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

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

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.