Fixing Radio-Cesium(Cs-137) in Soil with Vermiculite in Fukushim.

Tsunami caused by the 2011 earthquake in Japan damaged the Fukushima Daiichi Nuclear Power-Plant, and a large amount of radioactive materials was released into the atmosphere. The fallout of the, radioactive materials contaminated the ground. Cesium-137, among the radioactive materials, is an important substance in terms of a decontaminating procedure because of its relatively long half- life, 30.2 yrs. In this study we investigated whether mixing vermiculite removed and fixed more Cs-137 from contaminated soil, mostly a granite origin. Soil sample was mixed with distilled water or 1 M KCl solution and agitated for Q min, then filtered. Gamma ray spectra of the oil sample and the leachate were measured with a Ga spectrometer. There was little evidence that the vermiculite removed and fixed Cs-137 from the soil. We further carried out a standstill experiment with leaving the mixed samples for 1,2,3,4, and 5d after agitation.The concentration of Cs-137 in a leachate from the sample of 5 dafter standing decreased to about a half of those from the leachates of other samples. The results showed vermiculite removed and fixed Cs-137 from the soil but require at least 5 d.