Neutrontransportbenchmarkexampleswithweb-basedAGENTOriginalResearchArticle

TheAGENT(ArbitraryGEometryNeutronTransport)anopen-architecturereactormodelingtoolisdeterministicneutrontransportcodefortwo-orthree-dimensionalheterogeneousneutronicdesignandanalysisofthewholereactorcoresregardlessofgeometrytypesandmaterialconfigurations.TheAGENTneutrontransportmethodologyisapplicabletoallgenerationsofnuclearpowerandresearchreactors.Itcombinesthreetheories:(1)mathematicaltheoryofR-functionsthatisusedtogeneraterealthree-dimensionalgeometriesofsquareorhexagonalheterogeneousgeometries,(2)thex–ymethodofcharacteristics(MOC)usedtosolveisotropicneutrontransportinnon-homogenized2Dreactorslices,and(3)theone-dimensionaldiffusiontheoryorMOCtheoryusedtocouplethex–yandzneutrontracksthroughthetransverseleakageandangularmesh-wisefluxvalues.TheR-functiongeometricalmoduleallowsasequentialbuildingofthelayersofgeometryandautomaticsubmeshingbasedonthenetworkofgeometricdomainfunctions.ThesimplicityofgeometrydescriptionandselectionofparametersforaccuratetreatmentofneutronpropagationisachievedthroughtheBooleanalgebraichierarchicallyorganizedsimpleprimitivesintocomplexdomains(bothbeingrepresentedwithcorrespondingdomainfunctions).AGENTmethodologiesandnumericalsolutionsareapplicableinvalidatingneutronicanalysisforGenIVreactordesignswhiletheeffectofdoubleheterogeneityinveryhightemperaturereactors(VHTRs)isunderdevelopment.TheaccuracyiscomparabletoMonteCarlocodesandisobtainedbyfollowingneutronpropagationthroughrealgeometricaldomainsthatdoesnotrequirehomogenizationorsimplifications.Theefficiencyismaintainedthroughsetofaccelerationtechniquesintroducedatallimportantcalculationlevels.Thefluxsolutionincorporatespoweriterationwithtwodifferentaccelerationtechniques:coarsemeshrebalancing(CMR)andcoarsemeshfinitedifference(CMFD).Thestand-aloneoriginallydevelopedgraphicaluserinterfaceoftheAGENTcodedesignenvironmentallowstheusertoviewandverifyinputdatabydisplayingthegeometryandmaterialallocation.Theusercanalsoviewtheoutputdatasuchasthree-dimensionalmapsoftheenergy-dependentmesh-wisescalarflux,reactionratesandpowerpeakingfactors.TheAGENTcodeisinaprocessofanextensiveandrigoroustestingforvariousreactortypesthroughtheevaluationofitsperformance(abilitytomodelanyreactorgeometrytype),accuracy(incomparisonwithMonteCarloresultsandotherdeterministicsolutionsorexperimentaldata)andefficiency(computationalspeedthatisdirectlydeterminedbythemathematicalandnumericalsolutiontotheraytracinganditerativeapproachofthefluxconvergence).ThispaperoutlinesmainaspectsofthetheoriesunifiedintotheAGENTcodeformalismanddemonstratesthecodeperformance,accuracyandefficiencyusingfewrepresentativeexamples.TheAGENTcodeisamainpartofthevirtualreactorsystemdevelopedfornumericalsimulationsofresearchreactors.Fewillustrativeexamplesofthewebinterfacearebrieflyoutlined.