Counter-currentflowlimitationsduringhotleginjectioninpressurizedwaterreactorsOriginalResearchArticle

Aone-dimensionalmodelispresentedtopredictcounter-currentflowlimitationsduringhotleginjectioninpressurizedwaterreactors.Differentfrompreviousmodels,itmayalsobeappliedincaseofhighFroudenumbersoftheliquidflow,suchastobeexpectedinthecaseofemergencycoolantinjectionthroughthehotleg.ThemodelhasbeenverifiedwithanextensiveexperimentalprogramperformedintheWENKAtestfacilityattheForschungszentrumKarlsruhe.Typicalflowregimeswereinvestigatedforawiderangeofflowconditions,simulatedwithairandwateratambientpressureandtemperature,inasimplifiedPressurizedWaterReactor(PWR)hotleggeometry.Dependingonthewaterandairflowrates,flowphenomenasuchasahydraulicjumpandflowreversalwereexperimentallyobserved.Thetheoreticalmodelshowsthatnotonlythenondimensionalsuperficialvelocitiesofliquidandgas,butalsotheFroudenumberoftheliquidattheinjectionpointandtheReynoldsnumberofthegasplayanimportantroleforthepredictionofflowreversal.IncaseofahighliquidinletFroudenumber,aflowreversalcouldonlybeobservediftheliquidflowbecamelocallysubcritical,i.e.ifahydraulicjumpoccurredinthechannel.Theflowreversalispredictedbythepresentedmodelwithgoodaccuracy.