ContentslistsavailableatScienceDirect
Fusion
Engineering
and
Design
j ourna l h o m e pa g e :w w w . e l s e v i e r . c o m / l o c a t e / f u s e n g d e s
Post-test
analyses
of
LIFUS5
Test#3
experiment
Marica
Eboli
a,∗,
Alessandro
Del
Nevo
b,
Nicola
Forgione
a,
Maria
Teresa
Porfiri
caDICI,UniversityofPisa,LargoLucioLazzarino2,56122Pisa,Italy
bENEAFSN-ING-PAN,C.R.Brasimone,Camugnano,Bologna40032,Italy
cENEAFSN-FUSTEC-TEN,viaE.Fermi45,Frascati,00044,Italy
h
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g
h
l
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g
h
t
s
•PreliminarycodeassessmentprocessofSIMMER-IIIforfusionapplication.
•LIFUS5Test#3post-testanalysesperformed.
•Improvedknowledgeoftheexperimentandexecutionprocedures.
•RelevanceofcorrectI&BconditionsonthepredictivecapabilitiesofSIMMERcode.
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Articlehistory:
Received1October2016
Receivedinrevisedform4February2017
Accepted10March2017
Availableonline22March2017
Keywords: Water Lithium–lead SIMMER Chemicalreaction WCLLbreedingblanket Safety
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Theinteractionbetweenlithium-leadandwaterisamajorconcernofWaterCooledLithiumLead(WCLL) breedingblanketdesignconcept,thereforedeterministicsafetyanalysisofthein-boxLOCApostulated accidentisofprimaryimportance.Thepaperpresentsthepreliminarycodeassessmentprocessofthe modifiedversionofSIMMER-IIIcodeforfusionapplicationbymeansofLIFUS5Test#3post-test anal-yses.Aseriesofsensitivitycalculationsareperformedtoovercomeuncertaintiesinthetestdataand experimentexecution,andtoinvestigatethecapabilityofthecodeinpredictingthephenomena occur-ringduringPbLi/waterinteraction.Resultsshowagreementbetweennumericalresultsandexperimental data.Besides,differencesareobservedinthefirstsecondofthetransientduetoimperfectknowledgeof initialandboundaryconditions,andtestexecutionprocedure.
©2017TheAuthors.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction
Thesafetyissuesconnectedwiththelithium-lead/water inter-action in WCLL breedingblanket [1] is a potential hazard that shallbe considered.Therefore, the availability of qualified sys-temcodefordeterministicsafetyanalysisofin-boxLOCA(Lossof CoolantAccident)isofprimaryimportance.Themodifiedversion ofSIMMER-IIIcodeforfusionapplication,whichimplementsthe PbLi/waterchemicalreaction,hasbeendevelopedbyUniversityof PisaandENEACRBrasimone[2]andcurrentlyisundervalidation process.
Theaimofthepaperistodescribethepreliminarycode assess-ment of SIMMER-III Ver. 3FMod.0.1 code by means of LIFUS5 Test#3 post-test analyses. To address this objective, Section 2
brieflydescribestheTest#3experiment,thenthenodalizationof
∗ Correspondingauthor.
E-mailaddress:marica.eboli@for.unipi.it(M.Eboli).
thefacilityisreportedinSection3.Post-testanalysesresultsare illustratedinSection4,inwhichconsiderationsaboutthe compre-hensionofexperimentaldataarediscussed.Finally,conclusionsare reportedinthefinalsection.
2. DescriptionofLIFUS5Test#3
2.1. Facilitydescription
LIFUS5[3,4]wasdesignedandoperatedatENEACRBrasimone toexperimentallyinvestigatetheconsequenceofLOCAaccidents inliquidmetalpools.Fig.1showstheProcessand Instrumenta-tionDiagram(P&ID)ofthefacility,descriptedindetailinliterature
[3,4].ThereactionvesselS1containedamock-upofUshaped cool-ingtubes,asforeseeninpreviousdesignofWCLLBBforDEMO[5]. ThewaterinjectiondevicewasplacedinthebottomofS1belowthe tubebanksectorandhadanorificediameterof4mm.Several pres-suretransducersandthermocoupleswereplacedbothinS1andin theexpansionvesselS5tofollowthepressureandtemperature evolutionduringtheinteraction.
http://dx.doi.org/10.1016/j.fusengdes.2017.03.046
0920-3796/©2017TheAuthors.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBY-NC-NDlicense(
Fig.1.P&IDofLIFUS5facility.
Table1
Test#3operatingconditions.
Parameter Test#3
PbLitemperature 330◦C
Waterinjectionpressure 155bar
Watertemperature 295◦C
Sub-cooling 50◦C
FreevolumeinS5 5l
Timeofinjection 6s
2.2. Test#3conditions
Beforetheexecutionofthetest,vacuumwasgeneratedbetween thevalveV14andthewaterinjector.Atthestartofthetest,valve V14openedandhotpressurizedwaterwasdischargedfromthe watertankS2toS1throughtheinjectionline.Thewaterinjection pressurewasfixedat155barandkeptconstantthroughaconstant pressurizationofthevesselS2.After6s,theinjectionwas inter-ruptedclosingthevalve.ThemainoperatingconditionsofTest#3 aresummarizedinTable1.
2.3. Openissues
TheexperimentalresultsdescribedinRef.[3]arenotexhaustive. Moreover,onthebasisofthereviewofavailabledocuments,the executionoftheexperimentisaffectedbyuncertaindatainrelation to:
• Layoutoftheinjectordeviceand relativepositioninrespectto theU-tubemock-up.Nogeometricaldrawingsordimensional informationwasfoundinliterature(Refs.[3,4]).
• Injectedmassofwater,becausenomassflowmeterwasinstalled intheinjectionline.Inliterature,thisvaluewasreportedas1.3kg
([3,4])butnoaccuracyisreportedaswellasnoreferenceon theprocedureusedfortheevaluation.Thisvalueisconsidered unreliable.
• Layoutoftheexpansion tubes.Nodocumentwasfoundforthe configurationoftheexpansiontubesanda3 pipeconnecting S1andS5,butonlytheexpansiontubesmaindimensionsare available(Refs.[3,4]).
3. LIFUS5nodalizationbySIMMER-III
ThenodalizationofLIFUS5bySIMMER-IIIVer.3FMod.0.1code (theversionforfusionapplicationwhichimplementsPbLi/water chemicalreaction)[1]isdevelopedin2Daxisymmetricgeometry, despitethelimitationofrepresentingtheasymmetriesofLIFUS5 facility.Itisconstitutedby5mainparts(Fig.2)representing: • thewatertankS2andtheS2-S1pipeline,
• theinjectordeviceanditsorifice,
• thereactionvesselS1,theU-tubemock-upandtwoplates divid-ingS1intofoursectors,
• theS1-S5linkwhichpreservestheflowareaoftheexpansion tubes,
• theexpansionvesselS5.
Thegeometricaldomainissubdividedinto17radialand28axial meshcells.Theoverallvolumeofthemodelisobtainedrotatingthe 2DSIMMERdomainalongtheaxisofsymmetry.Colorsdistinguish thedifferentfluids:PbLirepresentedinred,waterinblue,covergas (andthehydrogenproducedbythereaction)inwhite.Itisworth tounderlinethatthisnodalizationconsideredasfirstattemptto validatetheSIMMER-IIIcodeforfusionapplicationisthesameof pastnumericalactivities,reportedinRef.[4].
Fig.2.LIFUS5facilitynodalizationbySIMMER-III.
TheboundaryconditionsareappliedinS2covergascellsto reproducethecontinuousinflowofArgonfromthecylinder,at theconstantpressureof155bar.Theinitialconditionsofpressure andtemperatureinS1,S5,andintheinjectionline,areset coher-entlywiththedatareportedinTable1.Thereferencerunisset openingthevirtualwall,whichrepresentthevalveV14att=0s, anditismaintainedopenfor6s,coherentlywiththeexperimental specifications.Theamountofwaterinjectedisnotimposed,but cal-culatedbySIMMER-IIIaccordinglytopressuredifferencebetween theinjectorinletandthereactionvessel.
4. Analysisofpost-testcalculationresults
Three-stepanalysisispursuedasapartofthecodeassessment process.Theinitialconditionresultsattheinjectiontimeare rele-vantforthecharacterizationofthethermal-hydraulicconditionsat thebeginningoftheexperiment.Thereferencecalculation“Run0” isnotthebestcalculationbecauseitisbasedonaformer anal-ysisset-uprunningthecodewithoutthechemicalimplemented model[4].Sensitivityanalysesarecarriedouttodemonstratethe robustnessofthecalculation,tocharacterizethereasonsfor pos-siblediscrepanciesbetweenmeasuredandcalculatedtrendsthat appearinthereferencecalculation,tooptimizecoderesultsand useroptionchoices,toimprovetheunderstandingofexperimental data,andtoimprovetheknowledgeofthecodebytheuser. 4.1. Referencecalculationresults
Thepressuretransientcanbedividedintothreecharacteristic phasesofinteraction[3],alreadyrecognizedinBLAST experimen-talcampaign[6]. Twoadditionalphases (Phase0 and Phase4) arediscussedaspartofthecalculationsetup.Thenumericaland experimentalpressuretrendsarereportedinFigs.3and4,while
Fig.5showsthewatermassflowrateandthehydrogengeneration calculatedbythecode.
4.1.1. Phase0[onsetofvalveopening–0ms]:waterinjection linepressurization
AssoonasvalveV14opens,waterstartstoflowandto pressur-izethepipelineupstreamtheinjectioncap.Thedesignofthetest specifiesthatthecapshouldberupturedatthereferencepressure (i.e.155bar).Thisimpliesthatsubcooledwaterat295◦Cwillenter inS1.Duringthisphase,nomeasuredexperimentaldatumis avail-able.Therefore,accordingwiththesetupreferencecalculation,the startofthetransient(t=0s)issupposedtobethetimeofthe injec-tioncapbreaking.Thesimulationassumesthatsubcooledwaterat thedesigntestconditionsisinjecteddirectlyinthereactionvessel S1.
4.1.2. Phase1[0s–200ms]:coolantflashingandS1 pressurization
ThewaterinjectionandflashinginS1causesasuddensteep pressurization.Thecoderesultsevidenceafasterpressureincrease. Thecalculatedpressurepeakis127baroccurringatabout20ms, whereas theexperimental valueis 100barat 200ms. Different causesareidentifiedforjustifyingthesetrends.However, consid-eringthedataofTest#6[7]wherethepressurewasmeasuredin theinjectionline,themostlikelyjustificationisanearlyruptureof theinjectioncapwhichmaycausetwophaseflowconditionsatthe orificeintheexperiment,resultinginaslowerpressurization.This deviationfromthetestspecificationwillbeanalyzedinsect.4.2. Thecalculatedamountofwaterinjectedduringthisphaseis1.58g, whichresultsfromasuddenspikeofmassflowrateat0.79kg/s. 4.1.3. Phase2[200ms–800ms]:S5pressurization
Thephasestartswiththecriticalflowalmostconstantatabout 0.45kg/s.Nomeasurementisavailableforcomparison.The calcu-latedpressureinthereactionvesselslightlydecreasesandthen stabilizesatabout115–120bar,whichcorrespondsatthe satura-tiontemperatureofabout325◦C.Thesimulationcalculates this phaselongerthanintheexperiment.Thiscanbeexplainedwith alowerexpansionvolumeinS5(itisnotclearlystatedhowthe levelismeasured,anditsaccuracy)andalargersteamflow mov-ingfromS1toS5.Apressurepeakof28barisalsomeasuredin theexpansionvesselat377ms,followingasuddensteeppressure increase,whichseemsconnectedtoasortofCCFLoccurrenceinthe expansionpipe.Indeed,vaporgas,risinginthepipe,expandsinS5 becausethedifferentialpressureandasconsequenceofthedrag betweenthefluidsmaycausetheformationofaplugofPbLiacting astemporarypistonand,thus,compressingthesteamofS5,which cannotcondensebecausethelowabsolutepressure.Thisprocess inthesimulationoccursat600ms.However,SIMMER-III overes-timatestheamountofPbLitransportedinS5andtheexpansion vesselisalmostsolid,causingpressureoscillationsatthebeginning ofphase3.Thesimulationpredictsalinearhydrogengenerationof about67.7g/s,upto660mswhenthepressuresareequalizedand theinjectedwatermassflowratestartstodecrease.
4.1.4. Phase3[800ms–6500ms]:S1andS5pressuresequilibrium OnceS1andS5pressuresareequalizedintheexperiment,they increaseuptothemaximumpressureof150bar,occurringwhen thewaterinjectionisstopped.Thepressureincreaseisdrivenby thewaterinjected,whichevaporates,after3300ms,inthezone wherethechemicalreactionaffectsthemelttemperatureabove thesaturationvalue.Thesimulationpredictspressureoscillations at beginning ofthe phase 3 in S5and a fast pressure increase upto155bar,reachedat1000ms.Oncethispressureisreached, theinjectionstops.Fromthistime on,thehydrogengeneration becomesnegligible. Thecodepredictsanoverall injectedwater
0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 0.0 2.0 4.0 6.0 8.0 10.0 Pressure [bar] Time [s]
EXP_PT4 Run0_PK[S1] Run7_PK[S1]
EXP_PT1 Run0_PK[S5] Run7_PK[S5]
Phase 3
Phase 2
Phase 1
Fig.3. Run7vsRun0:pressuretrendsPK[S1]andPK[S5]andcomparisonwithexperimentaldata(PT4inS1andPT1inS5).
0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 Pressure [bar] Time [s]
EXP_PT4 Run0_PK[S1] Run7_PK[S1]
EXP_PT1 Run0_PK[S5] Run7_PK[S5]
Phase 3 Phase 2
Phase 1
Fig.4.Run7vsRun0:pressuretrendsPK[S1]andPK[S5]andcomparisonwithexperimentaldata.Zoomon0–2s.
massequalto0.367kg,whichresultmuchlowerthanthevalue reportedinthedescriptiondocument[3].
4.1.5. Phase4[6500ms–EoT]:systempressurestabilization Duringthisphasetheinjectionvalveisclosedandthe param-eters arestabilized. Thepressuresare almostconstant (slightly decreasing)intheexperimentandinthesimulation.
Finally, some considerations about the overall water mass injectedandchemicalreactionarereported:
• Watermassinjected.Literature[3]reportsthattheoverallwater massinjectedinthesystemis1.3kg.Thisvalueisunreliable. ConsideringthevolumesofS5andtheinjectionline,and assum-ingthatallthewaterevaporates,thecalculatedwaterneededto reach155barinsaturatedconditionsis0.350kg.Assumingthat thiswaterreactswithPbLiproducingH2,theoverallpressure shouldbebetween100.8barand201.5bar,dependinguponthe chemicalreactionprevailing.Itcanbeconcludedthatthe
over-allwaterinjectedinthesystemshouldbelargerthan0.262kg andlowerthan0.525kg.SIMMER-IIIcodeestimatesareasonable valuebeing0.367kg.
• Hydrogen generation. Considering the same assumption, the expectedmassofhydrogengeneratedshallbebetween20.4g and40.8g.Theresultsofthesimulationis,therefore,acceptable being31.1g.
4.2. Sensitivitycalculations
Considering the reference calculation (Run0), tens of sensi-tivity analyses were carried out to understand the reasons of discrepanciesbetweenexperimentalandnumericalresults,fully documentedin[7].
Inalltheruns,itwassupposedtoinjectsubcooledwater. Nev-ertheless,aftertherevisionofTest#6[7],thisconditionseemsto notreflecttherealexecutionoftheexperimentbecauseofanearly ruptureofthecapandtheconsequentlytwo-phaseflowinjection.
0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.045 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 H2production [kg] Mass flow rate [kg/s] Time[s] Run0_M[inj] Run7_M[inj]
Run0_H2(TOT) Run7_H2(TOT)
Fig.5. Run7vsRun0:massflowrateofinjectedwater(M[inj])andcalculatedhydrogengeneration(H2TOT).
Therefore,Run7wasperformedimposinga postulatedpressure transientfromvacuumto155barattheinjectiondevice,andthe earlyinjectorbreaksat53bar.Thesensitivityresultsareshown fromFigs. 3to5.It canbenoted howthepressuretransientis moresimilartotheexperimentaltrend.Itmightbesaidthatthe SIMMER-IIIcodesimulationisaffectedbythecorrectknowledge oftheboundaryconditions.InTest#3,theseconditionsresulting fromexperimentalevidencesarenotavailableandcanbetaken onlyformtestspecifications.
5. Conclusions
Theanalysesof Test#3 experiment gave thefollowing main results:
• The capability of SIMMER-III code for fusion application in predictingphenomenaconnectedwithPbLi/waterinteraction, consideringalsothechemicalreactionandhydrogenproduction, hasbeendemonstratedwithsatisfactoryresults;
• Thepost-testanalysespermitstoimprovetheknowledgeofthe experiments,i.e.thewatermassinjectedinthesystem,the injec-tionpressuretrend,andthepressureoftheinjectioncaprupture; • Thesensitivity analysespointed out therelevance of the ini-tial and boundary conditions on the predictive capabilities of SIMMER-III code to simulate phenomena connected with lithium-lead/waterinteraction.
Futureperspectiveistocontinuethevalidationprocessofthe modified SIMMER-III code by means of the next LIFUS5/Mod3 experimentalcampaigninordertoobtainreliableandreproducible experimentaldatawithwell-knownI&Bconditions.
Acknowledgments
This work has been carried out within the framework of theEUROfusionConsortium and hasreceivedfundingfromthe Euratomresearchandtrainingprogramme2014-2018undergrant agreementNo633053.Theviewsandopinionsexpressedherein donotnecessarilyreflectthoseoftheEuropeanCommission.
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