Numerical modeling of oxygen diffusion in the wall thickness of Low-Tin Zircaloy-4 fuel cladding tube during high temperature (1100–1250 °C) steam oxidation

A new numerical tool has been developed by coupling the diffusion code “EKINOX” (Estimation Kinetics Oxidation) and the thermodynamic database “ZIRCOBASE” using TQ (ThermoCalc program interface). The aim of this tool is to calculate the oxygen diffusion during oxidation of Zr based alloys. The simulation results of the oxide growth kinetics and the induced oxygen diffusion profiles in the [1100–1250 °C] temperature range, at different times, are presented and compared to previous experimental results. An estimation of the diffusion coefficient in the α phase is deduced from this comparison. The results are discussed in comparison to previous models based on an analytical treatment and the influence of the choice of the thermodynamic data set on the final oxygen diffusion profile is explored.Finally, it is shown that the present modeling is able to predict quite accurately the “critical” oxidation time corresponding to the overall ductile-to-brittle transition of the high temperature (HT) oxidized clad.