Rate-limiting step of the deuterium desorption kinetics from Zircaloy-4 oxidized in PWR light primary water

Abstract This study aims at identifying the rate-limiting step and quantifying the kinetic constants of diffusion and deuterium desorption from a Zircaloy-4 alloy oxidized in light primary water. Secondary Ion Mass Spectrometry deuterium concentration profiles in ZrO2, combined with finite elements simulations, reveal that the deuterium desorption from an oxidized Zircaloy-4 alloy is kinetically controlled by a mixed regime of surface recombination and diffusion in the oxide in the 600 K–1000 K temperature range. At lower temperatures, desorption is controlled by the deuterium diffusion in the oxide layer whereas at higher temperatures the surface recombination reaction dominates.