Hydride production in zircaloy-4 as a function of time and temperature

The experiments performed for this thesis were designed to define the primary\nprocess variables of time, temperature, and atmosphere for an engineering system that\nwill produce metal powder from recycled nuclear fuel cladding. The proposed system\nwill hydride and mill Zircaloy cladding tubes to produce fine hydride powder and then\ndehydride the powder to produce metal; this thesis is focused on the hydride formation\nreaction. These experiments were performed by hydriding nuclear grade Zircaloy-4\ntubes under flowing argon-5% hydrogen for various times and temperatures. The result\nof these experiments is a correlation which relates the rate of zirconium hydride\nformation to the process temperature. This correlation may now be used to design a\nmethod to efficiently produce zirconium hydride powder.\nIt was observed that it is much more effective to hydride the Zircaloy-4 tubes at\ntemperatures below the a-B-d eutectoid temperature of 540°C. These samples tended to\nreadily disassemble during the hydride formation reaction and were easily ground to\npowder. Hydrogen pickup was faster above this temperature but the samples were\ngenerally tougher and it was difficult to pulverize them into powder.