Calculations of Oxidation Rates of Zirconium

The rates of oxidation for zirconium metal in oxygen are calculated using perfusive-precipitation modeling with the boundary conditions that: (1) there is no moving boundary and (2) metal matrix saturation is reached for oxygen solubility. The perfursive-precipitation model is a diffusion model with a chemical reaction. It uses Fick’s Second Law of Diffusion with an added sink term. The sink term is an overall second order reaction, first order with respect to each the dissolved oxygen and the metal. The stationary boundary condition is valid for the ductile zirconium as long as the expansion due to the reaction product formation does not cause metal failure or spalling. The metal matrix saturated condition implies an upper limit to the metastable solubility of oxygen In the zirconium metal and is approximated from the phase diagram. The calculated rates are compared to the rates listed in the literature. These calculated rates, using no variable parameters, are in good agreement with experimental data.