NationalInstitutesforQuantumandRadiologicalScienceandTechnology(QST),Rokkasho,Aomori,JapanaNationalInstitutesforQuantumandRadiologicalScienceandTechnology(QST),Naka,Ibaraki,JapanbGraduateSchoolofEngineering,NagoyaUniv.,Nagoya,JapancGraduate SchoolofEngineering,OsakaUniversity,Osaka,Japan

StudiesofPlasmaExhaustScenarioandDivertor DesignforJADEMO

NobuyukiAsakura,K.Hoshino,H.Utoh,Y.Someya,S.Suzukia,H.Kudo,S.Tokunaga,Y.Homma,Y.Sakamotoa,R.Hiwatari,

K.Tobita,K.Ezatoa,Y.Sekia,N.Ohnob,Y.Uedac,andJointSpecialDesignTeamforFusionDEMO

IAEA2ndTechnicalMeetingonDivertor ConceptsSuzhou,China,13-16November2017

Contents

2.PowerexhaustinJADEMO,andthedivertor simulation

3.EngineeringdesignforJADEMOdivertor

4.Summary,futureworkandissues

1. Introduction:DEMOspecialdesignteaminJapanBADEMOdesignactivity,andpowerexhaustconcepts

Joint Special Design Team for Fusion DEMO

1.DEMOdesignactivityinJapan:BADDA,SpecialdesignteamJoint Special Design Team for Fusion DEMO

Total83members(incl.site&visiting,2017June)QST28,NIFS3,Univ.28,NIMS 1,Makers/Industries23

Similarsize(8-9m),Pfusion (1.7-2GW),Pheat (430-460MW)

Parameters JADEMO EUDEMO1 ITER(inductive)

Size&Con

figuration Rp / ap (m) 8.5/2.42 9.1/2.94 6.2/2.0

A 3.5 3.1 3.1k95 1.75 1.59 (1.70)q95 4.1 3.2 3Ip (MA) 13.5 19.6 14BT /BTmax (T) 5.94/12.1 5.7/12.3 5.3/12

AbsolutePerform

ance

Operation Steady-state Pulsed 2hrs ~400sPfusion (MW) 1694 2037 500Pgross (MWe) 588 914 --Paux (MW) 96 50 73Q 18 41 10

Pa+Paux (=Pheat MW) 435 457 173Neutron(MWm-2) ~1 ~1 0.5

Norm

alize

dPerfo

rmance HH98y2 1.3 1.1 1.0

bN 3.4 2.6 1.8fBS 0.61 0.35 0.15ne/nGW 1.2 1.2 ~0.9

EUDEMO1(pulsed2hrs)[Wenninger,etal.Nucl.Fusion2017]

JapanDEMO(steady-state)(increasingk95 andseeding)[Sakamoto,etal.IAEAFEC2014,Asakura,etal.Nucl.Fusion2017]

Joint Special Design Team for Fusion DEMO

CommonmissionsforJAandEUDEMOs:・Electricgeneration,・Fuelgeneration,・Highduty-cycle,・ Remote-maintenanceinhighneutrondose,・Safety,・ Plasmacontrol&Power handlinginlong-pulse/steady-state

PowerexhaustscenarioanddesignconceptinJAandEU

EUPowerexhaust(pulse2hours):HigherIp =20MA,andne =8.7x1019m-3,⇒ Largeradiationlossinmainplasmausinghigh-Zimpurityseeding,toreducePsep/Rto17MW/m(ITER-level)

Parameters JADEMO EUDEMO1 ITER (Q=10)

Powerexhaust

line-ave. ne (1019m-3) 8.5 8.7 ~10nimp/ne (%) 0.60 (Ar) 0.039(Xe) N2,Ne,Ar…

Pa+Paux(=PheatMW) 435 457 173

Pradmain (MW) 177 306 ~70

Pradmain/Pheat 0.41 0.67 0.40

Psep (MW) 258 154 ~100

Psep/Rp (MWm-1) 30 17 16

PowerexhaustscenarioforDEMOplasmasandthebaselinedivertordesign havebeenstudiedwithahighpriorityinJAandEU.・ EUandJAstudieshavecovereddivertor physicsandengineeringaspects:Water-cooledsingle-nulldivertor,operatingwithPlasmadetachment.・ Bothconceptsrequirehighlyradiation(frad =Prad/Pheat~80%)tohandlewithITER-levelpeakheatload(10MWm-2),whilebalanceoffradmain andfraddiv isdifferent:

Systemcodepredictions(JA:TPC,EU:PROCESS)

JAPowerexhaust(steady-state):LowerIp =13.5MAduetohigherq95(4.1),andexpectinggoodplasmaperformance,⇒ Largepowerhandlinginthedivertor:

Psep/R~30MW/m

CommonandComplementalworksweresummarizedinAsakura,etal.ISFNT-132017.

Joint Special Design Team for Fusion DEMO

⇒ Twoapproacheswillprovideimportantcase-studiesforfuturedecisionofthedivertor design.

ImpurityseedingintoJADEMO2014 (Ip=12MA,k95=1.65,Pfusion~1.5MW,HH98(y2)=1.3):・ Fusionpower (Pfusion)wasreduced1.4)wasrequiredtomaintainWth andbN.k95=1.75 isproposedtoincreaseIp =13.5MA, =7.2x1019m-3,Pfusion >1.5GW⇒ Conductingshelldesign(verticalstabilitycontrol)isimproved(Utoh,ISFNT-13,2017)

2.PowerexhaustandImpurityseedinginJADEMOscenario

k95=1.75:=7.2x1019m-3

PowerexhaustbyAr seeding:increasingnAr/ne=0.5-0.75%⇒ Pradmain=150-205MWand Pfusion =1.75-1.65GW

fradmain =Pradmain/Pheat =0.35-0.45(ITER-level)⇒ Psep=285-205MW,i.e Psep/R=34-25MW/m

(assumingnHe/ne=7%,nW/ne=10-5)

systemcodestudy

LargepowerhandlingisrequiredforJAdivertor,whileHH98(y2)~1.3,bN =3.4,Pfusion>1.5GW ismaintained.

Joint Special Design Team for Fusion DEMO

Note:L-HPth (Martin,J.Phys.:Conf.Ser.2008):need databaseofHtoLthresholdpoweratZeff >2-3,andPth atfGW >1?(Huber,Nucl.Metter.Energy2017)

SONICsimulation:self-consistentlysolvedbyiterationofplasmafluid(SORDOL),neutral(D)MC(NEUT2D)andimpurity(Ar)MC(IMPMC)codes

Longlegdivertor:Ldiv-out=1.6and2.0mwasinvestigatedtodeterminethesize

・Atcore-edgeboundaryr/a=0.95: exhaustedpower(Pout=250MW),particle(GoutD+=1x1022s-1)・Transportcoefficients:ce=ci=1m2/s,D=0.3m2/s(sameasITERcalc.),Driftsarenotincorporated.・CoveringtheconnectingSOL:rmid <3.2cm.

Divertor physicsstudybySONICsimulations

Pout=250MW

Spump=63m3/s

SONIC:K.Shimizu,etal.,J.Nucl.Mater.2003,H.Kawashima,etal.J.PlasmaFusionRes. 2006,T.Eich ‘sscaling:Nucl.Fusion2013

Ldiv=1.6m

Joint Special Design Team for Fusion DEMO

1.9mm

5.3mm

Tesep=350eV

Tisep=740eV

nesep=2.4x1019m-3

Tesep& Tisep areincreased:2-3timeslargerthanITER⇒ lq// near-sep. becomessmallwhilec isthesame:lq//=1.9mmisstilllargerthanEich’s scaling(1.3mm).c & Dto1/2-1/4(Kikushkin JNM2013)isinprogress.

OptimizationofAr seedingrateatPradedge+sol+div/Pout=0.8nesep isincreased(1.8to2.4x1019m-3),Ar puffrateisminimized(4.2to3.3x1020/s),whereradiationpowerfraction,(Pradedge+Pradsol+Praddiv )/Pout =0.8,isfixed.⇒ Pradsol isincreasedfrom26to36MW,andPraddiv isdecreasedfrom162to150MW.Innertarget: TotalpowerPtarget = 52-66MW,andpeakqtarget =5-8MW/m2Outertarget:Ptarget isreducedfrom80to60MWandpeakqtarget from8to4MW/m2,

sincetheplasmadetachmentisextendedtoupstreamandwider(next).

Joint Special Design Team for Fusion DEMO

nAr/ne inSOL decreasesto0.42%(comparabletomainnAr/ne =0.5-0.7%:systemcode),imp. shielding,(nAr/ne)div/(nAr/ne)SOL,isimproved⇒ appropriatefuel&Ar puffrates

(nAr/ne)div/(nAr/ne)SOL,nAr/nePtarget qtarget

Psep=235MW

Targetheatload

Pradmain =180MW(Pradmain/Pheat =0.41)

PradSOL+div =186MW(PradSOL+div/Pheat =0.43)

Pheat (=Pa+Padd)= 430MW

PradSOL =33MW

Praddiv =153MW

Pdiv=202MW

PowerexhaustforPradedge+sol+div/Pout=0.8,D2puff:100Pam3/sPowertodivertors (Pdiv):202MW(>2xITER),Divertor radiation(Praddiv):153MW(~3xITER)innertarget:Fulldetachment(Te,i~1eV)outertarget:Partialdetachment(r<14cm)

Praddiv-Out=81MW

RadiationandelectrontemperatureprofilesforLdiv=1.6mdivertor case

Praddiv-In=72MW

(Dpuff:100Pam3/s)

Wrad

Te

Joint Special Design Team for Fusion DEMO

Pradtot/Pheat =0.84(systemcode&SONIC)

Controlofradialpeakanddetachment:SimulationvsExperiments・ Controlofthestrongradiation(detachment)inthedivertor leg(Ldiv >1mITER-level)isnecessarytoproposethepowerexhaustconceptanddivertor design.

RadiationisenhancedneartheX-pointanddetachmentexpandsatthetarget⇒ reducinginTeped,HH98(y2)

・ InDEMO(andITER)withhighTe andq//,radiationpeakcanbemaintaininthedivertor.・ Pressurelossatthedetachmentissmall:n(Te+Ti)+mini(Vi)2:(Xp)3.4x103 ->(div)1.6x103Pa

0.6m1.0m

Praddiv/Pheat >0.6Nseeding:H98=0.9frad ≤90%Type-IIIELMs

H98=0.7frad ≤75%

Type-I/noELMs

Ar seeding:H98=0.7-1frad ≤90%Type-IIIELM

Krseeding:H98=0.65frad ≤60%

H/Ltransitions

M.Bernert,Nucl.Mater.Energy2017

JET-ILWAUG

DetachmentplasmaatinnerandoutertargetsInnertarget:plasmaheatloadisreduced,whileionizationstilloccursatTe =1-2eV.⇒ peakqtarget ~5MW/m2:surfacerecombinationloadisadominantcomponent.Outertarget:“partial”detachmentisproducedinrtarget <14cm.⇒ peakqtarget ~5MW/m2:plasmaheatloadisdominantattheattachedregion, and

radiationloadisalsolargeduetosignificantradiationlossnearthetarget(above<10cm).

Pintotal =41MW Pouttotal=66MW

Joint Special Design Team for Fusion DEMO

Note:W-targeterosionintheouterattachedareaisanissueforSteady-Stateoperation.

attachdetach detachDetach:recomb.

attach:ionization

LowerPrad case:Pradedge+sol+div/Pout=0.75(Pradtot/Pheat~0.8)

Outertarget:narrower“partial”detachmentregion(rtarget <10cm).⇒ peakqtarget ~6.5MW/m2:Tediv andTidiv attheattachedregionbecamehigher.

Innertarget:ionizationstilloccursatTe =1-2eV.⇒ peakqtarget ~8MW/m2:surfacerecombinationloadisdominant.

Joint Special Design Team for Fusion DEMO

attachdetach

detach

qtargettot =6.5MWm-2qtargettot =8.3MWm-2

Ar seedinginPout =250MW,frad=0.75,i.e.increasingPout-Prad from50to62.5MWAr puffrateisdecreased(4to3x1020/s)⇒ Psep~240MWiscomparable,Praddiv =150MWislower

Largerqtarget (duetosurfacerecom.)isseenattheinnertarget?・ needimprovementofA&Mand/orelastic-collisionprocesses・ in-outasymmetryinpowerdistributionmayberequired.

3.EngineeringdesignforJADEMOdivertor

0.8m

0.8m

W-monoblock&Cu-alloypipeunits

W-monoblock&F82Hpipeunits

Heatsinkunitandcooling-piperoutinginacassettestructureareinvestigated:(1) Remotemaintenance:onecassettecovers7.5° toroidalarea⇒ 3cassettesarereplacedfrom1port(total16portsandTFCs)[Utoh,etalFED2015](2)Fuel/Heexhaust,pumpingroute⇒ privatepumping,openingatthebottom(tentative)(3)Powerexhaustdesignundern-irradiation⇒ ApplicationofITERtechnologyisinvestigated:

W-monoblock &Cu-alloycoolingpipe⇒ Cooling-pipearrangementinacassette⇒ Analysisoftheheatsinkof~10MWm-2(4)CassettedesignandReplacement

Joint Special Design Team for Fusion DEMO

•Neutronics analysis(MCNP-5codewithFENDL-2.1nucleardatabase)showsW-nonoblock &CuCrZr heatsinkcanbeappliedathighheatfluxandlown-fluxarea:~1dpa/fpy (inner)and~1.5dpa/fpy (outer)onCuCrZr pipenearthestrikepoints.

DesignconceptofWandCuCrZr/F82Hunitinneutroncondition

ITERtechnology(W/CuCrZr-target)canbeapplied(ITERlifetimedoseonW:0.54dpa,CuCrZr:2.5dpa),whilethereplacementis1-2yearsinDEMOcondition,duetoincreasingoperationtimeaswellastheneutronflux.

•HeatremovalconceptofW-monoblock &CuCrZr/F82H cooling-pipes wasdesignedforlargemargincaseonthetarget(Pdivthermal:380MW+Pdivneutron:118MW),wherePdivthermal is1.7timeslargerthanSONICsimulation(Pdivthermal =Psep – PradSOL =220MW).

Designconceptofthewater-coolingrouting(2015)

Asakura etal.Nucl.Fusion2017

•PressurizedwaterfortheCuCrZr-pipe:200°C,5Mpa,andfortheF82H-pipe:290°C,15MPa(similartopressurizedwaterreactor:PWR)isusedinthedifferentroutes.Note:PWRwaterwillbeusedfortheelectricgeneration

byturbinesystemsimilartoaPWR.

HeatanalysisinW-monoblock &CuCrZr-pipeheatsink•Base-Temp.(200 °C)ofthepressurizedwaterandNuclearheatlargerthanITER.•Heatloadprofiles(plasma,radiation,neutral) withthepeakheatload10MWm-2,areusedfor3DFEMcalculationofheatfluxandthermalstress.

•Max.temperaturesofW-surface1021°C (lowerthanrecrystalization Temp.1200°C),andCu-alloy-pipe331°C arewithinoperationrange.

+NuclearHeatTotalpeakheatload:10MWm-2

ABAQUS 3DFEManalysisofW/Cu-alloy(four)monoblock unit:

Joint Special Design Team for Fusion DEMO

HeattransportinWandCuCrZr pipe,andmax.heatflux•Max.heatfluxtocoolant:18MWm-2 is2/3oftheCriticalheatflux(27MWm-2).Heatfluxtocoolingpipeislocalizedatsidesurface:25MWm-2⇒ acceptablelevel

•ThermalstressisincreasedatupperinnersurfaceofCuCrZr-pipebyelasticanalysis:maximumstress-strainisevaluatedwithelasto-plasticstressanalysis,consideringresidualstress-strainafterthebrazeprocessfrom950°:notapparentin10MWm-3.

Joint Special Design Team for Fusion DEMO

Summary1:Powerexhaustanddivertor designforJADEMOPowerhandlingwithAr seedinghasbeeninvestigatedin steady-stateJADEMO:Pheat=Pa+Padd~435MW,Rp=8.5m,Psep~258MW,Psep/R~30MW/m,wherenAr/ne~0.6%.Theconceptwasrevisedtoincreasek95 from1.65to1.75(andincreaseIp),andtoimprovetheplasmaperformancefortheimpurityseeding(Pradmain/Pheat~0.4).

Joint Special Design Team for Fusion DEMO

(1)Divertor (largerthanITER)hasbeeninvestigatedusingSONICwithAr seeding.increasing PradSOL+div/Pheat =0.43 inlong-legdivertor (Lleg=1.6m)⇒ (nAr/ne)SOL=0.4-0.5%,Thepowerexhaustscenarioprovidespeak-qtarget isreducedlessthan10MWm-2⇒ ITERdivertor technology(W-monoblock&Cu-alloy pipe)isapplicable.

•Improvementofplasma&neutralmodellinginthedetachment,andthedivertoroperation(lowerfrad,c andD, geometry,impurityselection)arehighpriorityissues.

PhysicsissuesoftheJADEMOpowerexhaustdesign(atthisstage):•PossibilityanditsmarginofhighfGW inimpurityseeding(ne iswithinexp.database).•PthL-HandH-L anditsmargininZeff =2-3(andfGW >1).•Controlofradiationpeakanddetachfrontindivertor leg(leglength,powerflux?)•Scenario(model)oftheedgeplasmawhentheX-pointradiationisenhanced.•Appropriatec &DprofilesforDEMO,anddissipationinthedetachment(Sdiv).•Impurityconcentration(nimp/ne) atedge-SOL–divertor,andtheshieldingefficiency.

Summary2:Powerexhaustanddivertor designforJADEMOJoint Special Design Team for Fusion DEMO

(2)HeatremovalofW-monoblock/cooling-pipeandwater-coolingarrangementinacassettewerestudiedforseverecase(Pdivthermal:300MW+Pdivneutron: 128MW):

•Neutronics analysisshowedW/CuCrZr heatsinkcanbeappliedathighheatfluxandlown-fluxarea⇒ frequentremote-maintenance(1-2year)willberequired.

•3DheattransportanalysisshowedMax.temp.onW(1021°C)andCu-alloy(331°C)andHeatfluxwereinoperationrange:appropriateforpeakqtarget = 10MWm-2-level.

•Cassettedesign,consideringnucl.heatcooling,n-shield,exhaustopeningandtargetunitreplacement,ishighpriorityissuein2016-2017.

EngineeringandmaterialissuesoftheJADEMOdivertordesign(atthisstage):•ApplicationofCuCrZr athighirradiationdose(>2dpa)asaheatsink(structure)•Appropriatewatertemperature(150-200C)forW/Cu-alloyheatexhaustunit.•EvaluationofRMperiod(lifetime)evenwithoutmelting:erosion,re-crystallizationofbothWandCuCrZr andthermalfatiguebytransientevents.

•ReplacementdesignofCuCrZr coolingunitinthecassette(inhotcell)•Divertor cassettedesignasaneutronshieldforthevacuumvessel.