Abstract
In the restoration from the Eastern-Japan Great Earthquake and the following accident of Fukushima-Daiichi nuclear power plant, the treatment and disposal of a large amount of wastes and excavated soils is one of the most important problems. In this study, the feasibility of barrier materials of coastal disposal facility for wastes and soils contaminated by radio-active cesium is discussed. Assuming the initial concentration of radioactive contaminants 100,000 Bq/l, 4 m thick clay barrier was designed and analysed. The analyses revealed that the hydraulic conductivity of the clay barrier needs to be kept below 5.0×10-10 m/s to avoid the leachate of contaminants below the environmental safe limits. Therefore, a series of laboratory experiments was conducted on Tokuyama marine clay mixed with different proportions of bentonite to examine the engineering characteristics. The results of laboratory experiments showed that the hydraulic conductivity decreases with the addition of bentonite in the soil mixture. The performance on adsorption of clay mixture was measured by batch test and permeability test. The permeability test results showed that the adsorption properties were achieved by adding the bentonite to the Tokuyama marine clay.
