Addition effect of chloride salt for soil decontamination by cesium free mineralization

Shimoyama, Iwao   ; Honda, Mitsunori   ; Kogure, Toshihiro*; Baba, Yuji  ; Yaita, Tsuyoshi; Okamoto, Yoshihiro  

We study radioactivity concentration of contaminated soil in Fukushima to examine the effectiveness of cesium free mineralization (CFM) and analyze structural change of the soil using X-ray diffraction (XRD). CaCl or KCl was added to the soil and heated in air or under low-pressure conditions. In the case of CaCl, decontamination ratio Rd showed similar tendency for both air and low-pressure heating, and we found that Rd reached to 97% after heating at 790C. XRD analysis showed that basal reflection peaks of clay minerals in the soil disappeared and quite different XRD patterns were observed between air and low-pressure heating treatments. These results indicate that CFM is effective for decontamination of actual Fukushima soil, and product by CFM largely depends on pressure condition during heating. On the other hand, Rd was higher for low-pressure heating than for air heating with KCl, and XRD showed that clay minerals remained after the heating treatment. This means different mechanisms of Cs removal from contaminated soil exist for heating treatments with KCl and CaCl.