Hydraulic characteristics of sedimentary deposits at the j-parc proton-accelerator, japan

Hydraulic characteristics of sediments were investigated at J-PARC for the purpose of site characterization in relation with the construction of Japan's largest proton-accelerator. A total of 340 samples extracted from 9 exploratory wells were examined by standard laboratory tests and complemented with statistical analyses to quantitatively determine the main terrain attributes. Two main hydro-geological units were recognized, although a number of embedded layers defined amultilevel aquifer. Grain-size distribution derived from sieve analysis and the coefficient of uniformity showed that soils are poorly sorted. On the other hand, hydraulic conductivity was measured by anumber of parameters such as a log-normal distribution. Conductivity was also predicted by empirical formulas, yielding values up to three orders of magnitude higher. Discrepancies were explained interms of soil anisotropy and intrinsic differences in the calculation methods. Based on the Shepherd's approach, a power relationship between permeability and grain size was found at 2 wells. Hydraulicconductivity was also correlated to porosity. However, this  nterdependence was not systematic and therefore, properties at many parts of the profile were considered to be randomly distributed. Finally,logs of electrical conductivity suggested that variations of soil hydraulic properties can be associated to changes in water quality. In spite of the remaining uncertainties, results yielded from the study are useful to better understand the numerical modelling of the subsurface system in the site

Managing Groundwater Radioactive Contamination at the Daiichi Nuclear Plant

The Great East Japan Earthquake and tsunami of March 2011 severely damaged three reactors at the Fukushima Daiichi nuclear power station, leading to a major release of radiation into the environment. Groundwater flow through these crippled reactors continues to be one of the main causes of contamination and associated transport of radionuclides into the Pacific Ocean. In this context, a number of strategies are being implemented to manage radioactive pollution of the water resources at the nuclear plant site. Along with water treatment and purification, it is critical to restrict the groundwater flow to and from the reactors. Thus, the devised strategies combine walls containment, bores abstraction, infiltration control, and the use of tanks for the temporary storage of contaminated waters. While some of these techniques have been previously applied in other environments, they have never been tested at such a large scale. Therefore, their effectiveness remains to be seen. The present manuscript presents an overview of the methods being currently implemented to manage groundwater contamination and to mitigate the impact of hydrological pathways in the dispersion of radionuclides at Fukushima

The aftermath of the Fukushima nuclear accident: Measures to contain groundwater contamination

Several measures are being implemented to control groundwater contamination at the Fukushima Daiichi Nuclear Plant. This paper presents an overview of work undertaken to contain the spread of radionuclides, and to mitigate releases to the ocean via hydrological pathways. As a first response, contaminated water is being held in tanks while awaiting treatment. Limited storage capacity and the risk of leakage make the measure unsustainable in the long term. Thus, an impervious barrier has been combined with a drain system to minimize the discharge of groundwater offshore. Caesium in seawater at the plant port has largely dropped, although some elevated concentrations are occasionally recorded. Moreover, a dissimilar decline of the radioactivity in fish could indicate additional sources of radionuclides intake. An underground frozen shield is also being constructed around the reactors. This structure would reduce inflows to the reactors and limit the interaction between fresh and contaminated waters. Additional strategies include groundwater abstraction and paving of surfaces to lower water levels and further restrict the mobilisation of radionuclides. Technical difficulties and public distrust pose an unprecedented challenge to the site remediation. Nevertheless, the knowledge acquired during the initial work offers opportunities for better planning and more rigorous decisions in the future.Fil: Gallardo, Adrian Hugo. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Marui, Atsunao. Geological Survey of Japan; Japó

Managing Groundwater Radioactive Contamination at the Daiichi Nuclear Plant

The Great East Japan Earthquake and tsunami of March 2011 severely damagedthree reactors at the Fukushima Daiichi nuclear power station, leading to a major release of radiation into the environment. Groundwater flow through these crippled reactors continues to be one of the main causes of contamination and associated transport of radionuclides into the Pacific Ocean. In this context, a number of strategies are being implemented to manage radioactive pollution of the water resources at the nuclear plant site. Along with water treatment and purification, it is critical to restrict the groundwater flow to and from thereactors. Thus, the devised strategies combine walls containment, bores abstraction, infiltration control, and the use of tanks for the temporary storage of contaminated waters. While some of these techniques have been previously applied in other environments, they have never been tested at such a large scale. Therefore, their effectiveness remains to be seen. The present manuscript presents an overview of the methods being currentlyimplemented to manage groundwater contamination and to mitigate the impact ofhydrological pathways in the dispersion of radionuclides at Fukushima.Fil: Marui, Atsunao . Geological Survey of Japan; JapónFil: Gallardo, Adrian Hugo. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis; Argentin

Hydraulic characteristics of sedimentary deposits at the J-PARC proton-accelerator, Japan

Hydraulic characteristics of sediments were investigated at J-PARC for the purpose of site characterization in relation with the construction of Japan's largest proton-accelerator. A total of 340 samples extracted from 9 exploratory wells were examined by standard laboratory tests and complemented with statistical analyses to quantitatively determine the main terrain attributes. Two main hydro-geological units were recognized, although a number of embedded layers defined a<br />multilevel aquifer. Grain-size distribution derived from sieve analysis and the coefficient of uniformity showed that soils are poorly sorted. On the other hand, hydraulic conductivity was measured by a<br />number of parameters such as a log-normal distribution. Conductivity was also predicted by empirical formulas, yielding values up to three orders of magnitude higher. Discrepancies were explained in<br />terms of soil anisotropy and intrinsic differences in the calculation methods. Based on the Shepherd's approach, a power relationship between permeability and grain size was found at 2 wells. Hydraulic<br />conductivity was also correlated to porosity. However, this  nterdependence was not systematic and therefore, properties at many parts of the profile were considered to be randomly distributed. Finally,<br />logs of electrical conductivity suggested that variations of soil hydraulic properties can be associated to changes in water quality. In spite of the remaining uncertainties, results yielded from the study are useful to better understand the numerical modelling of the subsurface system in the site