Innovative SANEX process for trivalent actinides separation from PUREX raffinate

Abstract

Recycling of nuclear spent fuel and reduction of its radiotoxicity by separation of long-livedradionuclides would definitely help to close the nuclear fuel cycle ensuring sustainability ofthe nuclear energy. Partitioning of the main radiotoxicity contributors followed by theirconversion into short-lived radioisotopes is known as partitioning and transmutation strategy.To ensure efficient transmutation of the separated elements (minor actinides) the content oflanthanides in the irradiation targets has to be minimised. This objective can be attained bysolvent extraction using highly selective ligands that are able to separate these two groups ofelements from each other.The objective of this study was to develop a novel process allowing co-separation of minoractinides and lanthanides from a high active acidic feed solution with subsequent actiniderecovery using just one cycle, so-called innovative SANEX process. The conditions of eachstep of the process were optimised to ensure high actinide separation efficiency. Additionally,screening tests of several novel lipophilic and hydrophilic ligands provided by University ofTwente were performed. These tests were aiming in better understanding the influence of theextractant structural modifications onto An(III)/Ln(III) selectivity and complexationproperties.Optimal conditions for minor actinides separation were found and a flow-sheet of a newinnovative SANEX process was proposed. Tests using a single centrifugal contactorconfirmed high Eu(III)/Am(III) separation factor of 15 while the lowest SFLn/Am obtained was6,5 (for neodymium). In addition, a new masking agent for zirconium was found as asubstitution for oxalic acid. This new masking agent (CDTA) was also able to maskpalladium without any negative influence on An(III)/Ln(III). Additional tests showed noinfluence of CDTA on plutonium present in the feed solution unlike oxalic acid which causesPu precipitation. Therefore, CDTA was proposed as a Zr masking agent in GANEX processwhere high content of Pu is expected. In this so called GANEX (Group Actinide Extraction)process all actinides are separated as a group from the lanthanides and fission products.Within the new ligands delivered by University of Twente four water-soluble and fourlipophilic ones showed good An(III)/Ln(III) complexation thus they deserve further studieswith possible implementation in already existing or new processes