Review of Zircaloy Oxidation Kinetics and Models in Air and Air-Steam Mixture

Abstract

There are several events in CANDU® reactor where the fuel bundles may be exposed to air or air/steam mixture. The available experimental programs investigating Zircaloy oxidation in air and air/steam mixture and identifying the main characteristics of the oxidation kinetics in both environment are reviewed. The oxidation correlations that describe the oxidation kinetics in air and air/steam mixture are also identified and discussed. Sheath and fuel temperatures are expected to be higher for bundles exposed to air than for bundles exposed to steam due to the differences between Zircaloy oxidation kinetics and heat of reaction. Oxidation kinetics are generally faster and the heat of reaction is higher in air than in steam. Under accident conditions, sheath oxidation in air/steam mixture is more likely than oxidation in air. The ratio between air and steam in the mixtures plays a major role in determining the mass gain and the oxide thickness for a given sheath temperature and oxidation time.