Distribution of plutonium, americium and interfering fission products between nitric acid and a mixed organic phase of TODGA and DMDOHEMA in kerosene, and implications for the design of the “EURO-GANEX” process

For the homogeneous recycling of actinides from spent nuclear fuels, within the future nuclear fuel cycle based on a transition to fast neutron reactors, a new GANEX (Grouped Actinide Extraction) process is under development. This potentially provides a simpler, more proliferation resistant hydrometallurgical process for recycling actinides. The so-called EURO-GANEX process is based on liquid-liquid extraction into an organic phase comprising 0.2 mol/L TODGA and 0.5 mol/L DMODHEMA in an odourless kerosene diluent. Before testing the EURO-GANEX process with dissolved fast reactor spent fuel, data are required on the distribution ratios of likely problematic fission products (Fe, Sr, Zr, Mo, Tc, Ru, Pd) under typical extraction and scrubbing conditions. Also, suitable conditions must be defined for the selective backwashing of the transuranic actinides (specifically plutonium and americium) in the presence of extracted lanthanide elements. Distribution ratio data obtained indicate that conditions can be defined that prevent iron and strontium break through whilst maintaining actinide extraction across the extract-scrub contactors although some accumulation may occur. Zirconium and palladium extraction can be effectively inhibited by a polycarboxylate ligand: CDTA. However, technetium and molybdenum are likely to be extractable in the first contactor due to high distribution ratios and no significant suppression with CDTA. Ruthenium may be partially extracted but behaviour is complex in nitric acid. It was also shown that plutonium and americium can be efficiently separated from lanthanides by stripping with a combination of a sulphonated bis-triazinyl pyridine (BTP) ligand and acetohydroxamic acid (AHA) for plutonium concentrations ranging from < 1 mg/L to 10 g/L plutonium solvent loading