StudyonjetbreakupbehavioratcoredisruptiveaccidentforfastbreederreactorOriginalResearchArticle

Itisimportanttoestimatethecoolingpossibilityofthemoltenjetincoolantduringacoredisruptiveaccident(CDA)ofafastbreederreactor(FBR).Inthepresentstudy,themoltenjetofU-alloy78simulatingthecorematerialisinjectedintothewatersimulatingthecoolant.Thevisualdataofthemoltenjetbreakupbehaviorisobservedbyusingthehigh-speedvideocamera.Thefrontvelocityofthemoltenjetisestimatedbyusingtheimageprocessingtechniquefromthevisualdata.Itshowsthatthefrontvelocityofthemoltenjetcanbedividedintothreetimeregions.Inthefirstregion,thefrontvelocityofthemoltenjetincreases.Inthesecondregion,thefrontvelocityofthemoltenjetsuddenlydecreases.Inthethirdregion,thefrontvelocityofthemoltenjetkeepsatlowandsteady.Infirstregion,thecolumndiameterofthemoltenjetdecreaseswiththepassageoftime.Atthelocationbetweenfirstregionandsecondregion,thecolumnofthemoltenjetbreaksupanddisappears.Inthepresentstudy,thejetbreakuplengthisdefinedasthedistancefromthewatersurfacetothelocationwherethejetcolumndisappears.Theresultsshowthatthejetbreakuplengthdependsontheinjectionnozzlediameter,butdoesnotdependonthejetpenetrationvelocity.ThistendencyagreeswiththepredictionbyEpsteinʹsequation.Aftertheexperiment,thesolidifiedfragmentsarecollectedandthemassmediandiameterismeasured.Themassmediandiameteriscomparedwiththeexistingtheories.Furthermore,amodeltoestimatethecoolingpossibilityduringaCDAofaFBRisconstructed,reflectingtheabove-mentionedresults.