Effect of oxide ions on separation factors of actinides from lanthanides in reductive extraction

還元抽出によるランタノイドとアクチノイドの分離係数への酸化物イオンの影響

森山 裕丈*; 森谷 公一*; 戸田 太郎*; 林 博和 

Moriyama, Hirotake*; Moritani, Kimikazu*; Toda, Taro*; Hayashi, Hirokazu

溶融塩と液体金属を用いた還元抽出系であるNaCl-KCl/液体Ga系(1073K)において、Am, Ce及びEuの分配係数を測定した。溶質濃度を変化させた実験結果より、分配係数は系内の酸化物イオン濃度に強く影響され、AmOやCeOなどが生成することが示唆された。また、Amのマスバランスは酸化塩化物や酸化物といった沈殿物の生成に影響されることが示された。これらを考慮に入れると、この系におけるAmとCeの分離係数は下限値として約30と評価された。

The distribution coefficients of Am, Ce, and Eu between the salt and metal phases were measured at 1073 K in a reductive extraction system of equimolar NaCl-KCl melt and liquid Ga, which were expected to be higher from a thermodynamic point of view. By changing some solute concentrations, it was observed that the distribution coefficients were much dependent on the oxide ion concentration in the system, possibly due to the formation of such compounds as AmO and CeO. Also, in some runs, the mass balance of Am was affected possibly by the formation and precipitation of its oxychloride and/or oxide. By taking the observations into consideration, the separation factor between Am and Ce was obtained to be about 30 as a lower limit in the present system.