抄録
We propose a low-pressure sublimation method as a new dry method to remove radioactive Cs from clay minerals. To develop this method, we used thermogravimetric analysis (TGA), thermal desorption spectroscopy (TDS), and X-ray photoelectron spectroscopy (XPS) to study Fukushima vermiculite particles saturated and sorbed with nonradioactive Cs and heated in air and under low-pressure and high-vacuum conditions. The results of low-pressure TGA show a mass decrease due to Cs desorption, which is not observed for TGA conducted with the samples in air. The Cs desorption peak at 680℃ is confirmed by high-vacuum TDS. XPS measurements clarify that, on maintaining the samples at 800℃ for 3 min in high vacuum, approximately 40% of the Cs desorbs from the vermiculite. Furthermore, TDS results show that adding a mixed salt, NaCl-CaCl_2, shifts the Cs desorption peak by 180℃ to lower temperatures. These results demonstrate that the proposed method of low-pressure sublimation with added salts enables Cs decontamination of clay minerals at considerably lower temperatures than those in conventional dry methods.
