In this paper, the application of small channels to the extraction separations in spent nuclear fuel reprocessing has been investigated via a modelling approach. The results are compared with conventional liquid-liquid extraction technologies such as mixer-settlers and pulsed columns, using models from the literature.In the model mass transfer, redox reactions, pressure drop and nuclear criticality are taken into account, as well as manifold and two-phase separator designs for the small-scale technology. The resulting model, posed as an optimisation problem, is a mixed integer nonlinear problem, implemented in the General Algebraic Modeling System (GAMS).An alternative flowsheet for the codecontamination section of the PUREX process, as a case study, has been investigated. The results show that the small-scale technology could be beneficial, in particular in terms of volumetric mass transfer coefficients, nuclear criticality safety and short residence time, which improves neptunium separation and reduces solvent degradation.