報告書番号

T99004

タイトル（和文）

溶融塩からの超ウラン元素の還元抽出技術の開発 -連続式抽出法における抽出段数の評価-

タイトル（英文）

Development of Reductive Extraction Technology of Transuranic Elements from Molten Salt― Estimation of Stage Numbers at Continuous Extraction System ―

概要 （図表や脚注は「報告書全文」に掲載しております）

還元抽出工程に適した向流多段抽出の方法として連続式抽出法を考案した。本抽出法は相分離のための操作を必要としないため、簡便に実施できる抽出法と思われる。 また、本抽出法では所定の分離に要する抽出段数がバッチ式抽出法に比べて大幅に増加する可能性があるため、以下の手順で抽出段数を評価した。・溶融塩/液体Bi系にてNd、Gdを溶質とした抽出実験により抽出反応をモデル化し、本モデルで必要な速度定数を取得した。・溶融塩中のNdCl3を液体Bi中のGdで還元する工程を想定し、連続式抽出を行った場合の排出塩中のNdCl3濃度を上記のモデル及び速度定数を用いて計算し、バッ`式抽出での値と比較した。この結果、バッチ式抽出の処理速度に相当する流動率での抽出段数は、バッチ式抽出に比べて1～2段の増加に収まった。 よって、連続式抽出法での装置体積は大幅に増えることはなく、還元抽出工程への適用が期待できる。

概要 （英文）

In a reductive extraction step of pyrometallurgical recycle process, simplified counter-current multistage extraction system is required. For this purpose, continuous extraction system was invented and its stage numbers necessary for a separation was estimated. The continuous extraction system separates molten salt and liquid metal phase by the density difference of each phase and transfers them to the next extractor. Because no procedure for phase separation is necessary, this system is a simplified extraction method. In order to estimate stage numbers of this system, following experiments and calculations were conducted. From extraction experiments in molten salt/liquid bismuth systems using neodymium and gadolinium as solutes, extraction behavior was shown by a simplified model, which used bulk concentrations of solutes, and kinetic constants for this model were obtained. By using the extraction model and the kinetic constants, NdCl3 concentrations in the discharged salt from a continuous extraction system which extracts NdCl3 in the salt phase by Gd in the Bi phase were calculated. The concentrations showed that the stage numbers necessary for obtaining the separation comparing to batch extraction systems consist of three to five extraction stages were only one or two more than those of the batch extraction system. According to these results, it is expected that the continuous extraction system is suitable for the reductive extraction step.

報告者

キーワード