In-situ studies of the oxide film properties on BWR fuel cladding materials

The corrosion resistance of Zirconium alloys is influenced by the electrical and electrochemical properties of the oxide films. This study searches correlations between these oxide films properties and the second phase particle structures and hydrogen contents of the alloys. The target is to improve capabilities to compare candidate fuel cladding products through experimental techniques. Three types of Zircaloy-2 specimens with the second phase particle sizes ranging from 0.049 μm to 0.174 μm and two specimens hydrided up to 1000 ppm of hydrogen were used in the experiments. The work consisted of electrochemical impedance spectroscopic, contact electric impedance and contact electric resistance measurements performed using the controlled distance electrochemistry arrangement in simulated BWR coolant conditions at a temperature of 300 deg C. The results obtained up to now do not enable discerning between the transport properties of the oxides formed on the different Zircaloy specimens. Alternative experimental methods are proposed for continued research efforts. (orig.)