[en] A method for producing ⁹⁹Mo from neutron-irradiated UO₂ by sublimation has been developed. The UO₂ was converted to the pulverized U₃O₈ through heating at 600⁰C under oxygen atmosphere. Molybdenum-99 was sublimated as MoO₃ at 1300⁰C under vacuum and deposited on a collector. Fundamental studies have been made on the irradiation technique of the UO₂, on the temperature dependence of sublimation of ⁹⁹Mo, and also on the trapping of ¹³¹I. As a next step, a production apparatus was constructed on a practical scale, and ⁹⁹Mo successfully recovered as a final product with a total yield of above 70%. Finally, the remote-controlled mechanism for handling the apparatus was conceptually designed. In addition, ¹³²I was milked in a high yield from ¹³²Te of a by-product. (author)