PSB-VVERsimulationofKozloduyNPP“lossoffeedwatertransient”OriginalResearchArticle

ThispaperprovidesacomparisonbetweenthePSBtestfacilityexperimentalresultsobtainedduringthesimulationoflossoffeedwatertransient(LOFW)andthecalculationresultsreceivedbyINRNEcomputermodelofthesametestfacility.Integralthermal-hydraulicPSB-VVERtestfacilitylocatedatElectrogorskResearchandEngineeringCenteronNPPsSafety(EREC)wasputinoperationin1998.Thestructureofthetestfacilityallowsexperimentalstudiesundersteadystate,transientandaccidentconditions. RELAP5/MOD3.2computercodehasbeenusedtosimulatethelossoffeedwatertransientinaPSB-VVERmodel.ThismodelwasdevelopedattheInstituteforNuclearResearchandNuclearEnergyforsimulationoflossoffeedwatertransient. Theobjectiveoftheexperiment“lossoffeedwater”,whichhasbeenperformedatPSB-VVERtestfacilityissimulationofKozloduyNPPLOFWtransient.OneofthemainrequirementstotheexperimentscenariohasbeentoreproduceallmaineventsandphenomenathatoccurredinKozloduyNPPduringtheLOFWtransient.AnalyzingthePSB-VVERtestwithaRELAP5/MOD3.2computercodeasastandardproblemallowsinvestigatingthephenomenaincludedintheVVERcodevalidationmatrixas“integralsystemeffects”and”naturalcirculation“.ForassessmentoftheRELAP5capabilitytopredictthe“Integralsystemeffect”phenomenonthefollowingRELAP5quantitiesarecomparedwithexternaltrends:theprimarypressureandthehotandcoldlegtemperatures.InordertoassesstheRELAP5capabilitytopredictthe“Naturalcirculation”phenomenonthehotandcoldlegtemperaturesbehaviorhavebeeninvestigated. ThisreportwaspossiblethroughtheparticipationofleadingspecialistsfromKozloduyNPPandwiththesupportofArgonneNationalLaboratory(ANL),undertheInternationalNuclearSafetyProgram(INSP)oftheUnitedStatesDepartmentofEnergy