Extraction of key nuclides in carbonate environment using methyltrioctylammonium carbonate

Abstract To ensure the long-term development of nuclear energy, reduce the generation of nuclear waste, and achieve true greening of nuclear energy, a new type of spent fuel reprocessing technology called CARBEX has been proposed in recent years. However, research on the extraction stage within the CARBEX process is still relatively limited, usually focusing only on extraction separation studies with aqueous solutions containing only uranium, which cannot represent real reprocessing situations. This study used methyltrioctylammonium carbonate (MTOAC) as an extractant to separate and purify uranium from simulated spent fuel dissolution solutions. The behavior of MTOAC in extracting Cs, Te, Mo, Re, and U was systematically studied, and co-extraction separation experiments were conducted. This research is closer to the actual environment for spent fuel reprocessing and advances the industrialization process of the CARBEX method. The experimental results show that since the extraction mechanism of MTOAC is anion exchange, only Re and Mo can be extracted, while Cs and Te cannot. In addition, the high extraction efficiency of MTOAC for Re necessitates considering additional removal methods. Therefore, we propose a method of pre-treating spent nuclear fuel with a sodium hydroxide solution, which can remove almost all Re and most Mo, improving the feasibility of the CAEBEX process.