Single-stage extraction test with continuous flow of molten LiCl-KCl salt and liquid Cd for pyro-reprocessing of metal FBR fuel

A single-stage extraction test with the continuous flow of both molten salt and liquid Cd was carried out as a preliminary step of the development of a multistage countercurrent extraction process for the pyrometallurgical reprocessing of metal FBR fuel. Ce, Gd, and Y were selected as the substitutes for U, other actinides, and rare-earth elements, respectively. More than 97% of Ce could be recovered in one of the experiments, in which 97% of Gd and 63% of Y were also recovered. This meant that high recovery yield could be obtained in the system, but mutual separation was not sufficient when the high recovery yield was required in a single-stage extraction. In another experiment in which the recovery yields of Ce, Gd, and Y were about 87, 70, and 8%, respectively, the separation factors of Gd and Y against Ce were 0.27 and 0.0092, respectively, which were about the same as their equilibrium values. The result showed that higher separation efficiency was achieved under the condition of relatively lower recovery yield. The mass transfer coefficient of rare-earth elements in the salt was estimated to be 0.14 cm/s, which was much larger than that in the previous experiments without a baffle plate in the extractor. (author)