A series of electrochemical experiments were conducted to investigate the effect of dissolved oxygen, pH and Cl 2 on the corrosion rate of reinforcing steel of geological disposal facility saturated with groundwater. It was found that the corrosion rate was proportional to the concentration of Cl 2 and dissolved oxygen which are known as a corrosive agent and an electron acceptor, respectively. The pH level also strongly influenced the corrosion rate of the reinforcing steel. Under the pore water conditions of concrete structure of geological disposal facility, i.e. pH of 10-12 and dissolved oxygen of 1 mg L 21 , the corrosion rate of reinforcing steel was determined to be in the range of y10 28 to y10 29 m/year. The corrosion rates were higher than those estimated from an empirical model based on the diffusion of dissolved oxygen.

A concrete silo plays an important role in subsurface low-and intermediate-level waste facilities (LILW) by limiting the release of radionuclides from the silo geosphere. However, due to several physical and chemical processes the performance of the concrete structure decreases over time and consequently the concrete loses its effectiveness as a barrier against groundwater inflow and the release of radionuclides. Although a number of processes are responsible for degradation of the silo concrete, it is determined that the main cause is corrosion of the reinforcing steel. Therefore, the time it takes for the silo concrete to fail is calculated based on two factors: the initiation time of corrosion, defined as the time it takes for chloride ions to penetrate through the concrete cover, and the propagation time of corrosion. This paper aims to estimate the time taken for concrete to fail in a LILW disposal facility. Based on the United States Department of Energy (DOE) approach, which indicates that concrete fails completely once 50% of the volume of the reinforcing steel corrodes, the corrosion propagation time is calculated to be 640 years, which is the time it takes for corrosion to penetrate 0.640 cm into the reinforcing steel. In addition to the corrosion propagation time, a diffusion equation is used to calculate the initiation time of corrosion, yielding a time of 1284 years, which post-dates the closure time of the LILW disposal facility if we also consider the 640 years of corrosion propagation. The electrochemical conditions of the passive rebar surface were modified using an acceleration method. This is a useful approach because it can reduce the test time significantly by accelerating the transport of chlorides. Using instrumental analysis, the physicochemical properties of corrosion products were determined, thereby confirming that corrosion occurred, although we did not observe significant cracks in, or expansion of, the concrete. These results are consistent with those of Smartet al., 2006 who reported that corrosion products are easily compressed, meaning that cracks cannot be discerned by eye. Therefore, it is worth noting that rebar corrosion does not strongly influence the hydraulic conductivity of the concrete.