Abstract
The accident at the Fukushima Daiichi Nuclear Power Plant resulted in a huge amount of radioactive cesium spreading widely. It is important to decontaminate the radioactive cesium and dispose the radioactive waste safely as soon as possible. The sorption properties for cement materials have already been investigated by several researchers. However, the studies on the mass transfer considering the time histories of moisture contents in the concrete under cyclic drying and wetting conditions are very few. Therefore, this study aims to investigate the cesium behaviors such as adsorption, penetration in the cyclic dying and wetting conditions, and leaching in mortar. As a result, it was observed that cesium was hardly adsorbed on cement hydrates as well as aggregates prepared in this study, while significantly adsorbed on zeolite. In addition, in mortar specimens processed with water saturation, 80％ of cesium existing in the whole area of specimens was soluble. On the other hand, in dried specimens, 80％ of existing cesium were soluble only in the inner area of the specimen, but in the surface area, 60％ of the penetrated cesium was soluble in the surface. We thought that large amounts of the cesium were fixed as insoluble at the surface, and it was caused by carbonation of the specimen. Furthermore, it is easy to leach cesium from mortar, so that cesium easily transported in the specimen under cyclic drying and wetting condition.
