摘要：After the Fukushima Daiichi nuclear power plant accident, a large region of northeastern Japan was contaminated by radio-Cs (r-Cs). Contaminated soil and incineration ashes are generated through decontamination processes and daily human activities, respectively. To reduce the volume of such substances, several kinds of pyroprocessing techniques have been developed. R-Cs is thought to be trapped within aluminosilicates. With the addition of Ca to these compounds, alkali metals may be readily removed. Next, Cl is added and the alkali metals are volatilized in the order of Cs > K > Na. On the basis of this estimation, the highest Ca content is expected to produce the best conditions for the removal of Cs. Calcium silicate and aluminate with the highest Ca concentration are found in Portland cement. To understand the mechanism of Cs volatilization, the effect of the Ca/(Si+Al) ratio on the ratio of Cs remaining is introduced on the basis of data from the literature. A high-efficiency Cs removal process in cement is also investigated using a small scale rotary furnace for real contaminated soil and ashes, and by pilot-scale experiments with model soil. Additionally, through detailed experiments using pollucite—a cesium aluminosilicate—Cs removal behaviors were found to correspond to phase change, depending on the Ca/Si and Cl/Cs ratios. At high Ca/Si ratios, even without adding Cl, a significant amount of Cs could be removed. Potassium existing in or added to the initially contaminated samples facilitated Cs removal such that Cs was reduced to an undetectable level even without the addition of Cl.
