Author/Authors :
H.Alsmeyer، نويسنده , , G.Albrecht، نويسنده , , L.Meyer، نويسنده , , W.H?fner، نويسنده , , C.Journeau، نويسنده , , M.Fischer، نويسنده , , S.Hellman، نويسنده , , M.Eddi، نويسنده , , H.-J.Allelein، نويسنده , , M.Bürger، نويسنده , , B.R.Sehgal، نويسنده , , M.K.Koch، نويسنده , , Z.Alkan، نويسنده , , J.B.Petrov، نويسنده , , M.Gaune-Escard، نويسنده , , E.Altstadt، نويسنده , , G.Bandini، نويسنده ,
Abstract :
Theprojectonex-vesselcoremeltstabilizationresearch(ECOSTAR)startedinJanuary2000tobeconcludedbyendof2003.Theprojectisperformedby14partnerinstitutionsfromfiveEuropeancountriesandinvolvesalargenumberofexperimentswithlow-andhigh-temperaturesimulantmeltsandrealcoriumatdifferentscales.ModeldevelopmentandscalinganalysisallowsapplicationoftheresearchresultstoexistingandtofutureLWRsintheareaofreactordesignandaccidentmitigation.Theprojectisorientedtowardtheanalysisandmitigationofsevereaccidentsequencesthatcouldoccurintheex-vesselphaseofapostulatedcoremeltaccident.Theissuesare:(1)thereleaseofmeltformthepressurevessel,(2)thetransferandspreadingofthemeltonthebasement,(3)theanalysisofthephysical–chemicalprocessesthatareimportantforcoriumbehaviorespeciallyduringconcreteerosionwithonsetofsolidification,and(4)stabilizationofthemeltbycoolingthroughdirectwatercontact.Theresultsachievedsofarresolveanumberofimportantissues:theamountofmeltthatcouldbetransferredatRPVfailurefromtheRPVintothecontainmentcanbesubstantiallyreducedbyloweringtheresidualpressureintheprimarycircuit.ItisfoundthatmeltdispersionalsostronglydependsonthelocationoftheRPVfailure,andthatlateralfailureresultsinsubstantiallylessmeltdispersion.Duringmeltrelease,theimpingingmeltjetcoulderodepartsoftheupperbasementsurface.Jetexperimentsandaderivedheattransferrelationallowestimationofitscontributiontoconcreteerosion.Spreadingofthecoriummeltontheavailablebasementsurfaceisanimportantprocess,whichdefinestheinitialconditionsforconcreteattackorfortheefficiencyofcoolingincaseofwatercontact,respectively.Validationofthespreadingcodesbasedonalarge-scalebenchmarkexperimentisunderwayandwillallowdeterminationoftheinitialconditions,forwhichacoriummeltcanbeassumedtospreadhomogeneouslyovertheavailablesurface.ExperimentswithUO2-basedcoriummeltshighlighttheroleofphasesegregationduringonsetofmeltsolidificationandduringconcreteerosion.Tocoolthespreadcoriummelt,theefficacyoftopfloodingandbottomfloodingisinvestigatedinsmall-scaleandinlarge-scaleexperiments,supportedbymodeldevelopments.Projectassessmentiscontinuingtoapplytheresultstopresentandfuturereactors.
