Abstract: A mathematical model for the quasi-ideal cascade with an additional feed flow and losses of working substances was established. Analytical relations to calculate the relative product and waste flows, component concentrations in the product and waste flows and the total substance flow in this cascade model were obtained by solving cascade equations. Cascade calculations were performed for separation of the recycled uranium. It was analyzed that the effects of loss factor and ratio between base and additional flows on the product concentration of cascade, in which the natural uranium was fed as a base feed flow and the recycled uranium as an additional one.