Separation of actinoids from HLW by thiacalix[4]arene compound impregnated silica ion-exchanger

If trivalent actinoids such as Am can be separated from high-level radioactive liquid waste (HLLW) generated by the PUREX process, long-term heat and radiation hazards can be significantly reduced in the disposal of this waste. This paper reports the effective separation of Am through the use of a chelating ion-exchange method that uses an octylphenyl-N,N-diisobutylcarbomoyl phosphine oxide (CMPO) or thiacalix[4]arene compound impregnated silica ion-exchanger. The separation of Cs and Sr from HLLW can be achieved using a CMPO impregnated silica ion-exchanger (CMPO-exchanger). Actinoids and lanthanoids can then be eluted from the CMPO-exchanger, with the resulting solution then treated to separate the actinoids using a thiacalix[4]arene compound impregnated silica ion-exchanger. Thiacalix[4]arene compound impregnated silica ion-exchangers have been shown to effectively separate actinoids from lanthanoids in a weak-acid solution. The influence of gamma ray irradiation on adsorption is also investigated. The adsorption of Am remains high even after irradiation of the ion-exchanger.