Corrosion monitoring of carbon steel in water saturation process of bentonite

Taniguchi, Naoki ; Kawasaki, Manabu*; Sugita, Yutaka ; Shibata, Masahiro ; Honda, Akira

Carbon steel is one of the candidate materials for overpacks of geological disposal of high level radioactive waste, and it is important to understand the corrosion behavior of carbon steel in repository environment. Initially, the buffer material composed of mainly bentonite will contain moisture depending on ambient humidity. The water content in buffer material will be increased with time due to the infiltration of groundwater. The oxygen in buffer material brought form the ground will be consumed by the reaction with minerals in bentonite and corrosion of overpack, and then low oxygen condition will be achieved around the overpack. The corrosion behavior of overpack will be varied with the change of environmental conditions during water saturation process of buffer material. In this study, a corrosion sensor was developed to monitor the change of corrosion behavior (corrosion potential and corrosion rate) with changing of the environmental conditions in buffer material. Using a prototype of the sensor, change of corrosion of carbon steel was monitored actually in buffer material in the process of saturation.