⁶⁰Co Heat-source Encapsulation

The properties of nickel- and cobalt-based heat-resistant alloys were studied to determine their suitability as capsules for irradiated cobalt in heat sources. Capsules with 0.1-in.-thick walls can be used with confidence at normal operating conditions of at least 800°C for one year in air. Operation either for longer times or at higher temperatures (up to 1000°C) may be feasible; the limiting properties will probably be grain-boundary diffusion by cobalt and creep strength. The most promising alloys currently under study for encapsulating cobalt are: Inconel 600^®, TD Nickel Chromium, TD Nickel, and Haynes 25^®. The performance of these materials is being demonstrated in a continuing program of heating tests of experimental radioactive capsules at 850 to 1000°C for extended times.