B207 アークプラズマ加熱によるジルカロイ廃材の溶融 : 加熱条件と溶融状態および溶融時の核種挙動

Abstract

Among the various reprocessing wastes to be generated by future nuclear fuel cycles, the volume of hulls and end-pieces of cladded fuel structure segments must be reduced. Although are plasma melting has been considered a possible method, zircaloy, a major hull component, has an extremely high melting point, and experimental verification of are plasma melting has not been completed in Japan. In the study, we performed melting and solidification experiments in a small-sized are plasma melting furnace containing a graphite crucible, using unused zircaloy waste as simulated hull material. Its melting behavior was studied with respect to the following parameters : heating energy and heating atmosphere, and the method of introduction of the waste into the furnace. The study showed that for efficient melting, a small amount of waste at a time should be introduced into a nonwater-cooled crucible and that the waste should be briefly exposed to plasma. According to thermodynamic properties such as saturated vapor pressure of lanthanide elements and transuranic elements, surrogate elements are selected to simulate migration behavior of TRU elements during thermal plasma melting of TRU wastes. These elements are simultaneously melted by thermal plasma heating with zircaloy. The surrogate elements have a tendency not to migrate into dust.