The UO2-Zircaloy chemical interaction

Existing experimental data on the interaction of uranium dioxide and Zircaloy are analyzed with a model that accounts for the formation and growth of three corrosion layers between the oxide and the metal. The kinetics of the process are governed by diffusion of oxygen and uranium in the five-zone system with chemical equilibrium at four interfaces. Three of the zones consist of two elements and are treated by conventional scaling theory. Transport of all three elements (Zr, U, and O) occurs in the remaining two zones, one of which consists of two coexisting phases. Modeling of the system results in product layer growth rates which are in good agreement with the experimental results at 15000C, which is the only temperature that both kinetic and thermodynamic information is available for application of the theoretical model. (orig.)