Study of the diffusion of oxygen in alpha--zirconium by means of nuclear microanalysis

Polycrystalline zirconium samples were oxidized in pure oxygen under atmospheric pressure at temperatures ranging from 700° to 845°C and for times up to 400 hr. The diffusion of oxygen in the metal, beneath the oxide layer formed, was studied using a direct quantitative method of analysis based on the observation of the nuclear reaction. It was found that at a given temperature the oxygen concentration profiles, referred to the oxidemetal interface, may be superimposed after scaling by a factor. The results may be fitted assuming a concentration independent diffusion coefficient, the oxygen concentration at the oxide‐metal interface being constant and nearly equal to the saturation value, around 30 atom per cent. An activation energy was found for the process. Identical results were obtained in air, showing that, at atmospheric pressure, nitrogen in the air plays a negligible role in the dry corrosion of zirconium.