Zirconium alloys hydriding by metal-plasma reaction

A new method for hydriding of Zirconium alloys, using metal-plasma reaction, was developed. The hydrogenous plasma was produced using a glow discharge between a stainless-steel electrode and zirconium alloy sample, at a given pressure P and temperature T of the gaseous hydrogen. An extremely fast hydriding reaction takes place. For a given hydrogen pressure and temperature, both the concentration and the kinetics of the process can be controlled by means of discharge current (e.g. the potential between electrodes). Conversely, for a given temperature and potential, the process is controlled by the hydrogen pressure. Different shapes of Zr-2.5%Nb, Zircaloy-4, Zr-45%U alloy specimens were used. The plasma development processes in the given working conditions, the mechanism of hydrogen uptake, the penetration of hydrogen bulk of samples and the microstructure obtained are briefly discussed. Comments on the advantages of the method and limits in his applicability are made. Some attempts to expending the metal-plasma reaction to oxidizing Zirconium alloys give promising results and are also discussed. (author)