Re-evaluation of radiation-energy transfer to an extraction solvent in a minor-actinide-separation process based on consideration of radiation permeability

Toigawa, Tomohiro   ; Tsubata, Yasuhiro   ; Kai, Takeshi   ; Furuta, Takuya   ; Kumagai, Yuta   ; Matsumura, Tatsuro  

Absorbed-dose estimation is essential for evaluation of the radiation feasibility of minor-actinide-separation processes. We propose a dose-evaluation method based on radiation permeability, with comparisons of heterogeneous structures seen in the solvent-extraction process, such as emulsions forming in the mixture of the organic and aqueous phases. A demonstration of radiation-energy-transfer simulation is performed with a focus on the minor-actinide-recovery process from high-level liquid waste with the aid of the Monte Carlo radiation-transport code PHITS. The simulation results indicate that the dose absorbed by the extraction solvent from alpha ray depends upon the emulsion structure, and that from beta and gamma ray depends upon the mixer-settler-apparatus size. Non-negligible contributions of well-permeable gamma rays were indicated in terms of the plant operation of the minor-actinide-separation process.