Abstract
In order to apply thermal plasma melting method to treatment of low level miscellaneous solid wastes, it is essential to understand effects of treatment conditions on the migration rate of Cs to the molten slag because Cs is an important nuclide for evaluating radioactivity in the waste before disposal. It was found in our previous studies that the effect of the waste composition on the migration rate of Cs could be evaluated by using basicity under the same heating condition. To establish a method for evaluating the effect of the melting conditions such as waste mass and heating power on the migration rate of Cs, the vaporization behavior of Cs is discussed by measuring the temporal change of molten bath form and concentration of Cs in the molten slag. The temporal change of concentration of Cs in the molten slag was expressed by a first-order type reaction rate formula when the samples were melted completely. The concentration of Cs in the molten slag were calculated from the rate constant and the result of temporal change of the molten slag form using the rate formula established from the molten bath formation model in a batch melting process. The calculated values were in good agreement with the experimental results. We found that the migration rate of Cs to the slag layers depends on the vaporization rate constant of Cs and the melting rate of the waste components forming slag. This result suggests that the effect of the melting conditions such as amount of inorganic waste materials and heating power on the migration rate of Cs to the slag layer can be evaluated by using the melting rate of the waste components forming slag.
