核種分離抽出剤の調査

Literature survey on extractants for liquid-liquid extraction applied to nuclear fuel cycles

小沢 正基; 富樫 昭夫

not registered; not registered

ウラン製錬及び使用済み燃料の再処理で, これまでに実用化されたプロセスに使用される抽出剤について,3価のアクチニドの抽出挙動について調査した。さらに3価のアメリシウムを抽出する抽出剤について,3価のアクチニドの抽出特性,抽出機構,抽出剤の構造,抽出された錯体の構造等について調査を行った。これらの調査結果をもとに,Purexプロセスでは抽出されない3価のアメリシウムを除去・回収し,燃料としてリサイクルするために有効な抽出剤について検討した。硝酸濃度の高い(13M)溶液から,3価のアクチニドを効果的に抽出できる抽出剤として,2座配位中性有機化合物(ジフォスフィンジオキサイド,カルバモイルメチルフォスフィンオキサイド,プロパンジアミド等)を挙げることができる。新しい抽出剤あるいは抽出剤システムの研究は,1)これまでの抽出剤と異なった抽出機構を持った抽出剤の研究および2)これまでの抽出剤を含む効果的な相乗付加剤-希釈剤システムの研究を指定することになると思われる。

In the field of uranium ore refining and spent fuel reprocessing, a lot of extractants capable of recovering actinides have been innovated, and some of which have been developed in actual industrial scale processes. Extractability against trivalent actinides on each extractants were evaluated in this report. And as for the compounds which showed excellent extractability for Americium, their extraction characteristics for trivalent actinides, such as extraction behavior, mechanism, ligand structure and conformation of complexes, were evaluated, and filed as data-base. Based on these works, some of extractant were newly identified as candidate to apply Americium recovering. The most appropriate compounds for trivalent actinide separation can be generally found in the neutral bidentate organic compound groups: Especially, some derivatives belongs to Diphosphineoxide, Carbamoyl-methylphosphine oxide and Propandiamide were superior to give sufficiently excellent property even in higher nitric acid(13M) solutions. Innovative research towards developping new extractants and extraction system seems to be directed to ; (1)investigate new types of extractant sustained by a different kind of complexing mechanism, (2)evaluate synergistic effect of adducts, diluents even including conventional extractants.