Abstract
The aim of this study is clarifying the leaching behavior of hardly-soluble cesium contained in bottom ash and the factor affecting its leaching behavior. For this purpose, pH dependence test, determination of the Cs content by different particle size and pH dependence test of different particle size fraction were conducted. incineration bottom ashes that was artificially created to contain cesium in high content was used. In pH dependence test, solvents were prepared by using nitric acid to be target pH from 1.9 to 10.8. As the results, leaching amount of hardly-soluble cesium increased together with silicon and aluminum along with decrease of pH. Hardly-soluble cesium combining with aluminosilicate or existing in glassy amorphous phase was deemed to be leached out by the exposure to strong acid. However, the low pH performed in the test never occur in real incineration ashes because pH of ashes is generally high and pH of ash that passed for a long period of time is reported to be almost 8.5. Leaching ratio of cesium is only 2 to 3% at such pH. Content of Cs in each particle size was not different and difference of leaching behavior were not observed either.
