Demonstration of uranium - plutonium separation and purification from spent nuclear fuel with monoamide solvent

International audienceIn the framework of the development of Generation IV reactors, innovative solvent extraction processes are under development for the reprocessing of spent nuclear fuels. Monoamides demonstrated their potentiality in the recovery and recycling of fissile materials, plutonium and uranium, as an alternative to TBP. First, they exhibit a good stability towards radiolysis and hydrolysis. Secondly, distribution ratios of Pu(IV) and U(VI) with monoamides are such that their extraction and separation is possible, without using any reducing agent for the uranium - plutonium partitioning. These potentialities were demonstrated during pilot tests performed on a genuine High Liquid Waste (HLW) in the CBP hot cell (Atalante facility). The HLW was obtained from the dissolution of irradiated uranium oxide fuels with burnup between 25 to 65 GWd/t. The contactor set-up consisted of six batteries of mixer-settlers. The first three mixer-settlers banks were devoted to the uranium and plutonium extraction and to the fission products scrubbing. The two following batteries were dedicated to the uranium – plutonium partitioning. The last step consisted in the stripping of uranium. In addition to the six mixer-settlers banks, the solvent clean-up was carried out thanks to three centrifugal contactors, allowing its recycling. After running at least 70 hours, more than 99.99% and 99.97% of respectively the initial uranium and plutonium were recovered with high decontamination factors versus fission products (mainly 99Tc, 106Ru and 137Cs). The organic and aqueous concentration profiles of uranium in the different stages of the process were analysed and these experimental data were compared with the calculated values. The comparison between experimental and predicted concentration profiles exhibits a good agreement between the two sets of data