Speaker
Description
In a detritiation system, the function of recombiner is oxidation of tritium components. Detritiation system of a nuclear fusion facility should maintain its detritiation performance even in an event of accidents of the facility such as fire. The major technical background on recombiner design are detailed kinetics data, impact of gaseous impurities on kinetics, characteristics on pressure drop, impact of heat of reaction and effect of flow rate on kinetics. The volume of catalyst to be packed is evaluated by the overall reaction rate constant, required conversion efficiency and gas flow rate to be processed. The overall reaction rate constant has the effect of hydrogen concentration. Among the impurity gases that would be produced, water vapor, ammonia and halogenated acids affect tritium oxidation. It was demonstrated that the overall reaction rate constant is not affected by the scale of recombiner. Since the flow rate to be processed is large for the DS of a fusion facility, the amount of the catalyst to be packed inevitably increases. There is a strong need to set an allowable pressure drop so that the upstream line of the recombiner does not become pressurized. The height of the catalyst layer is determined from the allowable pressure drop. Then, the inner diameter of the recombiner is determined from the volume of catalyst and the layer height. In order to avoid tritium permeation from the recombiner surface, the adiabatic recombiner with a vacuum jacket can be applied. Consideration needs for the sudden rise of the catalyst temperature due to the reaction heat accompanying the combustion of the high concentration hydrocarbon gases. The maximum temperature of the recombiner relies on the necessity of oxidation of tritiated methane. The rate of tritiated methane produced by side reactions on the catalyst between methane and tritium is negligibly small.
