Aneutronics–thermalhydraulicsmodelforpreliminarystudiesonTRADEdynamicsOriginalResearchArticle

Inthelastfewyearsthepossibleroleofacceleratordriversystems(ADS)foreffectivetransmutationstrategieswithfullyclosedcycleshasreceivedincreasedattentionduetotheirpotentialtoimprovetheflexibilityandsafetycharacteristicsoftransmutationsystems.ThesubstantialdifferencebetweentheneutronkineticsanddynamicbehaviorofADSandconventionalcriticalreactorshasgivenrisetoawideinternationalconsensusontheneedofanexperimentalprogramtoimprovetheirknowledgeandtovalidatecalculationmethods.TothisendtheinternationalcooperationTRADEproposedasub-criticalexperimentbasedonthecouplingofaTRIGAreactorinsub-criticalcoreconfigurationwithaprotonaccelerator(cyclotron)bymeansofaneutronspallationtarget.TheexperimentwasinitiallyconceivedintheRC1-TRIGAreactorlocatedattheENEACenterofCASACCIA(Rome,Italy)todemonstratethefeasibilityoftheacceleratordrivensystem(ADS)conceptatarepresentativepower.ThisarticlepresentsapreliminarystudyperformedwiththeRELAP5/PARCScodeonthedynamicbehaviorofsuchasysteminordertodemonstratethecodecapabilitytosupportthedesignoftheexperimentandthesafetyanalysis.ThespecificcodeversionusedjoinsthewellknowncapabilityofRELAP5totreatlightwaterreactorswiththepotentialityofPARCSmodifiedbyENEAtosimulatethethree-dimensionalneutronicsofsub-criticalsystems,i.e.totreatexternalneutronsources.PARCSmodificationsarepreliminaryassessedagainstasimpleanalyticalsolutionofthesub-criticalneutronicsoftheexperimentbasedonthekineticspseudo-potentialsmethod.Aquitedetailedmodelforthecoupledcodeisdevelopedinordertorealisticallyevaluateboththethermalfeedbackeffects,thecontrolrodactionandtheexternalsourcestrengthchanges.Awiderangeofoperationalandaccidentaltransientsofthesub-criticalreactoraresimulatedwiththecoupledmodelinordertoobtainafirstsystemresponsetoanumberofreactorelementaryeventsatdifferentsubcriticalitylevels.Thecalculationresultsshowahighqualitativeagreementwiththesub-criticalsystemphysicaltheoryunderlininghowthenumericalmodeldevelopedcouldbeausefultoolforthedefinitionoftheoperationalproceduresandtheinvestigationofaccidentalconditions;moreovertheaccidentaltransienttrendshighlighttheinherentsafetybehavioroftheTRIGAresearchreactorsthatmakesthemextremelysuitableforthecouplingofthedifferentcomponentswithaquitesimplelicensingprocedures.