Abstract: A process irradiator includes a heavily shielded, generally cylindrical, housing with a heavily shielded top. A radiation source includes source elements in several tubes extending from the top into a shielded storage cask below the center of the housing floor. A circular track concentrically positioned relative to the track guides a motor-driven carousel carrying a number of turntables which carry material to be irradiated, the turntables being rotatable on their axes. A heavy shielded door provides access to the turntables which are successively rotated on the carousel to a position adjacent the door opening. A lifting structure on the top includes two or more lifting devices which permit selective lifting of the source elements from the storage cask into the housing. Interlock controls prevent the door from opening and the carousel from rotating unless all source elements are stored in the storage cask.