Pyrochemical separation of transuranium elements

In order to utilize atomic energy continuously in future, the solution of the various subjects related to nuclear fuel cycle has been demanded. One of the subjects is the completion of nuclear fuel cycle, and the disposal of high level radioactive waste and its safety are being developed. Another important subject is the improvement of the safety and economical efficiency of nuclear fuel cycle. Transuranium elements are related to all these subjects of nuclear fuel cycle, and various investigations have been carried out including the strategy of group partition and annihilation. In this paper, as an example of the research on the group partition of transuranium elements, the research on pyrochemical process that the authors have been advanced is introduced. As the method of the group partition of radioactive waste, the wet process following the PUREX process has been studied so far. The dry process utilizes melted salts or liquid metals. The comparison of the wet and dry processes is discussed. Pyrochemical process is a dry separation process. The experiment on the dependence of the separation coefficients of actinide and lanthanide elements on the kinds of liquid metals is reported. The characteristics superior to those of the wet process can be expected for the pyrochemical process. (K.I.)