Geotechnical sealing material for coastal disposal facility for soils and wastes contaminated by radioactive cesium

ABSTRACT

Safe disposal of wastes produced due to the process of decontamination in and around Fukushima No. 1 nuclear power plant is an urgent requirement. The purpose of this study was to develop a sealing material which can be used as an engineered barrier for a final disposal facility for the soils and wastes contaminated by radioactive cesium. The analyses conducted based on 4-m-thick sealing layer revealed that the hydraulic conductivity of the sealing material needs to be kept below 5.0 × 10⁻¹⁰ m/s to avoid the seepage of contaminants below the environmentally safe limits. Sealing material was developed using marine clay–bentonite mixture and the engineering characteristics were examined. The results of laboratory experiments showed that, with the addition of bentonite, the hydraulic conductivity equal to or less than 5.0 × 10⁻¹⁰ m/s was achieved when the effective consolidation stress is equal to or more than 27 kPa. From the tests for adsorption properties for cesium, it was found that the sealing material showed the significant capacity of adsorption for cesium in seawater. It was concluded that the construction of waste disposal facility on the sandy seafloor is feasible using the sealing layer proposed in this study.

KEYWORDS:

• Adsorption
• contaminated soil
• hydraulic conductivity
• marine clay
• radioactive cesium
• sealing layer
• waste disposal facility