Melting technique is one of useful high-temperature treatments carried at 1300-1400℃. Using the technique, Cs can be separated in high efficiency from different solids degreasing their volume significantly. In our previous laboratory melting test, a high Cs volatilization ratio had been obtained for various solid wastes containing non-radioactive Cs. Therefore, in this study, we conducted a demonstration plant test (3 t/day) for soil, biomass incineration ash, etc. containing non-radioactive Cs. As a result, regardless of the kind of solid sample, Cs volatilization ratio increased by the addition of CaCl_2 even in the plant scale test. The Cs volatilization ratio in the presence of combustible vegetation was higher than that without the combustibles. Increasing the amount of additive reagent and vegetation achieved 99.9% of the Cs volatilization ratio. Next, we conducted a laboratory melting test for soil containing radioactive Cs. As a result, the volatilization ratio of radioactive Cs with the addition of CaCl_2 was the almost same as that of non-radioactive Cs, this shows the influenced factor by the addition of CaCl_2 was not the volatilization amount of Cs but the gas-liquid distribution ratio of Cs. Furthermore, we carried out a feasibility study on applying the melting technique to the treatment of decontamination wastes. As a result, it was estimated that total 30 years' cost (from intermediate treatment to final disposal) was the lowest in the case of applying the melting technology to the treatment of only fine soil and the ash of combustibles.
