A theoretical study about U-235 enrichment by the chemical exchange method in U(IV)-U(VI) system on anion-exchange resins is presented. The U-235 isotope concentration profiles along the band were numerically calculated using an accurate mathematical model and simulations were carried out for the situation of product and waste withdrawal and feed supply. By means of numerical simulation, an estimation of the migration time, necessary for a desired enrichment degree, was obtained. The required migration distance, the production of uranium 3 at. % U-235 per year and the plant configuration are calculated for different operating conditions. An analysis of the process scale for various experimental conditions is also presented.