StabilityanalysisandnonlineardynamicsofnaturalcirculationboilingwaterreactorsOriginalResearchArticle

Numerousexperimentalandnumericalinvestigationshavebeenreportedinliteratureontheeffectofvariousparametersonthedynamicsofnaturalcirculationboilingwaterreactors(NCBWRs).DifferentfindingswerereportedinliteratureregardingtheeffectofvoidreactivitycoefficientandfueltimeconstantonType-IandType-IIinstabilities.ThepresentworkcontainsstabilityanalysisandnonlineardynamicsofNCBWRusingalumpedparametermodel.Thepurposeofthestabilityanalysisistoresolvedifferent,seeminglycontradictoryparametrictrendsreportedbypreviousauthors.Stabilityanalysisforthreedifferentsystemconfigurationshasbeendoneusingthesamemathematicalmodelandcomparedwiththefindingsreportedinliterature.Ithasbeenobservedthattheeffectsofvoidreactivitycoefficientandfueltimeconstantareinfluencedbygeometricalparametersandaredifferentfordifferentsystems.Nonlineardynamicsandbifurcationshavebeenstudiednumerically,foroneofthesystemconfigurations,forboilingchannelswithandwithoutriser.Thepossibilityofexistenceofstableandunstablelimitcycles,perioddoublings,andchaoticoscillationshasbeeninvestigated.TheeffectofvoidreactivitycoefficientonthenonlineardynamicshasbeenstudiedinbothType-IandType-IIregions.IntheType-Iregion,subcriticalHopfbifurcationleadingtounstablelimitcycle,aswellassupercriticalHopfbifurcationleadingtostablelimitcyclehavebeenfound.TheboilingchannelswithandwithoutriserhavebeenobservedtoundergochaoticoscillationsunderstrongreactivityfeedbackintheType-IIregion.Ithasbeenfoundthatthepresenceofriseraggravateschaoticoscillations.