FluidRadioactivityConcentrationforth26GLXVv24.docx

FluidRadioactivityConcentrationforth26GLXVv24.docx

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FluidRadioactivityConcentrationforth26GLXVv24

FluidRadioactivityConcentration

fortheITERTokamakCoolingWaterSystem

ITER_D_26GLXVv2.4

Abstract

Thisdocumentsummarisesthedataforthefluidradioactivityconcentration,neededfortheclassificationofthevariousITERcomponentsinaccordancewithFrenchorderdated12thDecember2005concerningnuclearpressureequipment.

ITER_D_26GVLXv2.4

Date:

04/01/2010

Name

Affiliation

Author

V.Barabash

P.Cortes

MaterialsandStandardOfficer,CIE/TI/SYSA

SectionLeader,CIE/NSE/SAA

Reviewed

M.Iseli

M.Loughlin

E.Polunovskiy

W.Curd

CIE/NSE/SAA

CIE/TI/SYSA

CIE/TI/SYSA

SectionLeader,CEP/PED/CWS

Approvedby

N.Taylor

DivisionHead,CIE/NSE

TableofContent

1Introduction3

2Sourcesofradioactivity4

3Tritiuminventoryincoolantsystems4

3.1Tritiumincoolantfrompermeation4

3.2TritiuminVacuumVesselcoolantfromboratedsteel5

414CproductioninITERwatercoolant6

5Activatedcorrosionproducts6

5.1VacuumVesselPHTS7

5.2FirstWallBlanketPHTS8

5.3DivertorPHTS9

5.4NeutralBeamInjectionSystemandNBPHTS10

5.5Proposeddesignguidelinevalues10

6Wateractivation11

7Summaryandrecommendation13

8Appendix115

9References17

1Introduction

FrenchOrderdated12thDecember2005concerningnuclearpressureequipment,Arrêtédu12décembre2005relatifauxéquipementssouspressionnucléaires,（ESPN）,[Ref.]definesnuclearpressureequipmentsuchas:

-IsdefinedbyI,Article2oftheDecreedated13December1999,exceptingequipmentspecifiedinpointsator,II,Article2;

-IsusedorintendedtobeusedinabasicnuclearfacilityotherthanthosespecifiedinArticle17oftheDecreedated11December1963amended;

-Directlyensure,undertheconditionsdefinedforoperationalpurposes,thecontainmentofradioactivesubstances;

-Leadtoradioactivereleasesgreaterthan370MBqintheeventoffailureasevaluatedasspecifiedhereafter.

Thereleaseofradioactivityasmentionedinthefourthbulletitemaboveisevaluatedasfollows:

-Forvessels,theproductofitsvolumemultipliedbytheactivityconcentrationofthefluidcontainedinsaidequipment,calculatedasthesumoftheactivityconcentrationduetoallelementscontainedwithinexceptingtritium,nitrogen-13,oxygen-15&19,fluor-20,21&22;neon-19&23,whicharemultipliedbyacoefficient1/1000.

InaccordancewithArticle3ofESPN[Ref.1]:

Nuclearpressureequipmentisclassifiedintothreecategories,fromN1toN3,inrelationtothesignificanceoftheradioactiveemissionspossiblyresultingfromtheirfailure.

a）TheN1categoryappliestoallnuclearpressureequipmentforwhichfailuremayleadtoconditionsunderwhichthesafetyreportandrelateddocumentationgoverningthebasicnuclearfacilitywheresaidequipmentislocatedordestinedtobelocateddonotprovidemeasuresmakingitpossibletobringthefacilitybacktoasafestate,

b）TheN2categoryappliestoallnuclearpressureequipmentthatisnotclassifiedintheN1categoryandforwhichthefailuremayresultinradioactivereleasesgreaterthan370GBqevaluatedasindicatedinIIofArticle2.

c）TheN3categoryappliestoallnuclearpressureequipmentthatisnotclassifiedintheN1orN2categories.

ASNGuide[Ref.],includesthefollowingstatement:

Theactivitylevelconsideredfortheclassificationofnuclearpressureequipmentcorrespondsstrictlytotheactivityofthefluidcontainedundernormalserviceconditions.

InaccordancewithESPN,Article5,theoperatorofabasicnuclearfacilitymustcompilealistofnuclearpressureequipmentusedinthefacility.Theoperatormustdetermineandjustifythelevelandcategorythataregiventoeachpieceofequipment.ThislistandrelatedjustificationsaretobemadeavailabletotheRegulatoryBodyinFrance（currentlyASN,AutoritédeSurêtéNucléaire）,andpersonnelinchargeofmonitoringpressureequipment

ThisdocumentsummarisestheavailabledatafortheradioactivityconcentrationinthetokamakwatercoolingsystemintheITERandproposesthereferencevaluesofactivityconcentration,whichshallbeusedfortheclassificationoftheITERcomponentsinaccordancewithESPN.

2Sourcesofradioactivity

TheITERcomponentsarecooledbypressurisedwater.Thecoolingwatersystem（CWS）consistsofthetokamakcoolingwatersystem（TCWS）,thecomponentcoolingwatersystem（CCWS）,thechilledwatersystem（CHWS）,andtheheatrejectionsystem（HRS）.

TheTCWSconsistsoftheprimaryheattransfersystems（PHTSs）andthesupportingsystems,thechemicalandvolumecontrolsystems（CVCSs）,thedrainingandrefillingsystems,andthedryingsystem.TherearethreePHTSloopsfortheFirstWallBlanket,oneforthedivertorandlimiter,onefortheNeutralBeamInjector,andtwoforthevacuumvessel.

Themainsourcesofradioactivityinfluid（water）,whichshallbetakenintoaccountinaccordancewithESPNrequirements,are:

-Tritium,whichpenetratethroughthecooledmetallicmaterialsduetodiffusionmechanism,

-Tritium,generatedduringneutronirradiationinboratedsteelinvacuumvesselshell,anddiffusedinwaterfromthematerial,

-14Cisotopeproducedthroughneutronactivationoftwoisotopesofoxygeninwater,

-SuspendedActivatedCorrosionProductsinthewaterofthevarioussystemsoftheTokamakCoolingWaterSystem（TCWS）,

-16Nand17Nisotopesgeneratedbyhighenergyneutronsviathe16O（n,p）16Nand17O（n,p）17Nreactions.

ItshouldbenotedthattheresultsofcalculationofradioactivityconcentrationintheITERcomponentsdependsonmanyparameterssuchasanticipatedoperationalscenarios,detaileddesignofthecomponents,appliedcodeassumptions（1-D,2-Dmodelgeometry,activatedenergyfordiffusion,etc.）.

Notethattheactivityconcentrationinthesecoolingloopswouldbuildupslowly（except16Nand17N）.Somecomponents（e.g.divertor）willbeexchangedduringoperationandtheactivityinfluiddependsonprocedureofdraininganddryingofthecomponent.

TheultimategoalvaluesofradioactivityconcentrationsforvariouscomponentshavetobeestablishedbeforehandandthentheoperationoftheITERcanbeterminatedincaseofexceedingthelimits.

3Tritiuminventoryincoolantsystems

3.1Tritiumincoolantfrompermeation

GSSR,[Ref.],includestheassessmentofthetritiuminventoryintheITERwatercooledsystem.

Diffusionofimplantedtritiumintotheprimaryfirstwall,baffle,anddivertorduringoperationandbakingwillresultintritiumcontaminationofthecoolingwaterofthosecomponents.Theanalysisstepsoftheseprocessesincludetheimplantationinventoryanalysis,thepermeationthroughthematerial（basedondiffusivity）,andfinallythetritiumbalanceinthewater.

Tritiumpermeationisdominatedbythephasesofbakingwhenthein-vesselcomponentsareattheelevatedtemperaturesof240ºC.Theaveragetotaltritiumpermeationintocoolingloopshasbeenestimatedas0.7gperFWcoolingloop[Ref.]bytheendofplasmaoperationwithanaccumulatedfluenceof0.5MWa/m2in10years.Thebakingtimehasbeenestimatedasthreemonthperyear.Themaincontributoristhebredtritium,whichbuildsupalsoneartheberyllium/Cualloyinterface（ITERfirstwall）andisconservativelyassumedtobepartiallymobilisedduringbaking.Withoutthiseffect,tritiumpermeationthroughberylliumshowsabreakthroughbehaviourandverylittleisexpectedduringITERoperation.Amorediffusioncontrolledpermeation（weaktrapping）wouldleadtoaveryslowbuildupofthetritiumconcentration

Thevalueforvacuumvesselandvacuumvesselcoolingsystemhasbeencalculatedin[Ref.]andrangesfrom0upto47mili-gor0.0003gT/m3withtheveryconservativeassumptionofnotritiumtrapping,therefore0.0001gT/m3havebeenassumedasadministrativeguideline.Generallylowpermeationmeanshighertritiuminventoryinthesteelstructureandviceversa.

Thereisnospecificcalculationforthedivertorwatercoolingsystem.Divertorisexchangeablecomponent.Onlylastdivertorwillbesubjectedtosignificant（~0.2MW*a/m2）neutronfluence.

Becauseofnotritiumbreeding,smalldiffusioncoefficientsforhydrogeninCFCandW,andthesmallersurfaceareanoorlittletritiumpermeationisexpectedforthedivertorcomparedtotheBe-FW.Possiblepermeationinthecassetteregionisnotconsidered.ConservativelythesametritiumconcentrationasintheFWloopisassumedforthedivertorcoolingsystem.

ForNeutralBeamInjectionsystemthesametritiumconcentrationasintheFWloopisassumed.Thisvalueisconservativealso,becausewatertemperatureislowerincomparisonwithwatertemperaturefortheFirstWall.

Table1liststheresultingguidelinesforthemaximumtritiumconcentrationintheprimarycoolantwaterofITERcoolingloopsbypermeation.

Table1:

Tritiumconcentrationinprimarycoolingwaterbypermeation[Ref.3].

Vacuumvesselcoolingsystem

<0.0001gT/m3water（0.001Ci/kg）

~36GBq/m3*

In-vesselcomponentscoolingsystem

<0.005gT/m3water（0.05Ci/kg）

~1800GBq/m3*

*Note:

ForESPNclassificationthesevaluesshallbeusedwithcoefficient1/1000.

Theuncertaintiesinthephysicalpropertiesforsurfaceprocessrates（includingad-anddesorption）anddiffusioncoefficients（dependentonimpurities,latticedefects,latticediffusion,grainboundarydiffusion,irradiationandsurfaceeffectsetc.）,togetherwiththeirexponentialdependenceontemperatureandthespecialoperational,chemicalandgeometricaleffectssuchashotspots,cracks,bracedinterfaces,makeitverydifficulttoestimateuncertainties.Theperformedcalculationsareb