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Kōtō-ku, Japan

Kishi H.,Tokyo Electric Power Company | Kakue T.,Tokyo Power Technology Ltd. | Komine H.,Waseda University | Murakami S.,Ibaraki University
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

Precise evaluation of the permeability in a dam foundation is extremely important for reasonable dam foundation treatment. The Lugeon test of permeability assumes a laminar flow around a test section in a test hole. However, it is often pointed that the flow around the section is usually a turbulent flow. In such cases, the permeability is underestimated. To investigate this matter further, laboratory tests of permeability were conducted on single cracks of boring cores. In this experiment, water was used to evaluate the transfer condition from a laminar flow to a turbulent flow. Results show that the critical Reynolds numbers were on the order of several hundreds, which is much lower than the standard number of 2,000 for the flow between a pair of parallel plates. Subsequently, the progressive conditions of the turbulent flow in the Lugeon tests were evaluated using a new theoretical equation representing the relation between the injection pressure and flow rate under laminar and turbulent conditions on a radial flow model between parallel plates. The outcome indicated that the turbulent flow was highly developed in the tests. Based on the results presented above, the flow condition in a rock mass during grouting was evaluated. The evaluation model was the previous model expanded for use with non-Newtonian fluids. Using this model, a new injection method was proposed for grout particles to penetrate to the target area, and then subsequently settle and block up cracks from the far side toward the near side around a borehole. Using this method, the grout-flow condition is kept turbulent with high carrying power in the interval of penetration to the target area. Then the condition becomes laminar for settlement. The feasibility of this method was evaluated using results of calculations done with the model. © 2014 by Japanese Committee for Rock Mechanics. Source


Parajuli D.,Japan National Institute of Advanced Industrial Science and Technology | Takahashi A.,Japan National Institute of Advanced Industrial Science and Technology | Tanaka H.,Japan National Institute of Advanced Industrial Science and Technology | Sato M.,Fukushima Agricultural Technology Center | And 3 more authors.
Journal of Environmental Radioactivity | Year: 2015

Cesium extraction behavior of brown forest type soil collected from paddy fields in Fukushima nuclear accident affected areas was studied. In nitric acid or sulfuric acid solutions at elevated temperature, the concentration of Cs in soil available for extraction, m0, has been estimated on the basis of modified canonical equation and the equations derived from assumed equilibria. With the variation in temperature, mixing time, and soil to solvent ratio, the observed m0 values in 0.5M acid solution ranged between 1.5 and 2.9mg cesium per kilogram of soil. By increasing the acid concentration to 3M, the value of m0 could be sharply increased to 5.1mg/kg even at 95°C. This variation in the extractable concentration of cesium with the parameters signifies the existence of different binding sites in the soil matrix. The results observed for uncontaminated sample could be reproduced with the radioactive cesium contaminated sample belonging to the same soil group. © 2014 Elsevier Ltd. Source


Parajuli D.,Japan National Institute of Advanced Industrial Science and Technology | Kitajima A.,Japan National Institute of Advanced Industrial Science and Technology | Takahashi A.,Japan National Institute of Advanced Industrial Science and Technology | Tanaka H.,Japan National Institute of Advanced Industrial Science and Technology | And 7 more authors.
Journal of Environmental Radioactivity | Year: 2016

Cs decontamination efficiencies of the composites of iron hexacyanoferrate nanoparticles were investigated in comparison with commercial Prussian blue and natural zeolite. In pure water solution, the adsorption rate varied with sizes. In ash extract, where Cs adsorbing ability of zeolite was sharply dropped due to its poor selectivity, the impact of coexisting ions was negligible for FeHCF. FeHCF-n11, having the finest primary and secondary particle size, resulted the highest distribution coefficient, which was comparable to the high efficiency analogues, CoHCF or NiHCF. This observation suggested the possibility of preparing the high performance FeHCF by particle size and composition adjustment. FeHCF nanoparticle in bead form was tested for the removal of radioactive Cs in pilot scale. Due to larger secondary particle size, pronounced effect of solution temperature on the Cs adsorption kinetics on FeHCF bead was observed. Adjusting the mass of the adsorbent for the given solution temperature is recommended for achieving high decontamination rate. © 2015 Elsevier Ltd. Source

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