Dynamicanalysisofmultiplenuclear-coupledboilingchannelsbasedonamulti-pointreactormodelOriginalResearchArticle

Thisworkinvestigatesthenon-lineardynamicsandstabilitiesofamultiplenuclear-coupledboilingchannelsystembasedonamulti-pointreactormodelusingtheGalerkinnodalapproximationmethod.ThenodalapproximationmethodforthemultipleboilingchannelsdevelopedbyLeeandPan[Lee,J.D.,Pan,C.,1999.Dynamicsofmultipleparallelboilingchannelsystemswithforcedflows.Nucl.Eng.Des.192,31–44]isextendedtoaddressthetwo-phaseflowdynamicsinthepresentstudy.Themulti-pointreactormodel,modifiedfromUehiroetal.[Uehiro,M.,Rao,Y.F.,Fukuda,K.,1996.Linearstabilityanalysisoninstabilitiesofin-phaseandout-of-phasemodesinboilingwaterreactors.J.Nucl.Sci.Technol.33,628–635],isemployedtostudyamultiple-channelsystemwithunequalsteady-stateneutrondensitydistribution.Stabilitymaps,non-lineardynamicsandeffectsofmajorparametersonthemultiplenuclear-coupledboilingchannelsystemsubjecttoaconstanttotalflowrateareexamined.Thisstudyfindsthatthevoid-reactivityfeedbackandneutroninteractionsamongsubcoresarecoupledandtheircompetingeffectsmayinfluencethesystemstabilityunderdifferentoperatingconditions.Forthosecaseswithstrongneutroninteractionconditions,bystrengtheningthevoid-reactivityfeedback,thenuclear-coupledeffectonthenon-lineardynamicsmayinducetwounstableoscillationmodes,thesupercriticalHopfbifurcationandthesubcriticalHopfbifurcation.Moreover,forthosecaseswithweakneutroninteractions,byquadruplingthevoid-reactivityfeedbackcoefficient,period-doublingandcomplexchaoticoscillationsmayappearinathree-channelsystemundersomespecificoperatingconditions.AuniquetypeofcomplexchaoticattractormayevolvefromtheRosslerattractorbecauseofthecoupledchannel-to-channelthermal-hydraulicandsubcore-to-subcoreneutroninteractions.Suchacomplexchaoticattractorhastheimbeddingdimensionof5andthefractaldimensionrangingfrom1.26to1.35.