Numerical analysis of the galvanic coupling in the shadow corrosion of zirconium alloy

Shadow corrosion of Zircaloy cladding in a boiling water reactor is numerically studied using finite elements modelling. The Laplace equation is solved using boundary conditions determined by an empirical law of the anodic oxidation of Zircaloy. The effects of the distance between electrodes, the electrolyte conductivity and the parameters relating to oxido-reduction reaction are specifically investigated. It is shown that if the conductivity and reaction rates at the electrodes are high enough, the level of shadow corrosion increases drastically. A particular attention is given to the interfacial resistance induced by the potential drop in the oxide film.