Characterization of soluble and insoluble radioactive cesium in municipal solid waste incineration fly ash

Soluble and insoluble radioactive cesium in municipal solid waste incineration fly ash were analyzed by X-ray diffraction and gamma-ray spectrometry. A total of 60% of soluble radioactive cesium was determined using the Tessier extraction method, and it was almost same extraction rate with Japanese leaching test No.13. In addition, chloride compounds such as halite (NaCl) and sylvite (KCl) showed same behavior with soluble radioactive cesium, therefore, soluble radioactive cesium existed as a chloride (CsCl) with water solubility characteristics. Almost insoluble radioactive cesium trapped into silicate of crystalline phase or amorphous phase was eluted by hydrogen fluoride treatment. Radioactive ¹³⁷Cs was released in three stages by heating treatment (untreated - 400 °C, 600 °C-800 °C, and 800 °C-1000 °C) according to decreasing amorphous content. The relationship between the concentrations of radioactive ¹³⁷Cs and amorphous phase exhibited good linearity (R = 0.9278). Insoluble radioactive ¹³⁷Cs was contained in inner part of the amorphous phase, and free radioactive cesium was determined from the concentration of the amorphous phase.