Abstract: A process for reducing the concentration of fissionable uranium containing components of a feed material to below a target concentration level, the process having the steps of providing the feed material as an aqueous system of high-enriched uranyl nitrate hydrate (HE-UNH) wherein at least about 18% of the uranium therein is the .sup.235 U isotope, providing an aqueous dilution medium containing natural uranyl nitrate hydrate (NUNH) wherein at least about 90% of the uranium therein is the .sup.238 U isotope, forcing a diluent stream of the dilution medium through a jet pump to provide a suction region within the pump coextensive with the diluent stream, providing a feed fluid connection of the HE-UNH within the first vessel means with the suction region to cause a HE-UNH stream to flow into the suction region and intermix therein with the diluent stream to form a product stream of markedly reduced .sup.235 U concentration.