The Effect of chloride additives on soil decontamination by cesium free mineralization

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

We examined decontamination of radioactively contaminated soil in Fukushima using cesium free mineralization (CFM). Radioactivity concentration was measured by an NaI detector before and after heat treatments in atmosphere and under low-pressure condition with CaCl or KCl additives. Without additives, decontamination ratios were about 5 and 20% for heat treatments in atmosphere and low-pressure conditions, respectively. With CaCl additive, similar decontamination ratios were observed for atmosphere and low-pressure heating, and it reached to 97% at 790C. X-ray diffraction analysis showed that clay minerals in the soil disappeared after the heating and products depended on the pressure condition during heating. With KCl additive, higher decontamination ratio was observed for heating under low pressure than in atmosphere, and it reached to 83% at 790C. Because clay minerals remained after the heating with KCl, we consider that most Cs was removed through ion exchange. These results clarified that CFM is effective for actual soil in Fukushima and that Cs removal process depends on the reagent as additives.