MechanismanalysisonflowexcursionofanaturalcirculationwithlowsteamqualityOriginalResearchArticle

FlowexcursionwasobservedonthenaturalcirculationtestloopHRTL-5,whichsimulatesthegeometryandsystemdesignofthe5MWnuclearheatingreactor.Bymeansofself-developedcomputationalcodes,asetoftoolsusedforanalyzingtheflowcharacteristicsofthenaturalcirculationhavebeenpresented,includingthecharacteristiccurves,operationalcurveandthebifurcationcurve.Thetwo-dimensionaldisturbanceanalysisisadoptedtoexplainthemechanismoftheflowexcursion.Analyticalresultshows:(1)flowexcursioncanoccurinanaturalcirculationsystematasuitablegeometryandthermal–hydraulicconditions.(2)Characteristiccurves,operationalcurve,bifurcationcurve,andthetwo-dimensionaldisturbanceanalysisaretheavailablemethodtoanalyzetheflowexcursionofthenaturalcirculation.(3)Theflowexcursionispriortothelowsteamqualitydensitywaveoscillation.(4)Theonsetoftheflowexcursionisthetangencypointofthedriveforcecurveandtheflowresistancecurve.(5)Tooperateatlowheatfluxtoincreasetheinlettemperatureistheeffectualapproachtotransferfromthepressurizedwaterstatetotheboilingwaterstate,inwhichtheflowexcursionandthelowsteamqualitydensitywaveoscillationcanbeavoided.