Soil decontamination by heat treatments with chlorides under low-pressure conditions

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

More than 99% of radioactive Cs can be removed from soil by heat treatment at more than 1000C, however, its high cost inhibits application of this method. In this work, we attempted heat treatment with four kinds of chloride reagents under low-pressure condition to decrease processing temperature. Each reagent was added to contaminated soil and heat treatment was applied in air and under low-pressure conditions for two hours. In the case of CaCl, the difference in decontamination ratio was small for different pressure conditions and decontamination ratio reached to 95% at 790C. On the other hand, MgCl, NaCl, and KCl had higher decontamination ratios under low-pressure conditions than in air. When MgCl was added, decomposition and phase transformation of biotite in soil was facilitated under low-pressure conditions, and decontamination ratios at 695C were 40 and 90% in air and under low-pressure conditions, respectively. In the cases of NaCl and KCl, biotite remained after the heat treatments and Cs was removed through ion exchange. When NaCl was added, decontamination ratios at 790C were 15 and 94% in air and under low-pressure conditions, respectively. Based on these results, we propose heat treatment with sea water salt as a reactant.