Effect of a pre-oxidation on the hydrogen desorption from Zircaloy-4

•The oxide scales shifted the hydrogen desorption towards higher temperatures.•The oxide layer is a barrier to the hydrogen release from the alloy.•The oxide layer dissolution is simulated by finite elements.•The dissolution kinetics of the oxide layer controls the hydrogen desorption. During the transport of nuclear spent fuel, part of the tritium formed by ternary fission in core of nuclear reactors is susceptible to desorb from the oxidized cladding. This study aimed at identifying the rate-limiting step in the hydrogen desorption process from pre-oxidized Zircaloy-4 specimens. Controlled-thickness oxide scales shifted the hydrogen desorption from the alloy towards higher temperatures during a temperature ramp under vacuum. Scanning electron microscopy observations and finite elements modelling of the oxide layer dissolution led to the conclusion that, in such conditions, hydrogen desorption from the alloy was controlled by the oxide dissolution kinetics.