Direct separation of uranium from lanthanides (La, Nd, Ce, Sm) in oxide mixture in LiCl-KCl eutectic melt

Abstract

This paper reports the direct separation of U from lanthanides (Ln) in oxide mixtures in LiCl-KCl eutectic, a method that could simplify the pyrometallurgical reprocessing of UO2-based spent fuels. In the melt, the mixture of UO2 and lanthanide oxides (Ln2O3/LnO2) was chloridized by AlCl3, and then U was selectively recovered by forming U-Al alloys through the redox reactions of U(IV)/U(III) and U(III)/AlxU. The results showed that U could be efficiently separated from lanthanides with high separation factors (SFU/La = 1.1 × 104, SFU/Ce = 1.6 × 105, and SFU/Sm = 2.5 × 104). X-ray diffraction analysis indicated the predominant separation products to be Al3U and Al4U, whereas the real extraction rate of U was probably affected by trace amounts of O2− in the melt. For the first time, single-cell operation to separate U from Ln in mixed oxides is shown to be feasible by using AlCl3 as chlorination agent followed by electrodeposition.