In-situ investigation of hydrogen diffusion in Zircaloy-4 by means of neutron radiography

Abstract

The hydrogen diffusion from the gas phase into Zircaloy-4 solid cylinders was investigated at various temperatures between 823 and 1473 K. Diffusion coefficients were fitted using axial hydrogen distributions for all temperatures investigated. The activation energy of the hydrogen diffusion was calculated for temperatures at which the bcc β phase is stable. The determined value of 48.3 kJ mol^-1 K^-1 is significantly higher than values published by other authors. At lower temperatures the hydrogen uptake is connected with a phase transformation from the hep α- to the bcc β-phase. The spatial phase distribution and the hydrogen concentrations in the two phases were analysed.