Quantitativeassessmentofthermal–hydrauliccodesusedforheavywaterreactorcalculationsOriginalResearchArticle

TheRD-14MlargeLOCAtest,characterizedbyareliablesetofexperimentaldata,wasselectedforaninternationalstandardproblemexercise(SPE)entitled“Intercomparisonandvalidationofcomputercodesforthermal–hydraulicssafetyanalyses”.TheactivitywasperformedwithintheframeofInternationalAtomicEnergyAgencyʹs(IAEAs)TechnicalWorkingGrouponAdvancedTechnologiesforHeavyWaterReactors(TWG-HWR).Inthisstudy,therecentlyimprovedfastFouriertransformbasedmethod(FFTBM)wasusedforaccuracyquantificationofRD-14MlargeLOCAtestB9401calculationsofsixparticipantsusingfourdifferentthermal–hydrauliccodes.Inaddition,developingthecapabilitytocalculatetheaccuracyasafunctionoftime-continues-valuedaccuracy,didfurtherimprovementofFFTBM.Namely,inthepastonlysinglevaluedaccuracyparametersforselectedtimewindowsandtimeintervalswerecalculated.TheobjectiveofthestudywastodemonstratethatthenewFFTBMisapowerfultoolforquantitativeassessmentofthermal–hydrauliccodes.Fordemonstration,thetestfromthefacilitysimulatingheavywaterreactorwasused.Theblindaccuracyanalysiswascompletedbasedonsolelyexperimentalandcalculateddata.However,shortdiscussionswereheldwiththerepresentativefromItaly(co-author,here)regardingphenomenologicalwindows,variablesandvoidfractionweightsselection.Ingeneral,theopenaccuracyanalysisconfirmedtheresultsobtainedinblindaccuracyanalysis.ThemainconclusionsfromaccuracyanalysisagreewiththeconclusionsfromtheSPEintercomparisonreport,whichwaswrittenindependently.Finally,theresultssuggestthattheaccuracyofthebestcalculationsoftheRD-14Mtestiscomparablewiththebestcalculationsoflightwaterreactorexperiments.