Studyonthermal-hydraulicbehaviorduringmoltenmaterialandcoolantinteractionOriginalResearchArticle

Inacoredisruptiveaccident(CDA)ofaFastBreederReactor,thepostaccidentheatremoval(PAHR)iscrucialfortheaccidentmitigation.Themoltencorematerialshouldbesolidifiedinthesodiumcoolantinthereactorvessel.Thematerial,beingfragmentedwhilesolidificationandformingdebrisbed,willbecooledinthecoolant. Intheexperiment,moltenmaterialjetisinjectedintowatertoexperimentallyobtainthevisualizedinformationofthefragmentationandboilingphenomenaduringPAHRinCDA.Theexperimentshowsthatthebreakupofthemoltenmaterialintofinefragmentsisobservedatthefront,sideandmiddlepartofthejetduringveryshorttimeinterval.Thedistributedparticlebehaviorofthemoltenmaterialjetisobservedwithhigh-speedvideocamera.AndthevisualdataisanalyzedwithParticleImagingVelocimetry(PIV). Theexperimentalresultsarecomparedwiththeexistingtheories.Consequently,themarginalwavelengthonthesurfaceofawaterjetisclosetothevalueestimatedbasedontheRayleigh–Taylorinstability.Moreover,thefragmenteddropletdiameterobtainedfromtheinteractionofmoltenmaterialandwaterisclosetothevalueestimatedbasedontheKelvin–Helmholtzinstability.