The relationship between the amount of oxidation and activation energy on the steam oxidation reaction of Zircaloy-4 cladding

Abstract Zirconium-based alloys are widely used as cladding material for light-water reactors, and in the case of a loss-of-coolant accident (LOCA), oxidation of the cladding by high temperature steam plays important roles in fuel rod failure and hydrogen generation during the accident. In this study, considering that the oxidation rate is related to the activation energy of the oxidation reaction, the relationship between the amount of oxidation and the activation energy of cladding oxidation by steam was investigated by thermogravimetry. The oxidation rate of the specimen decreased with increasing heating rate. The activation energy of oxidation was evaluated based on a non-isothermal kinetics theory. It was found that the activation energy of oxidation depends on the specimen weight gain. The activation energies showed constant values of ∼300 and ∼180 kJ/mol in the oxidation range between 30 and 120 g/m 2 and above 120 g/m 2 , respectively. A master curve which expresses the amount of steam oxidation of Zircaloy-4 cladding was formulated based on the activation energies obtained.