The properties of metal corrosion, such as the corrosion rate and corrosion expansion rate, are key factors for assessing the long term performance of the subsurface disposal system. In this study, transient changes in pH were first simulated using a finite difference computer code. In the second step, the consumption times of the residual oxygen in the facility after the backfill were calculated. Finally, the supply of dissolved oxygen in the groundwater to the engineered barrier and the corrosion amount resulting from it were estimated. A high pH of around 12?5 would persist at least for 105 years inside the low permeability layer (LPL). In addition, the results suggest that the rate of oxygen supply in the form of dissolved oxygen in the groundwater was very small due to the restriction of mass transport by the LPL and the low diffusivity layer. Thus, the environment in which aerobic corrosion extremely limited was found to be of long duration. This strongly suggests that, for assessing the long term performance of the engineered barrier system, anaerobic corrosion will have to be evaluated carefully.

This study was conducted in order to clarify the long term corrosion behaviour of containers made of carbon steel. Natural immersion crevice corrosion tests were carried out for 360 days in an alkaline and reducing environment using a combination of materials including carbon steel and welding materials or bolts. In addition, potentiostatic crevice corrosion tests were carried out for 90 days. In both tests, there was no evidence to suggest localised corrosion in the different kinds of metal contact parts, including carbon steel, welding materials and bolts. It was also recognised that crevice corrosion was less likely to be generated on disposal container materials. From these experimental results, it is believed that the possibility of localised corrosion is extremely low if the environment around the carbon steel container is maintained under highly alkaline and reducing conditions.