High-temperature oxidation of accident tolerant Cr-coated Zr alloy cladding: Model development and validation

In our previous studies of Cr-coated Zr alloy cladding, models for the oxidation and degradation of Cr coating and for the oxidation and phase transformation of Zr alloy have been established. On these foundations, oxygen flux models for Cr-Zr non-eutectic and eutectic conditions are developed in this paper, enabling a comprehensive simulation of the oxidation processes of Cr-coated Zr alloy. The models are validated through oxidation experiments under isothermal and temperature ramp conditions, showing good agreement with the experimental data. The models can effectively simulate the processes where, under non-eutectic conditions, oxygen atoms first dissolve into the prior β-Zr matrix after coating degradation, followed by the formation of α-Zr(O) and eventually ZrO₂. For conditions with eutectic reaction, model assumption of immediate complete coating failure could lead to overestimation of substrate oxidation extent at low heating rates. This prediction deviation decreases as heating rate increases.