In order to recycle potentially valuable uranium and plutonium, the Purex process has been successfully used to reprocess spent nuclear fuel for several decades now at industrial scales. The process has developed over this period to treat higher burnup fuels, oxide as well as metal fuels within fewer solvent extraction cycles with reduced waste arisings. Within the context of advanced fuel cycle scenarios, there has been renewed international interest recently in separation technologies for recovering actinides from spent fuel. Aqueous fuel processing research and development has included further enhancement of the Purex process as well as the development of minor actinide partitioning technologies that use new extractants. The use of single cycle Purex solvent extraction flowsheets and centrifugal contactors are key objectives in the development of such advanced Purex processes in future closed fuel cycles. These advances lead to intensified processes, reducing the costs of plants and the volumes of wastes arising. By adopting other flowsheet changes, such as reduced fission product decontamination factors, U/Pu co-processing and Pu/Np co-stripping, further improvements can be made addressing issues such as proliferation resistance and minor actinide burning, without adverse effects on the products. One interesting development is the demonstration that simple hydroxamic acid complexants can very effectively separate U from Np and Pu in such advanced Purex flowsheets.

Simple hydroxamic acids are shown to be useful reagents for the separation of Np and Pu from U within simplified, single cycle Purex flowsheets. They are compatible with the use of centrifugal contactors and laboratory scale flowsheet trials with aceto-hydroxamic acid have demonstrated high actinide recoveries and decontamination factors on products for active feeds of up to 40 wt.% Pu. They therefore show many ideal characteristics for Pu and Np recovery within flowsheet options for actinide recovery in advanced fuel cycles. Furthermore, in order to optimize the routing of Np with the Pu product in advanced flowsheets, additional studies of Np extraction in the primary co-decontamination contactor, prior to U/Pu partition, have been undertaken, combining experiment, modelling and flowsheet tests.

An Advanced PUREX process has been developed for separation and recycling of neptunium from spent nuclear fuel. This work presents a new flowsheet simulation model for the extraction of neptunium using centrifugal contactors, where mass transfer is modeled using two-film theory and a linear driving force. Distribution coefficients and neptunium redox reactions are modeled using published models. Mass transfer between the organic and aqueous phases in the phase separation zone is shown to have a negligible effect. The model is applied to a previously tested flowsheet and its predictions are shown to be in good agreement with the experimental results.