Partitioning of minor actinides from HLLW using the DIAMEX process. Part 1 - Demonstration of extraction performances and hydraulic behaviour of the solvent in a continuous process

The French DIAMEX process shows very promising capabilities in separating minor actinides from HLLW. A counter-current centrifugal extractor experiment has been conducted to investigate the capabilities and possibilities of the DIAMEX process (hydraulic and extraction behaviour), for the separation of lanthanides from a simulated High Level Liquid Waste (HLLW), corresponding in concentration to a raffinate from the PUREX process. A hot batch test, using genuine HLLW; and a continuous counter-current experiment have verified the excellent extraction and hydraulic behaviour, respectively. With only four extraction stages in the cold experiment, lanthanide decontamination factors were higher than 2000, except for europium. Go-extraction of molybdenum and zirconium was efficiently prevented using oxalic acid in the feed solution. The back-extraction was very efficient, yielding in 4 stages more than 99% recovery of lanthanides. Palladium and ruthenium were more difficult to back-extract and for these elements further investigations are needed.