Evaluation of high-temperature oxidation behaviour of ATF claddings during severe accidents in nuclear power plants

This work aims to evaluate the oxidation behavior and kinetics of ADSS B#51 alloy in high-temperature air and to investigate the effect of the T-ramping rate on the kinetics of ADSS B#51. Using Thermogravimetric Analyzer (TGA), the high-temperature oxidation test was performed isothermally in air at 1000 °C, 1150 °C, and 1300 °C and for T-ramping tests at 1 °C/min, 4 °C/min, 40 °C/min. We estimated weight gains of the alloy in T-ramping condition and compared with measured value. It was concluded that the oxidation rates of the alloy during T-ramping were higher than those estimated by using parameters determined from the isothermal tests. In addition, surface oxide characterization using SEM-EDS demonstrated a complex surface oxide. Where the surface oxide and the oxide compositions were randomly distributed and not following any specific pattern. The findings showed that T-ramping oxidation kinetics parameters are in between the oxidation kinetics parameters of the steady-state region and transient region of isothermal oxidation, but closer to the transient region.