Liquid paraffin was added to 3 kinds of smectite dispersions containing different amount of salt to prepare emulsions. Stable emulsions were obtained when the smectite particles aggregated to make the dispersions turbid or almost were segregated with salt. Smectite and cationic cellulose were mixed and then the mixtures were investigated as salt tolerance thickener and emulsifier. The smectite-cationic polymer complex could act as thickener even if the complex dispersion contained 3 wt% of NaCl. The complex dispersion viscosity increased as the molecular weight of the added cationic polymer increased. Finer droplet emulsion was obtained with smectite-cationic cellulose complex containing 3wt% NaCl compared to the smectite emulsion.

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It is essential to make the effective decontamination and to reduce the amount of the contaminated materials with radionuclides in the areas damaged from the Fukushima Daiichi nuclear disaster. The Clay Science Society of Japan (CSSJ) has made the great efforts for so-called "Fukushima Problems" as one of the scientific groups for clays and clay minerals. A review is given of the contributions against the problem from CSSJ itself and also the interested members in CSSJ joining the interested research projects. We would like to realize again the important role of CSSJ for the problems considering the results in these projects.

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The accident at the Fukushima No.1 Nuclear power plant of Tokyo electric power company.inc has resulted in the diffusion of radioactive substance and seriously affected agricultural production. The Fukushima Agricultural Technology Centre has clarified the effects on the farming land and crops and has achieved a certain level of success through approaches to research on radioactive substance removal/reduction and absorption suppression.

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Josome business is advanced at a radioactivity polluted area by an accident of Tokyo Electric Power Daiichi Fukushima nuclear power plant. A resident explanatory meeting was frequently put into effect in an accident, and necessity of refuge, refuge place securement and the related guarantee were argued. Development of decontamination technique and securement of place where temporary putting does decontamination waste were advanced at the same time, but after all the time I don't advance easily roughly followed resident anxiety without knowledge to radioactive materials. After that there are a local community as well as chipping a bearer of rehabilitation and danger of economy, cultural disappearance and desolation at the return difficult area and the resident restriction area where I change and also hit heavily-polluted area by the inside, and a problem as well as passage in time are difficulty which returns to a village.

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Although more than four years have passed after the accident at the Fukushima-Daiichi nuclear power plant, the state of radioactive cesium, which is the main source of the high radioactivity in the environment of Fukushima, is not well understood yet. To advance this situation, we tried to specify radioactive soil particles using IP autoradiography and electron microscopy. As a result, the radioactive soil particles were classified into three types from their morphologies and chemical compositions: (1) conglomerates of fine clay minerals, (2) organic matter containing clay mineral particulates, and (3) weathered biotite with a platy shape originated from granite. The weathered biotite is actually a biotite-vermiculite mixed-layer mineral, forming a porous structure with well-developed cleavage, and kaolinite filling the cleavage spaces. It was indicated that radioactive cesium is located uniformly in the weathered biotite, rather than concentrated around the edges of the platy shape.

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Cesium sorption and desorption of clay minerals (montmorillonite, beidellite, nontronite, weathered biotite, rectorite and illite) were investigated by consecutive sorption-desorption (CSD) experiments. In batch sorption experiment, two solutions with different Cs concentration (10^<-3> and 10^<-7> mol/L) were used. In batch desorption experiments, Cs sorbed samples in sorption experiments were treated 5 times with 1 mol/L ammonium acetate solution. In the case of CSD experiments using 10^<-3> mol/L Cs solution, the exchangeable cations (Na, Ca and K) in the clay samples affected to the sorption ratio of Cs, and this effect depended on the type of clay mineral. The desorption ratios of untreated, Na-exchanged and Ca-exchanged weathered biotite ranged from 23 to 33%, while that of other samples was over 80%. In the case of CSD experiments using 10^<-7> mol/L Cs solution, the sorption ratio of montmorillonite was smaller than that of the other clay samples. In desorption experiments, more than 10^<-9> mol sorbed Cs remained in 1.0 g of the sample after 5 extraction times. These results indicate that all examined clay samples are able to strongly adsorb Cs with a capacity of more than 10^<-9> mol/g.

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After the accident in the Fukushima Daiichi Nuclear Power Station caused by the 2011 Tohoku earthquake and tsunami, the decontamination of radioactive cesium spread from the Nuclear Power Station to all over the Fukushima prefecture has still been continued constantly. Moreover, the huge amount of radioactive waste typified by removed contaminated soil have been increasing on a daily basis. It is expected that the contaminated soil encumbers the acceptable amount of the interim storage facility. Therefore, various kinds of volume reduction methods are tackled. The classification method is one of feasible prospects, and is required to optimize. This study focused on the distribution of radioactive cesium in the contaminated soil for improving the volume reduction method by the soil classification. Clay minerals are reported to specifically adsorb cesium. The wet classification test proved that the fine particles classified from the actual contaminated soil in Fukushima clearly accumulated radioactive cesium, and contained clay mineral. The amount of radioactive cesium exceeding tolerance level still remained in the large particles over the size of 0.5 mm. As a result of the observation of particles the size of 0.5 mm 4.75 hand-picked by the difference in optical characters such as color and shape, particle groups showed differences of radiation quantity and composition of minerals. Especially, organic matters and soil aggregation showed high radiation quantity. Furthermore, the group of tabular particles including clay minerals, such as mica and vermiculite, showed demonstrably highest radiation quantity among particle groups. For the future, it is suggested that the classification method for the volume reduction should be improved with a focus on the clay minerals mineralogically, not mechanically.

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Melting technique is one of useful high-temperature treatments carried at 1300-1400℃. Using the technique, Cs can be separated in high efficiency from different solids degreasing their volume significantly. In our previous laboratory melting test, a high Cs volatilization ratio had been obtained for various solid wastes containing non-radioactive Cs. Therefore, in this study, we conducted a demonstration plant test (3 t/day) for soil, biomass incineration ash, etc. containing non-radioactive Cs. As a result, regardless of the kind of solid sample, Cs volatilization ratio increased by the addition of CaCl_2 even in the plant scale test. The Cs volatilization ratio in the presence of combustible vegetation was higher than that without the combustibles. Increasing the amount of additive reagent and vegetation achieved 99.9% of the Cs volatilization ratio. Next, we conducted a laboratory melting test for soil containing radioactive Cs. As a result, the volatilization ratio of radioactive Cs with the addition of CaCl_2 was the almost same as that of non-radioactive Cs, this shows the influenced factor by the addition of CaCl_2 was not the volatilization amount of Cs but the gas-liquid distribution ratio of Cs. Furthermore, we carried out a feasibility study on applying the melting technique to the treatment of decontamination wastes. As a result, it was estimated that total 30 years' cost (from intermediate treatment to final disposal) was the lowest in the case of applying the melting technology to the treatment of only fine soil and the ash of combustibles.

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