Development of pyrometallurgical partitioning technology of long-lived nuclides. Demonstrational experiments on separation and recovery of actinide elements from mixed molten salt

Demonstrational experiments on the separation and recovery of actinide elements from mixed molten salt containing noble metal, alkaline earth, and rare-earth elements (REs) were conducted at both 1/6000 and 1/2000 of industrial scale. The experiments involved two reductive extractions, electrorefining, multistage extractions using bismuth as a solvent, and electrorecovery of transuranic elements (TRUs). The electrorefining process yielded cathode deposits with actinide purities greater than 99wt.% of the deposited metal. The multistage extraction processes also yielded products with TRU/RE weight ratios of 2.45 and 3.21, compared to the target of 1.0. Overall carryovers of TRUs to the waste product in the 1/6000-scale experiment were less than 0.62% of finally detected TRUs, compared to the target of 1.0%. Though the final mass balances of TRUs ranged between 65% and 74% in this experiment, the missing amounts were assumed to have remained in the system and to be recoverable. Accordingly, recovery of more than 99% of TRUs was demonstrated. Though overall carryovers of TRUs to the waste product in the 1/2000-scale experiment ranged between 1.5% and 3.2%, this was due to sample analysis failure, and the values would have been less than 1.0% had sample analysis been available to guide the operation of the multistage extraction process. The cumulative results of these experiments demonstrate that CRIEPI's pyropartitioning process will meet the process goals for actinide separation and product purity. (author)