Malonamides for the multi-recycling of nuclear spent fuel
Résumé
Nuclear energy is the principal source of electricity in France; the actual nuclear fuel consists of either uranium oxide or a mixture of uranium and plutonium oxide. After its use in the nuclear reactor, spent nuclear fuel still contains a significant amount of uranium and plutonium, which can be recovered and reused as nuclear fuel. The actual recycling process PUREX (Plutonium Uranium Refining by Extraction) involves a liquid-liquid extraction process using TriButylPhosphate (TBP) as extracting molecule. Although this solvent has been used for decades, it presents some limitations such as its non-incinerable nature, the formation of troublesome degradation products moreover; the uranium/plutonium separation is performed by using a reducing agent. As an alternative, malonamides molecules can be used to extract uranium (VI) and plutonium (IV) from spent nuclear fuel [1]
Malonamides show to be good extractants of uranium (VI) and plutonium (IV). These molecules are only composed of C, H, O and N atoms hence they are entirely incinerable solvents, and their degradation products are less disturbing to the recycling process.[1] However, malonamides also co-extract minor actinides and Lanthanides.[2] This work aims to study the possibility of adapting malonamides family to extract selectively U (VI) and Pu (IV), without extracting minor actinides and lanthanides also develop a simple formulation that separates uranium (VI) and plutonium (IV) without modifying their oxidation state. Deep characterization using spectroscopy techniques (IR, NMR ...), SAXS, ESI-MS and ICP-MS will then performed to understand extraction and selectivity properties establish the speciation, have a description of the cation's coordination sphere and solution organization
Thus, several malonamides systems (Ligands/diluents) have been investigated on U (VI) and Th (IV). The effects of structural modifications on extraction performances and separation possibility have been evaluated. Third phase formation (splitting of the organic phase into two different phases) and aggregation influence on extraction process has conjointly been taken into account.