Application of supercritical fluid extraction to metal separation in the field of nuclear technology

Meguro, Yoshihiro  ; Tomioka, Osamu ; Takahashi, Kuniaki ; Wada, Ryutaro*; Yamamoto, Seiichi*; Fukuzato, Ryuichi*

A large-scale apparatus having a reaction vessel of ca. 4000 cm was developed for supercritical CO leaching. An ultrasonic wave oscillator, stirring device, and piston compressor were equipped to the apparatus to enhance mass transfer rate of substances in supercritical CO. A sea sand sample, an incinerated ash sample, and a porous alumina brick sample, in which uranium oxide was adsorbed, were prepared as simulated samples of radioactive wastes and uranium was tried to remove from these samples to supercritical CO including nitric acid - tri-n-butyl phosphate complex as a reactant using the apparatus. By several times of the uranium separation, more than 99% of uranium was removed from the sea sand sample and the ash sample. When the mass transfer enhanced system was operated, it was confirmed that separation efficiency of uranium was improved and then 99% of uranium could be removed form the ash sample.