High-Temperature Oxidation of a Sponge-Based E110 Cladding Tube Material: Weight Gain and Reaction Layer Kinetics

High-temperature oxidation of WWER fuel cladding under loss-of-coolant accident conditions represents a significant problem and an issue of ongoing study. A study of oxidation kinetics under high-temperature steam oxidation was carried out on a sponge-based E110 cladding tube material in as-received state and exposed to a temperature range between 600°C and 1300°C. Metallographic evaluation of the samples was used to determine the analytical dependencies of the processes of the oxide layer and the oxygen stabilized alpha-zirconium layer formation.

The formation of this oxide layer and the layer under the oxide (oxygen stabilized alpha-zirconium) was usually considered to follow a parabolic rate law (e.g., Cathcart-Pawel for Zircaloy, and Solyany for iodide/electrolytic E110), however, the recently performed UJP PRAHA a.s. (UJP) experiments showed different kinetics for oxide layers in the whole temperature range between 600°C and 1300°C. The metallographic evaluation showed changing kinetics of oxide layer formation for several temperatures. Therefore, a new oxide layer formation kinetics, different from the parabolic law, was designed. The parabolic rate law was optimized for the oxygen stabilized alpha-zirconium, which is applicable in the temperature range between 950°C and 1300°C.

The UJP experimental database containing more than 1000 data values was compared with the newly developed UJP correlations and other available correlations for iodide/electrolytic E110 and Zircaloy alloys. The UJP correlation for weight gain kinetics was compared with experimental data from different laboratories. Finally, a statistical analysis of all tested correlations is provided.