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Download fileThermally Stimulated Liquid Na–CaCO3 Reaction: A Physicogeometrical Kinetic Approach toward the Safety Assessment of Na-Cooled Fast Reactors
journal contribution
posted on 2022-02-15, 13:34 authored by Nobuyoshi Koga, Shin KikuchiIn this study, we characterized the
kinetic features of the thermally
stimulated reaction of CaCO3 with liquid Na as a model
process of the liquid Na–structural concrete reaction that
possibly occurs under a postulated severe accident in a Na-cooled
fast reactor. Two sampling conditions characterized by the dispersion
of CaCO3 powders in liquid Na and the limited contact of
liquid Na with the CaCO3 pellet surface were applied to
investigate the kinetics and physicogeometrical mechanism of the liquid
Na–CaCO3 reaction using differential scanning calorimetry
(DSC) and morphological observations of the products. Under both sampling
conditions, the exothermic liquid Na–CaCO3 reaction
started at the initial contact area of the reactants and proceeded
while liquid Na penetrated the CaCO3 powder and pellet,
exhibiting the apparent multistep reaction behaviors. Because of the
changes in the geometrical constraints of the liquid Na and CaCO3 contact induced by different thermal and mechanical events
in the reacting system, only the initial reaction step at the initial
contact area of the liquid Na and CaCO3 surface exhibited
acceptable repeatability to characterize the kinetic behavior. The
kinetic information of the first reaction step was extracted from
the exothermic DSC peak for the overall reaction using advanced kinetic
approaches to the multistep process, providing the kinetic parameters
supported by the defined physicogeometrical scheme of the reaction
to be used for simulating the liquid Na–CaCO3 reaction.
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postulated severe accidentcooled fast reactorscooled fast reactordefined physicogeometrical schemethermally stimulated reactioninitial reaction stepfirst reaction stepinitial contact areakinetic parameters supportedexothermic dsc peak3 </ subliquid na penetratedphysicogeometrical mechanismliquid nareaction startedlimited contactcontact inducedkinetic informationkinetic featureskinetic behaviorsampling conditionssafety assessmentreacting systempossibly occursmultistep processmorphological observationsmodel processmechanical eventsgeometrical constraintsdifferent thermal