Effect of Temperature on Electrochemical Properties of Zircaloy-4 by AC Impedance Spectroscopy - 19305

The evaluation of waterside corrosion behavior of zirconium alloys in the disposal environment is considerable subject. The geological disposal environment is considered as 'low temperature' about 30 deg. C - 80 deg. C, which corrosion rate of Zircaloy-4 is very slow. On the other hand, at the 'high temperature' during normal operation temperature of commercial reactors around 300 deg. C, rich studies about out-of-pile waterside corrosion rate of zirconium alloys have been accumulated by the analyzing weight gain or oxide thickness obtained as a result of the autoclave test because of evaluable corrosion rate. There, in the intermediate temperature - 120 deg. C, 150 deg. C, and 180 deg. C - between low temperature and high temperature, in order to simulate the early stage of corrosion, Zircaloy-4 oxide films with thickness of 10 nm and 30 nm were formed, and the evaluations about the properties of the oxide films were tried by AC impedance spectroscopy. As the result, it is suggested that a dense oxide film which has resistance against corrosion may be formed with a lower corrosion temperature. And also, since the measurement of weight gain with corrosion has been considered as the main method for evaluation of corrosion, AC impedance spectroscopy for Zircaloy-4 is suggested to an effective method for in-situ measurement of property and thickness of Zircaloy-4 oxide film. (authors)