VibrationanalysisofadummyfuelrodcontinuouslysupportedbyspacergridsOriginalResearchArticle

Thefuelrodsinthepressurizedwaterreactorarecontinuouslysupportedbyaspringsystemcalledaspacergrid(SG),whichisoneofthemainstructuralcomponentsforthefuelrodcluster(fuelassembly).Thefuelrodshaveavibrationbehaviorwithinthereactorduetocoolantflow.Sincethevibration,whichiscalledflow-inducedvibration,canwearawaythesurfaceofthefuelrod,itisimportanttounderstanditsvibrationcharacteristics.Inthispaper,amodaltestingandafiniteelement(FE)analysisusingABAQUSonadummyfuelrodcontinuouslysupportedbyOptimizedHType(OHT)andNewDoublet(ND)spacergridsareperformedtoobtainthevibrationcharacteristicssuchasnaturalfrequenciesandmodeshapesandtoverifytheFEmodelused.TheresultsfromthetestandtheFEanalysisarecomparedaccordingtomodalassurancecriteriavalues.ThenaturalfrequencydifferencesbetweenthetwomethodsaswellasthemodecomparisonresultsfortherodwiththeOHTSGarebetterthanthosewiththeNDSG.Thatis,inthecaseoftheNDgridmodelusingbeam-springelements,therewasalargediscrepancybetweenthetwomethods.Thus,wetriedtomodifytheFEmodelfortheNDSGconsideringthecontactphenomenabetweenthefuelrodandtheSG.Theresultsofthenewmodelshowedagoodagreementwiththeexperimentcomparedwiththoseofabeam-springmodel.