AnalysisoftheEuropeanresultsontheHTTR’scorephysicsbenchmarksOriginalResearchArticle

IntheframeoftheEuropeancontractHTR-N,aworkpackageisdevotedtothecodevalidationandmethodimprovementsasfarasthehightemperaturegas-cooledreactor(HTGR)coremodellingisconcerned.Institutionsfromthreecountriesareinvolvedinthisworkpackage:FZJinGermany,NRGandIRIintheNetherlands,andCEAinFrance.ThepresentworkisbasedonabenchmarkproblemproposedbyJAERIthroughtheIAEA.ItconcernstheHTTR’sstart-upcorephysicsexperimentsthatwereagoodopportunityfortheEuropeanpartnerstovalidatetheircalculationaltoolsandmethods.Thenumberoffuelcolumnsnecessarytoachievethefirstcriticalityandtheexcessreactivityfor18,24,and30fuelcolumnsinthecorehadtobeevaluated.Pre-testandpost-testcalculationalresults,obtainedbythepartners,arecomparedwitheachotherandwiththeexperiment.Partsofthediscrepanciesbetweenexperimentandpre-testpredictionsareanalysedandtackledbydifferenttreatments.InthecaseoftheMonteCarlocodeTRIPOLI4,usedbyCEA,thediscrepancybetweenmeasurementandcalculationatthefirstcriticalityisreducedtoΔk/k∼0.85%,whenconsideringthereviseddataoftheHTTRbenchmark[Fujimoto,privatecommunication].Inthecaseofthediffusioncodes,thisdiscrepancyisreducedtoΔk/k∼0.8%(FZJ)and2.7or1.8%(CEA).