IMPROVEMENT OF INSOLUBILIZATION EFFICIENCY OF CESIUM IN FLY ASH BY ALKALI FELDSPAR USING ROTARY KILN

Abstract

 At present, to reduce the volume of decontamination waste, thermal treatment is carried out. In the thermal treatment, cesium (Cs) is volatilized and separated, resulting in fly ash containing much radioactive Cs. Cs in this fly ash is a chloride and is soluble. For safe final disposal, it is preferable that Cs in fly ash is insoluble. In this study, applying the mechanism that alkali feldspar makes Cs insoluble under heating conditions, whether the efficiency of insolubilization of Cs in fly ash improves was investigated by using rotary kiln. Indian feldspar, fly ash, and cesium chloride were mixed and heated at 700°C in a rotary kiln. No effect of rotating speed on Cs insolubilization was observed. After heating at 4 rpm of rotating speed and 700°C of temperature for 15 hours, 99% of the added cesium became insoluble. Even the addition ratio of Indian feldspar is reduced to about 80% of the amount of fly ash, by heating the mixture for 15 hours, 96% insolubilization of Cs was achieved.