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    Current

    PlasmaScience&Technology,Vo1.6,No.1,Feb.2004

    CurrentStatusoftheKSTAREngineering

    J.s.Bak,K.Kim,C.H.Choi,Y.K.Oh,B.C.Kim,N.I.Her,H.L."fang,G.S.

    Lee,andtheKSTARTeam

    KoreaBasicScienceInstitute,52YeoeunDong,YusungKu,Daejeon305333,Korea

    AbstractAsthereissubstantialprogressintheKSTARtokamakengineering,allthemajor structuresandsub-systemsareunderfabricationandinprocurementphase.Thevacuumvessel,

    port,cryostatcylinder,lid,andbellowsarebeingrigorouslyfabricatedinthefactory.Thelower

    partoftheKSTARsuchascryostatbaseandgravitysupporthasbeenalmostfinishedinits fabrication.Therearealsogreatprogressesandsignificantresultsinmanufacturingofthesuper-

    conductingmagnet,includingfourToroidalField(TF)coils,lowerandupperPF7coilswhichare

    thelargestPoloidalField(PF)coils.TheTF00coil,whichhasbeenmadefortestandbackup

    oftheTFmagnetsystem,wassuccessfullytestedinthecool

    downandcurrentcharging.Asthe

    fabricationsandprocurementsofmajorstructureshavebeenactivelyproceeded,assemblyworks

    werealsolaunchedfromAug.2003.Moredetaileddescriptiononthesestatus,results, andplans

    willbedescribedinthispaper.

    Keywords:KSTARtokamak,vacuumvessel,magnet,cryostat,tokamakassembly PACS:52.55.F;74.25.H;85.1o.F

    1Introduction

Afterthecompletionofpreliminaryconceptualde

    signfortheKSTARin1998,substantialprogressin themaintokamaksubsystemshasbeenmadewith industrialmanufacturersbySeptember2003.The overallengineeringdesignofthedevicewasopti

    mizedthroughameticulousreviewprocess.Forthe sakeofcompletenessaschematicviewoftheKSTAR andthemainspecificationscanbefoundinRef. fl1.

    AsofSep.2003,theprojectisinthephaseoftender. Thefabricationofvacuumvessel,cryostat, welded

    bellowsandsupportingstructuresiswellprogressed. HyundaiHeavyIndustriesfHHI)hasbeenmanu~c

    turingthevacuumvesselandcryostatinthefac

    torysinceMay2002.Onsiteworkforcryostatwas

    startedfromMay2003.

    Themanufactureofsuperconductingcoilsisalso onschedule.NowthewindingofTF04,PF7Ucoil isproceedingactively.ThefirstTFcoilfTF00)was successfullytestedinSamsungSuperconductingTest Facility(SSTF).Thecoilwassuccessfullytestedin cooldownandcurrentchargingwithoutanyprob

    lems,andthesuperconductingphasetransitionwas confirmed.Magnetstructuresareinthestageoften.. deraftertheelaborateengineeringmodifications. Thedetailassemblyplanhasbeendnedtoas

    surecompliancewithassemblyrequirementandto minimizethesubsequentcorrectiveoperations. The

    tokamakassemblywillstartfromDec.2003aftersite preparationandassemblytooling.Assemblyopera- tionswillconclude,approximately36monthslater, withthesuccessfulcompletionoftheintegratedsys

    terntestsandtheachievementofthefirstplasma. 2cuumvessel

    TheKSTARvacuumvesselconsistsoftheinner andoutershells,72portswithbellows,andtheleaf springstylesupports.Thevesselbodyisadouble

    wall,Dshapedstructure.Intheinterspacebetween

    theinnerandoutershell,thereare32equally-spaced poloidalribsand2toroidalribs.

    ThesheIIs,port

    stubwalls,andribsformtheflowpassageofvessel bakingandcoolingwater.TheKSTARmcuum

    Theprojectsupp.rtedbytheK.reanMinistry.fScienceandTechno1.gyunderth

    eKSTARprojectc.ntract

Fig.1FabricationjigforVacuumvessel

    vesselistobefabricatedin

    sectors(180,157.5degrees)

    22.5degreesspan.

    thefactoryastwolarge

    andonesmallsectorof

    Aftertheextensiveengineeringdesignactivityand prototypefabrication,thecontractformanufactur- ingvacuumvesselwasmadein2002withHyundai HeavyIndustryfHHI).Tomakethetorusshaped

    vacuumvessel,arawmaterialfSA240316LN)sur-

    faceisbutiedandashapeofthree-dimensionsis

formedbyan1,500tonhydraulicpress.Thefab

    ricationtoleranceoftheformedcomponentsisless than5mm.Therequirednumberoftheformed

    shellforvacuumvesselbodyisabout170.Eachshell formedismachinedandcleanedfornextprocedure. Tominimizetheweldingdistortionofvesselbody andmeetthedimensionalaccuracyrequirement,the specialjigandfixtureisdeveloped.Thefittedviewof thepoloidalribsandtoroidalribsintothefabrication jigisshowninFig.1.ThejiginFig.1isforflareand knucklepartofDshapedvesselbody.Inthisconfig- uration,thepoloidalribsandtoroidalribsarealso usedasapartofjigforinnerandoutershellassem

    bly.Aftertheassemblyofjigframe,theinnerand outershellfitupandweldingarefollowed.Fig.2

    showsthelowerpartofonequadrant.Foronequad- rant,thereare2jigframesforupperandlowerpart ofDshape.Aftertheweldingoflowerandupper partofonequadrantisfinished,thestraightsection ofDshapeisinsertedintotheupperandlowerpart ofvesseltomakethefullyshapedauadrant.TheD

    2160

    PlasmaScience&Technology,Vo1.6,No.1,Feb.2004 Fig.2LowerpartofVaCUUITIvesselquadrant shapedquadrantismachinedforportopeningand theportstubisweldedintotheportopeningofthe vacuumvesselbody.Thepressureandleaktestfor eachquadrantwillbeperformed.Tomakeeachsec

    tor,twoquadrantsareassembledandwelded.The

    leakageofquadrantto-quadrantweldingjointofeach sectorisalsoleaktested.Finally,twosectorsandone smallsectorof22.5degree,consistingoftwentyfour smallshellsandribcomponentswillbecombinedto makethetorus.The72portsmanufacturingprocess issimilartothatofvesselbodyfabrication.Theraw materialsurfacefinish.3Dforming.fitupandweld.

    ingofcomponentsaregoingon.Eachportconsists ofstraightsection,bellowsandflange.Thestraight andflangepartsaremadeinvacuumvesselmanu- facturerfHHI).ThebellowsaremadeinJapanese company,ValquaSeiki.Finalweldingassemblyof wholeportcomponentsisperformedinHHI.The portwithbellowswillbeweldedwithvacuumvessel bodyandcryostatportstubinfinalsiteassembly. 3Magnet

    3.1coilmanufacture

    Accordingtogreatprogressintheresearchforthe superconductingmagnetmanufactureasdescribed inRef.variouskindsofsuperconductingmag- netsfortheKSTARarenowunderactivefabrica tion.Thefull-sizeToroidalField(TF)prototype

    J.S.Baleeta1.:CurrentStatusoftheKSTAREngineering Fig.3TF00coilafterVPI

    coilnamedTFO0,andthetwocoilsforbackground magneticfieldgeneration(BKG01,BKG02)areSUC- cessfullydevelopedandmostofthefabricationpro- ceduresaresettleddown.Fig.3showstheTF00coil afterVacuumPressureepoxyImpregnation(VPI).

The1stTFcoilnamedTF01isnowunderleak

    testafterheattreatment.The2nd(TF02),the3rd fTF03),andthe4th(TF04)TFcoilsareunderpro- cessofheattreatment,insulationtaping,andwind- ing,respectively.BothofthelowerPF7(PF7L)and upperPF7fPF7U)coilsarebeingmanufacturedin theon-siteareaduetothedifficultyintransporting theselargecoils.ThePF7LcoilisnowunderVPI aftergroundwrapping,andthePF7Ucoilisbeing woundinthewindingstation.Fig.4showsPF7L coilthatiswaitingforfinalVPI.

    3.2Magnetstructuredevelopment

    Theengineeringdesignandprototypestructure fabricationofthemagnetstructurehadbeencorn- pletedStructural,thermal,andelectricalproper

    tiesofthemagnetstructurewereconsideredthrough theengineeringdesign.Inaddition,fabricabilityhad beenconfirmedthroughprototypestructurefabrica

    tion.

    MajordesignconceptsoftheTFandCScoilstruc

    turesenvisageawedgedD?shapestructureandapre.

    1oadingstructure,respectively.ThePF5coilstruc

    turehasahinge-type,andthePF6andthePF7 coilstructureshaveaflexible-type.TheoneTFcoil Fig.4PF7LwaitingforfinalVPI

    structurethatisfullofweldingtypeenvelopsone TFcoil.andeachTFstructureisconnectedthrough boltsandshearkeyswithelectricalinsulationin toroidaldirection.TheTFcoilstructuresaresup- portedbygravitysupportsallowingaradialmove-

    mentduetothermalcontractionofmagnetsystem. TheCSstructureissupportedontheTFcoilstruc

    tureandsuppliesaverticalcompressionof15MN topreventlateraldisplacementduetorepulsiveforce betweentheCScoils.ThePFcoilstructuresarealso supportedontheTFcoilstructurewithindividual basementthatisweldedontheTFcoilstructure, Anofthesestructuresneedhighmechanicalstatic andfatiguestabilityatlowtemperaturetoendure highmagneticenvironment,sowewillusestrength

    enedstainlesssteelasthematerial,Thedetailsof theelectromagneticandstructuralanalysescanbe foundinRef.I31.

    WlehavefabricatedoneprototypeTFcoilstruc

    tureandoneprototypePF5coilstructurethatare fabricatedbvHHI.Allowablefabricationtolerances are1lninininboardlegpartand2mminout

    boardlegpart.Fig.5showstheTFcaseandfabrica- tiontolerancesaftermachininginsidewal1.Because outsidewallshouldbemachinedafterTFcoilen- casing,itstolerancesarelargerthantheallowable values.WehaveusedJJ1materialthathasahigh yieldstrengthofmorethan1000MPa.W_ehadto considerawallthicknessmarginof5nlnltoabsorb weldingdeformationandmachineinsidethecaseto meetthefabricationtolerances.Thecoolingtube 2161

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    PlasmaScience&Technology,Vo1.6,No.1,Feb.2004 Fig.5PrototypeTFcasestructure

    (a)TF00cooldownhistory

    -,...

    _?7/

    about617InQat3K

    ,abmtOna~20KI

    Fig.6Experimentalresultsin2ndcampaign thatisseamlessSUS316L,withaninnerdiameterof 4mm,alengthof12m,andanumberof28iswelded intotheinsidewallofthecasealongperimeter.The prototypePF5coilstructurehasfabricatedwithan overalltoleranceof0.1mm.

    3.3TF00coilcoo1.downtest

    TheprototypeTFcoiltesthasbeenaccomplished followingthefirstandthesecondcampaigninthe SSTF.Thefirstandthesecondcampaignwereper.. formedbyJan.2003andSep.2003,respectively. Afterthecoilinstallationinthecryostat, final

    2162

(b)Coilresistance

    inspectionwasdoneincludingtheelectricisolation checkandheliumleakcheckatroomtemperature. TheCI.yostatwasevacuatedto5.3×10Paatroom

    temperature.Afterfillingliquidnitrogenintothe therma1shieldinthecryostatthecol1hasbeen cooleddownwithinthespecifiedtemperaturedif- ference.ThecoilcooldowndurationWas15days

    inthefirstcampaignand9daysinthesecondCalTl

    paignasshowninFig.6(a).Theresidualresistance ratio(RRR)ofthecoilwasmeasuredtobeover200 asshownintheFig.6(b),thevalueofwhichsatisfies therequiredvalueof100intheKSTARdesign.The lIol3l!ou

    J.S.Baketa1.:CurrentStatusoftheKSTAREngineering Relativetime/sec

    12

    10

    Relativetimelsec

    Fig.7Currentrampupandfastdischargeat21.7kAduetothequenchinthecurrentfeeder

    superconducting(SC)phasetransitionofthecoilwas detectedat18K.Whenthecoi1wasfullycooled,the supercriticalheliumcouldbesuppliedintothecoi1 bycontrollingthevalvesintheheliumrefrigerator. Thehvdraulicparametersofthesupercriticalhelium inthedistributionboxweremeasuredasfollows:the supplyandreturntemperatureswereabout5,0K and5.4K,respectively,andthesupplyandreturn

pressureswereabout5.3barand3.0bar,respec

    tively.Theheliumflowrateofthecoilwasabout i5g/sintotalwhenthesupplytemperature,supply pressureandpressuredifferencewereabout5.2K, 5.2bar2.2barrespectively,Heliumflowbetween 4channelswereuniformwithin10%deviationeach channelisinteractivewithneighboringchannelsbe- causeofthecontinuouswinding.

    3.4TF00coilcurrenttest

    Thecoilhasbeenrampedupanddischarged23 timesduringthesecondcampaign.Beforethecoil wasfullychargedaccordingtothespecifiedvalue, quenchtestshadbeencarriedoutbyintentlyheating thecoolingtubeonthe.inletlinesofthecoilandcur- rentleadswiththecoilchargedto5kA.Thecoilwas repeatedlyrampedupinstepsof5kA,10kA,15kA, 20kA25kA.and30kAwithvariousrampingrate andfo1lowedbyvariousdischargessuchasslowdis

    charge,safetydischarge,andquenchdischarge.The coi1wasoperatedinsteadystatewithoutquenching upto33kA.Themaximumcurrentwaslimitedbe- lowthenominaloperatingcurrentof35kAbecause ofthestructura1weaknessoftheSCbuslinesup.

    porters.ThecurrenttestresultsonTF00coi1are showninFig.7

    4Cryostat

    TheKSTARcryostatisalargevacuumvesselsur- roundingtheentiretokarnakmachinewithasingle- walledcylindricalshell,adomeshapedtoplid,and

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