抄録
Caesium (Cs) is one of the known fission products (FPs) in spent fuel arising from nuclear electric power generation, which remains in the medium of pyroreprocessing after prolonged operation. We greatly hope to develop a new functional material that would make it possible to remove FPs, such as Cs, for regeneration of the medium. Iron phosphate glass could be used to immobilize high-level radioactive waste (HLW) and could function as a Cs sorpant. However, it must endure high temperatures from about 350°C, the melting point of LiCl-KCl electrolyte, to 600°C, the operational maximum temperature. In this study, we have successfully developed the iron phosphate glasses functioning as Cs sorpants and exhibiting heat resistance. To prevent glass softening at temperatures around 600°C, alkali metal oxides, alkaline-earth metal oxides, alumina, and titania were added into the Fe2O3-P2O5 glass. Through soak experiments of the glasses in molten salt (3LiCl-2KCl) containing CsCl, it was found that the glasses immobilized Cs by reacting with CsCl and formed the crystal phase of CsFeCl3 and/or Cs3FeCl6. This Cs sorption function is peculiar to the developed iron phosphate glasses.
