U, Pu and Np co-recovery in simplified solvent extraction process; Extraction behavior of Np using high HNO concentration at extraction section

Nakahara, Masaumi; Sano, Yuichi   ; Koizumi, Tsutomu

Concerning the advanced aqueous reprocessing system, we have been investigating a simplified solvent extraction process using TBP as an extractant for U, Pu and Np co-recovery. The experiment was conducted with low HNO concentration in the feed solution and high HNO concentration in the scrubbing solution, which was expected to bring a high HNO concentration into the extraction section and the efficient Np oxidation and extraction in this section. This experiment had been conducted with the dissolver solution of "JOYO" Mk-I and Mk-II irradiated MOX fuel. The Pu valence was adjusted to Pu(IV) by bubbling NOx gas into the feed solution. It was attempted to oxidize Np(V) to Np(VI) in the extraction section by adjusting HNO concentration of the feed and scrubbing solutions to 3.9M and 10M, respectively. After operation, the Np leakage to the raffinate could be kept under 6.3%. The decontamination factor of total- was 5.110 in this experiment.