Estimation of the Corrosion Thickness of a Disposal Container for High-Level Radioactive Wastes in a Wet Bentonite

The surface alteration and mass loss of iron and copper specimens have been investigated to under- stand the corrosion behavior of candidate materials for a metal container for the disposal of high-level radio- active wastes in a disposal condition. For the corrosion experiments, iron and copper specimens were put into the bentonite wetted with the two different groundwaters in order to compare the corrosion result in a synthetic groundwater with that in a natural groundwater. After the corrosion experiments, Cu2O was formed on the sur- face of the copper specimen and a dark green corrosion product on the surface of iron specimen. Experimental equations for the estimation of the corrosion thickness of iron and copper were induced as a function of corrosion time based upon the assumption that the mass loss of a specimen uniformly occurred over the whole surface of the specimen as follows: Xiron = (0.26 ± 0.08)⋅t (0.64 ± 0.05) for iron and Xcopper = (0.063 ± 0.07)⋅t (0.32 ± 0.02) for copper. From these two equations, the uniform corrosion thicknesses for iron and copper after 1000 years in an anaerobic disposal condition are estimated as 0.3∼2.4 mm and 2.6∼5.7 µm, respectively.