Abstract: In a process for decontaminating a nuclear process off-gas stream, oxygen and oxides of nitrogen are removed by catalytic reaction with hydrogen. The feed gas stream is then passed serially through a drier, a carbon dioxide adsorber and a xenon adsorber to sequentially remove water, CO.sub.2 and xenon therefrom. The feed gas exiting the xenon adsorber is passed to a krypton recovery process wherein krypton is concentrated to a first level in a primary distillation column, partially evaporated to increase concentration thereof and is brought to a concentration of approximately 90 mol % or greater in a second distillation column thereby enabling efficient storage of a radioactive krypton product. The xenon gas removed from the main feed stream in the xenon adsorber is passed to a freezeout heat exchange device to concentrate xenon to approximately 99% or greater, balance krypton.