Irradiation targets for iridium and cobalt gamma sources

To produce gamma radiation sources for various purposes, technologies for making targets for iridium and cobalt irradiation were developed at INR Pitesti. Iridium and cobalt metals were sintered as disks of various size, coated with a nickel layer. The severe purity and density requirements make the stage of obtaining highly sinterable powders very critical. To obtain a sintered material of high quality, the sizes of the powder's particles must be small enough to ensure a high surface energy of the particles. Procedures to obtain the fineness required for the powders imply milling at high temperature, thermal treatments and chemical processing which are described. For iridium the procedure consists in milling with zinc at high temperature the iridium aggregates till the necessary fineness is reached (passing through the 30 μm sieve). The sintered stage is followed by nickel electrolytic coating to prevent contamination at irradiation and subsequent handling. Also mentioned are the technologies and installations developed for obtaining sintered cobalt for irradiation in adjuster rods at Cernavoda NPP, nickel coating of iridium and cobalt sources, cobalt oxalate precipitation, and sintering furnace installations as well as various devices for powder manipulation