.Type316stainlesssteelslimitstheoptions,however.Dur1ngthedesignoftheplant,attentionwasgiventominimizingproblemsrelatedtogrosscorrosion.StainlesssteelwaschosenforCoreSpraylinesinsidecontainment,condenserand.'feedwaterheatertubes,and.ASSAMA155GradeKC70,Class1feedwaterpipe.PP8cLis,therefore,unwillingtousecarbonsteelasanIGSCCf1x.

TheprincipaldrawbacktothecontinueduseofType304and.Type316stainlesssteelforNSSSpipingistheirsusceptibilitytoIGSCC.PP8cLbelievesthissusceptib1lityisrelatedtosensitizationwhichoccursadjacenttoaweldintheheat-affectedzone.Sensitizationisatemperaturedependentmetallurgicalphenomenonwhichresultsintheformationofchromiumcarbideatgrainboundarieslocatedintheheat-affected.zoneofaweld.Therefore,1twaslogicalto11mitthecarboncontentofsusceptiblelines.Originally,thehistoryoftheIGSCCproblemformedthebasisoftheassumptionthatthecomb1nationofresidualstressandsensitizationwasinsufficienttoresultinahighprobabilityoffailureduetoIGSCCforlinesinthereactorcoolantpressureboundarylargerthan12"diameterNPS.Thefocusforpossiblematerialsubstitutionwas,therefore,onthoselineswh1chwerelessthanorequalto12"diameterNPS.Anysuchsubstitutionswouldapplyequallytopipefittings.However',valvesand.containmentpenetrationflued,headsarenotincludedastheyareofsufficientmasstobesubstantiallylesssusceptibletoIGSCC.~Basedontheaboveassumption,Type304Lstainlesssteelwasusedforallstainlesspipingwithinthereactorcoolantpressureboundarywhichis4"diameterNPSorsmallerwithasupplementalrequirementof0.030percentmaximumcarbon(withtheexceptionoftheRecirculat1onSystemDischargeGateValve'ypassLine).Sta1nlesspipinglocatedwithinthereactorcoolantpressureboundarywhichisgreaterthan4"butlessthan12"diameterNPSwillbeType304stainlesssteelwithamaximumcarboncontentof0.030percent.1hesetwomaterialsarevirtuallyidenticalmetallurgicallybutPPEcLisunwill1ngtosacrificethemechanicalpropertiesof304forcertainpipingsystems.Tablelident1fiespipingforwhichachangeinmaterialwasjustified,thematerialprevious+specified,andthereplacementmaterialchosentomitigatetheprobabilityofIGSCC.Sincethetimetheabovematerialchangesweremade,additionalinc1dentsofIGSCChaveshownthattheassumptionthatonlythoselineswhichare12"d1ameterNPSorlessaresusceptibletoIGSCCisincorrect.Therefore,alllinesmustbeconsideredwhenattemptingtoeliminateorreduceIGSCC.Inadditiontosimplemater1alreplacement,theother"mater1al"relatedIGSCCcountermeasurewhichcanbeevaluatedisCorrosionRes1stantCladding(CRC).Thiscountermeasurecombinescladdingthefieldweldedpipeendswithahighlycorrosionresistantmetalwithsolutionannealingwhicheffect1velyprovidesacorrosionresistantbarrierbetweentheheataffectedbasemetaland,theoxygenatedreactorcoolant(corrosivefluid.).

13Asdiscussed.inSection5.3.4ofth1sreport,PPM,utilizedCRContherecirculationgetpumprisers.Duetotheirparticularsignificancewithregardtothecurrentproblem,theCoreSpray,ReactorRecirculationSystemDischargeGateValveBypassLine,ControlRodDriveReturnLine,andRecirculationR1serPipesarediscussedbelow.5.3.1CoreSpraySystemThatportionofthecorespraysystemwhichislocatedwithintheprimarycontainmntwill,forSusquehannaSES,bema'defrom12"diameterNPS,Type304StainlessSteelPipewithsupplementalmaximumcarbonlim1tationof0.030percent.pipeandfittingswillbehandledsimilarly.532ReactorRecirculationSystmDischargeGateValveBypassZineFromanoperationalstandpointpp&Ldoesnotwishtodeletethislin.Itisconsideredimportantfromthefollowingstandpoints;l.Itprovidesameansofpreheatinganidlerecirculationloop.2.Itreducesthermalshockseenbythecomponentsofan1dleloop+/3.Itprovidespressureequalization.onbothsidesofthedischargegatevalvetoassureproperventingandclosureofthevalve.Iteliminatescuttingandwiredrawingofthedischargegatevalveseat.The4"diameterNPSlinewillbefabricated.fromType304stainlesssteelwithasupplementalmaximumcarbonlimitationof0.030percent.Thismaterialchoiceresultsfromthedes1retolimittheprobabilityofIGSCCwhileretainingthemechanicalpropertiesofandtheexistingstressanalysisforType304stainlesssteel.Pipeandfittingswillbehandledsimilarly.533ControlRodDriveReturnLineThis3"diameterlinewaschang'edfrom304SSto304LSSwhich,1twasbelieved.,would.solvetheproblemofIGSCC.Subsequenttothischangetherewerenumerousreportedinc1dentsofcrackingintheCRDReturnLinenozzle.Theseincidentsofcrackingwereattributedtoexcessivethermalgradientsacross thenozzleratherthanIGSCC.GeneralElectric'srecommendationwastodeletethereturnlineand.makeotherchangestothesystemtomainta1nthesystemdesignfunction.PPEcLconcurred..withGE'srecommendationand.deleted.thereturnlin.Thisaction(1)eliminatedtheproblemofnozzlecrackingduetothermalgrad.1entsand.(2)eliminatedthepossibilityofpipcrackingduetoIGSCC.5.34Rec1rculationRiserPipesThe10'ecirculationriserp1pesleadingfromtherecirculationheadertothegetpumpshaverecentlyexperiencedIGSCCatotheroperatingplants.Thecrackshavebeenformed.intheheataffected.zonesofthethermalsleevetosafeend.attachmentweld.s.Thepipeshavebeenfabricatedfrom304sta1nlesssteel.Thesafeend.sareImonel600,and.thenozzlesarecarbonsteelclad.withstainlesssteel.PP8:LhasmadethefollowingchangeswhichwillminimizethepossibilityofthesepipescrackingduetoIGSCCofSusquehannaSES.1.ThepipetosafeendandpipetoteeweldswillhavetheirID'scladwith308Lweld,materialintheheataffected.areapriortowelding.2.Theriserpipeswillbesolutionheattreated.toeliminateresidualstressesfromtheelbowtopipeshopweld.s,andtheCRCprocess.3.Theseweldswillthenbefieldwelded.using308Lweldingrods.Thisprocesswillprevent304stainlesssteelintheheataffectedareafromcomingincontactwiththeprocessfluid.

156.ReferencesSourceGENRCAS%1DocumentNEDO-21000NUHEG75/067"StressCorrosionCrackingofMetals-AStateoftheArt"DateJu~,1975October,1975October,1971NATO"TheTheoryofStressCorrosionCrackinginAlloys"October,1971"FundamentalAspectsofStressCorrosionCracking"September,1967UnitedStatesSenateJointHearingConcerning"NuclearRegulatoryCommissionActionRequiringSafetyInspectionsWhichResultedinShutdownofCertainNuclearPowerPlants"February,1975 16SUSQUEHANNASTEAMELECTRICSTATIONTABLZ1MA'JRRIALCHANGESPipeDescriptionHead.SprayCoreSprayInfluentSize~NPS12IIpreviousMaterialType304SSNewMaterialCarbon-Limited.Type304SSControlRod,Drive3"HydraulicReturnCRDReturnLineHasBeenDeleted.StandbyLiquid.ControlReactorWaterCleanupEffluent1-1/2"4IIType304SStofirstvalvepthenCarbonSteelType304LSStofirstvalve,thentoCarbonSteelInstrumentpipingVent,Drain,and.TestConnectionsShownonFigure11",2"Type304SS4IIType304SSType304LSSType304LSSRecirculation'ystemBypassBottomDrain4II4IIType304SSType304SSCarbon-Limited,Type'304SSType304LSSTFO:bah 17M~1MCONTAINMENTPENETRATIONHEADSPRAYREACTORVENTTOINSTATMVENTVENTTOlASt,VESSEI.VENTNLIAINSTEAMlFEEOIVATERTOVESSELI6>>MAINSTEAMFEEOWATERTOVESSELSLCTESTCONN'ECTIONVENTVCONNECTIONDRAINCONNfCTIONSTANDBYLIGVIDCONTROLSYSTEMREACTORIYATERCLEANUPSYSTEMRESIDUALNEATREMOVALSYSTEMCONTROLAODDRIVESYSTEM12"CORESPRAYM1>>121>>12"REACTORPRESSUREVESSEL12"I>>1>>>>COR'ESPRAY,CRORETURN(DELETED}LINE>>RHRRETURN24"AECIRCYLOOPJ24RECIRC+LOOP24"24RHRRETURNI>>M120RHRSUCTIONRECIRCg26"PILOO20>>20"4GOTTOMDRAIN4>>4>>4>>RECIRC9LOOPINSTCONN11/2"SLCRWCUSUCTION6"6"INSTCONNV1>>41"LTM0IOOISOBGIFigure1