抄録
In March of 2011, radioactive pollution spread out over the around Fukushima No. 1 Nuclear Power Plant. The atmosphere and soil have contaminated with radio isotopes in the area. It is known that ultrasound can wash out the contamination. It can also extract the component. To contribute the elimination of radioactive cesium from the soil contaminated ultrasound treatment was carried out using an ultrasonic cleaner. Ultrasound treatment provided significant benefits over the conventional chemical extraction. Decrease in radio activity was observed after ultrasonic treatment for 1 hour which had three cycles of continuous waves for 20min.Washing water was exchanged for fresh water at each cycle. Fine chips were suspended in drain water. In particular, the first drain had the most concentration of suspension. After few hours, the clarity of the solution increased and fine chips accumulated on the bottom of a stock bottle. Radio activity for the solution was the similar to that for non-contaminated water. Thus, the chips were thought to peel with radio isotopes from the surface of soil and most of soil remained had just a little radio activity. On the other hand, high level removal was also achieved by solvent extraction. In this chemical treatment, however, a strong mineral acid solution for solvent, additives, and longtime heating were needed in order to increase efficiency.
