It is predictable from previous studies that radiocesium hardly migrates into surrounding soils and groundwater from soils contaminated by the accident at Fukushima Daiichi Nuclear Power Station if they are buried and covered with clean local soils. This study demonstrated the prediction by performing in-situ migration experiments over a year in a public park in Miho, Ibaraki prefecture and in two public parks in Misato, Saitama prefecture. Contaminated surface soils were gathered and buried at a depth range of 0.3 ～ 1.0 m or at 0.3 ～ 1.3 m and covered with clean local soil layer of 0.3 m, and were sprinkled with water to accelerate the radiocesium migration. Migration of radiocesium was not observed from radiometric analyses of boring cores and soil water samples. Laboratory column and sorption experiments revealed that the radiocesium hardly leaches out of the soil and even if it leaches out from the contaminated soil, radiocesium is sorbed on surrounding soils and hardly migrates through the soil layer. Simulation of Cs-137 migration for 100 years by an advection-diffusion model showed that Cs-137 migrates slightly and decays out in the contaminated soil.

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  This study discussed the formation and stability of calcium-silicate-hydrate (C-S-H-gel) in the highly saline water. From the experimental results, the formation of C-S-H-gel was not affected by NaCl concentration with up to 600 mM. In addition, Raman spectrum analysis showed that the polymerization degree of silicate chain in the structure of C-S-H-gel was not remarkably affected by the concentration of NaCl. These mean that, even in the condition saturated with highly saline water, C-S-H-gel forms are stable.

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  Assessment of the geological environment for the long term safety of geological disposal systems for high-level radioactive waste requires consideration for any phenomenon resulting in cumulative change to the geological environment at the regional scale. Groundwater pressure changes induced by earthquakes, for example, are one of the phenomena to be considered. Groundwater pressure changes induced by earthquakes have been observed during long-term monitoring carried out by Japan Atomic Energy Agency in the Tono Area, Gifu. In this paper, the observations of groundwater pressure change induced by earthquakes are summarized. In addition, an impact on groundwater flow conditions induced by earthquakes is discussed. As a result, it is inferred that influence of groundwater flow condition induced by the three earthquakes, Tokachi-oki Earthquake in 2003, the off the Kii Peninsula Earthquake in 2004 and the Suruga Bay Earthquake in 2009, are temporary. On the other hand, the groundwater pressure changes after the 2011 off the Pacific coast of Tohoku Earthquake seem different from those by the three earthquakes and it is necessary to continue the observation of the groundwater pressure. In addition, this paper shows that it is important to focus not only the change of groundwater pressure but also the change of the hydraulic gradient and hydraulic permeability in evaluating the long-term stability of groundwater flow condition.

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  A simulation test was done for confirming quantitative values of ratio of Cl-36 activity sorbed on metal specimen surface to Cl-36 concentration in liquid solution, i.e. sorption factor of Cl-36 on stainless steel materials etc. in LLW generated from nuclear power plant. The sorption factor is very small and the dependence of chemical condition of liquid phase, corrosion state of metal surface and difference of metal material on the sorption factor was not observed significantly.

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