簡素化溶媒抽出法によるU, Pu及びNp共回収; フィード溶液及び洗浄液の高硝酸濃度化に伴うNpの抽出挙動への影響評価

U, Pu and Np co-recovery in the simplified solvent extraction process; The Extraction behavior of Np at the condition of high HNO concentration feed solution and scrubbing solution

中原 将海; 佐野 雄一   ; 宮地 茂彦 ; 小泉 務; 小山 智造; 青瀬 晋一

Nakahara, Masaumi; Sano, Yuichi; Miyachi, Shigehiko; Koizumi, Tsutomu; Koyama, Tomozo; Aose, Shinichi

先進湿式再処理プロセスに関連して、U, Pu及びNp共回収を目的とした簡素化溶媒抽出法の研究を進めている。フィード溶液及び洗浄液の酸濃度を上げることによりフィード溶液中及び遠心抽出器内においてNpの原子価を抽出性であるNp(VI)へ酸化させ、Npのラフィネートへのリーク防止を図った向流多段試験を行った。定常時におけるNpの物質収支では、ラフィネートへのリークをわずか1%に押さえることができた。また、MIXSET-Xにより抽出部のU, Pu及びNpの段効率は100%, 100%及び98.5%となり、逆抽出部のU, Pu及びNpの段効率は95%, 90%及び89%の値が得られた。

Concerning the advanced aqueous reprocessing system, the simplified solvent extraction process for U, Pu and Np co-recovery has been investigated. We carried out the counter-current experiment, which aimed for Np oxidation and extraction by high [HNO] condition. For preventing Np leakage to the raffinate, feed solution and scrubbing solution with high [HNO] were used, which would bring high [HNO] in the extraction section and efficient Np oxidation and extraction in this section. In addition, high [HNO] in the feed solution could help the pre-oxidation of Np to extractable Np(VI). In the steady state, the Np leakage to the raffinate could be kept under about 1%. The stage efficiencies for these elements were estimated by fitting the concentration profiles calculated by MIXSET-X into the experimental results. The stage efficiency of U, Pu and Np were evaluated 100%, 100% and 98.5% in the extraction section and 95%, 90% and 89% in the stripping section respectively.