Water radiolysis and its effect upon in-reactor zircaloy corrosion

The well-known effects of dissolved oxygen and hydrogen in respectively increasing and reducing the corrosion rate of zircaloys irradiated in high temperature water have been attributed to changes in the course of water radiolysis. Computer simulation of the growth and decay of radiolytic species produced by β, γ and neutron irradiation of water at 250C and 3050C has been performed. In general, neutron irradiation leads to greater decomposition of water, and the effect of dissolved oxygen at 3050C is to markedly increase the concentrations of oxidizing radiolytic species. Correlation of zircaloy corrosion behaviour under such conditions with predictions of water radiolysis suggests that either HO2 of O2- are significant contributors to the corrosion enhancement phenomenon. Possible enhancement mechanisms are briefly discussed. (author)