Separation of actinides from rare earth elements by means of molten salt electrorefining with anodic dissolution of U-Pu-Zr alloy fuel

Electrorefining is the main process for pyro-reprocessing of the fuel of a metallic fuel FBR. To obtain a basic knowledge of electrorefining technology, a series of experiments was carried out with unirradiated fuel alloy. The alloy, 71U-19Pu-10Zr (wt.%), was dissolved anodically into a molten LiCl-KCl bath at 753 K. Simultaneously, Pu and U were recovered into the Cd cathode with small amounts of minor actinides, Zr and rare earth elements (REs). The separation factors of U, Np, Am, Cm and Ce against Pu, derived from the composition of recovered deposits and of the salt bath, were about 2.04, 0.949, 0.597, 0.534 and 0.0393, respectively, which are similar to the equilibrium values observed in a distribution experiment in a LiCl-KCl/Cd system. This demonstrates that electrorefining achieves the separation of actinides from REs. The anodic dissolution of the alloy was found to progress from the outside, leaving a dense layer containing salt and Zr metal around the alloy surface. It was found that more than 99.9% of both U and Pu could be dissolved from the alloy and about 55% of Zr remained in this layer.