Extractant separation in DIAMEX-SANEX process

International audienceIn the frame of the French radioactive waste management Acts of December 1991 and June 2006, minor actinide separation processes have been developed to significantly decrease the radiotoxicity of the ultimate waste produced by the nuclear industry. For actinide/lanthanide separation, several routes are possible, either with two cycles using two different solvents (generally DIAMEX for the first one, and SANEX for the second one), or with a single cycle and the same solvent during the whole process. The DIAMEX-SANEX concept described in this paper is a sort of intermediate between these two strategies: the organic phase consists of a cationic exchanger and the N,N'-dimethyl-N,N'dioctylhexylethoxymalonamide, (DMDOHEMA), which play different role in distinct key stages of the process. The main idea of this process is to split the organic phase in two solvents: one containing the DMDOHEMA, the other the acidic extractant. So this latter doesn't interact with DMDOHEMA during the first extraction step. This paper describes some results obtained with di-nhexyl phosphoric acid (HDHP), which fulfils the required criteria for the process. For instance, this reagent can easily extract lanthanides from a weak acidic aqueous solution, and it can be stripped selectively from DMDOHEMA, thanks to a basic solution