Decontamination test of radioactive contaminated soil by Cs-free mineralization with alkaline chlorides

Shimoyama, Iwao   ; Kogure, Toshihiro*; Okumura, Taiga*; Baba, Yuji  ; Okamoto, Yoshihiro  

In this work, we examined Cs-free mineralization (CFM) for decontamination of Fukushima soil with four alkaline chloride additives below 800C in air and under low-pressure conditions. In the case of CaCl, radioactivity concentration largely decreased in both air and low-pressure conditions, and decontamination ratio reached to 97% at 790C. In the case of MgCl, we found a tendency that decontamination ratio was higher under low-pressure condition than in air and it was more than 99% after three cycles of heat treatments at 695C. KCl and NaCl reagents also showed similar tendency, and decontamination ratio reached to 93% and 97% for KCl and NaCl, respectively, after five cycles of heat treatments at 790C. Structural analysis of products clarified that heat treatments with CaCl and MgCl decomposed biotite which is the major Cs sorbent in the soil in Fukushima. On the other hand, similar decomposition was not observed when KCl and NaCl were used as additives. Based on these results, CFM was confirmed to be effective for soil decontamination, and we found that Cs removal process depends on the valence of metal ions as chlorides.