Oxidation Investigation of NBG-18 Nuclear-Grade Graphite

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Conference Proceeding

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The oxidation kinetics of NBG-18 nuclear graphite was investigated between 500 and 775°C with oxygen partial pressures ranging from 10 to 40 kPa. Using a phenomenological shrinking-core model, reaction rates normalized to the reactive surface area were determined. In addition, a more rigorous, mechanism-based model is proposed for the reaction rate of nuclear graphites based on observed spill-over of the carbon-oxygen surface intermediate onto the graphite basal plane. This mechanistic model suggests the reaction is controlled simultaneously by the dissociative chemisorption of oxygen and the desorption of reactive surface intermediates to form CO(g) and CO2(g). The activation energies for these processes were approximated as180±10, 260±10 and 190±10 kJ/mol, respectively.

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