Proposition of Cs free mineralization for reduction and reuse of contaminated soil

Shimoyama, Iwao   ; Honda, Mitsunori   ; Kogure, Toshihiro*

The decontamination method has not been established for soil contaminated with radioactive Cs. We adopted weathered biotite (WB) which sorbed non-radioactive Cs as a model contaminated soil and applied heating treatment to the WB at 700C under a low pressure condition of 14 Pa with NaCl-CaCl mixed salt. X-ray fluorescence analysis showed that almost all Cs and K were removed from the sample at 700C and Ca became dominant with temperature. X-ray diffraction spectra largely changed after the heating treatment indicating some phase transition from WB. Transmission electron microscopy analysis clarified that augite was the dominant product after the heating treatment at 700C. These results suggest a model that Ca derived from the mixed-salt induced the formation of augite, and that K and Cs were eliminated from the product as these large-size cations cannot constitute augite. Based on this model, we propose Cs free mineralization which can achieve decontamination and reuse of soil in Fukushima.