• Journal of the Korean Geosynthetics Society
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• v.15 no.3
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• pp.49-55
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• 2016

Field measurement units and a system were constructed and installed in a waste-dump slope at the Imgi mine to investigate and analyze the variations in the unsaturated characteristics of the soil. The field instrumentation system was composed of a data acquisition system (DAS), a solar system, and measuring sensors. The rainfall, matric suction, and volumetric water contents were continuously measured from the units in the instrumented site. The variations in matric suction and volumetric water content were primarily affected by the rainfall intensity. At the surface of the slope, the largest increase and decrease in the changes in matric suction and volumetric water content were observed during the wetting and drying processes, respectively. Also, the matric suction and volumetric water content were 5-35 kPa and 0.12-0.24, respectively. However, the ground water level was not suddenly increased just after rainfall but gradually increased after 2 or 3 days later.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.190-198
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• 2008

In this stduy, the column experiments were carried out assuming the soil was contaminated by leakage of gasoline containing MTBE from USTs and pipes around gas stations. Then, characteristics of MTBE transport in the soil were investigated using CXTFIT program. The column experiments with different soil properties, moisture content, organic matter content and flow rate were carried out. Some parameters(D, R, $\beta$, $\omega$) used in two-site non-equilibrium adsorption model were obtained from measuring the MTBE concentration in injection-liquid and in effluent and using CXTFIT program. In addition, The characteristics of MTBE transport in the soil was found using BTCs and obtained parameters. Consequently, the advection decreased as the increase of the content of fine particle and organic, while the MTBE transport by advection was enhanced as increasing flow rate and moisture content.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.215-224
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• 2001

The concept that the electrical properties of subsurface material can be affected by the introduction of contaminants might be applicable fur developing the leakage detection system for petroleum hydrocarbons of underground storage tanks and leachate coming from landfill. Investigations were conducted with diesel, NaCl solution, and leachate by laboratory tests. Simulation test was performed leaking at a certain point in the field. The measured resistance was exponentially decreased as the water content of uncontaminated unsaturated sand was increased. The resistance of soil was increased by diesel but decreased by NaCl solution or leachate. The optimum electrode spacings were found for NaCl solution, leachate and diesel. Electrolytic solutions were better detected by wider spacing than non electrolytic solution.

• Economic and Environmental Geology
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• v.30 no.5
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• pp.433-442
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• 1997

A dual-permeability fractal model of fluid flow is proposed. The model simulates groundwater flow in fissured dual aquifer system composed of Aquifer 1 and Aquifer 2. For this model. groundwater flow originates only from Aquifer 1 on the pumping well. The model considers wellbore storage and skin effects at the pumping well and then shows exact drawdown at the early time of pumping. Type curves for different flow dimensions and for two cases are presented and analyzed. The case 1 represents the aquifer system which consists of Aquifer 1 with low permeability and high specific storage and Aquifer 2 with high permeability and low specific storage. The case 2 is inverse to the case 1. Dimensionless drawdown curves in Aquifer 1 and Aquifer 2 shows characteristic trend each other. Consequently, the model will be useful to analyze pumping test data of different draw down patterns on the pumping well and observation wells.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.4
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• pp.293-301
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• 2013

Borehole Disposal Concept (BDC) was initiated by the South African Nuclear Energy Corporation (NECSA) with the view to improve the radioactive waste management practices in Africa. At a time when geological disposal of radioactive waste is being considered, the need to protect ground water from possible radioactive contamination and the investigation of radionuclides migration through soil and rocks of zone of aeration into ground water has becomes very imperative. This is why the Borehole Disposal Concept (BDC) is being suggested to address the problem. The concept involves the conditioning and emplacement of disused sealed radioactive sources in an engineered facility of a relatively narrow diameter borehole (260 mm). Tanzania is operating a Radioactive Waste Management Facility where a number of spent sealed radioactive sources with long and short half lives are stored. The activity of spent sealed radioactive sources range from (1E-6 to 8.8E+3 Ci). However, the long term disposal solution is still a problem. This study therefore proposing the country to adopt the BDC, since the repository requires limited land area and has a low probability of human intrusion due to the small footprint of the borehole.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11a
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• pp.134-142
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• 2005

The experimental setups for flow visualization and processes identification in laboratory scale (so cal led Flow Lab.) has developed to get ideas and answer fundamental questions of flow and migration in geologic media. The setup was made of a granite block of $50{\times}50cm$ scale and a transparent acrylate plate. The tracers used in this experiments were tritiated water, anions, and sorbing cations as well as an organic dye, eosine, to visualize migration paths. The migration plumes were taken with a digital camera as a function of time and stored as digital images. A migration model was also developed to describe and identify the transport processes. Computer simulation was carried out not only for the hydraulic behavior such as distributions of pressure and flow vectors in the fracture but also for the migration plume and the elution curves.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.705-712
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• 2000

The fluid generally flows through fractures in crystalline rocks where most of underground storage facilities are constructed because of their low hydraulic conductivities. The fractured rock is better to be conceptualized with a discrete fracture concept, rather continuum approach. In the aspect of fluid flow in underground, the simultaneous flow of groundwater and gas should be considered in the cases of generation and leakage of gas in nuclear waste disposal facilities, air sparging process and soil vapor extraction for eliminating contaminants in soil or rock pore, and pneumatic fracturing for the improvement of permeability of rock mass. For the purpose of appropriate analysis of groundwater-gas flow, this study presents an unsteady-state multi-phase FEM fracture network simulator. Numerical simulation has been also conducted to investigate the hydraulic head distribution and air tightness around Ulsan LPG storage cavern. The recorded hydraulic head at the observation well Y was -5 to -10 m. From the results obtained by the developed model, it shows that the discrete fracture model yielded hydraulic head of -10 m, whereas great discrepancy with the field data was observed in the case of equivalent continuum modeling. The air tightness of individual fractures around cavern was examined according to two different operating pressures and as a result, only several numbers of fractures neighboring the cavern did not satisfy the criteria of air tightness at 882 kPa of cavern pressure. In the meantime, when operating pressure is 710.5 kPa, the most areas did not satisfy air tightness criteria. Finally, in the case of gas leaking from cavern to the surrounding rocks, the resulted hydraulic head and flowing pattern was changed and, therefore, gas was leaked out from the cavern ceiling and groundwater was flowed into the cavern through the walls.

• Tunnel and Underground Space
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• v.11 no.2
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• pp.132-145
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• 2001

The purpose and need of the study is to quantify the advantage or disadvantage of the environmental friendliness of the partitioning of nuclear fuel cycle. To this end, a preliminary study on the quantitative effect of the partition on the permanent disposal of spent PWR and CANDU fuel (HLW) was carried out. Before any analysis, the so-called reference radionuclide release scenario from a potential repository embedded into a crystalline rock was developed. Firstly, the feature, event and processes (FEPs) which lead to the release of nuclides from waste disposed of in a repository and the transport to and through the biosphere were identified. Based on the selected FEPs, the ‘Well Scenario’which might be the worst case scenario was set up. For the given scenario, annual individual doses to a local resident exposed to radioactive hazard were estimated and compared to that from direct disposal. Even though partitioning and transmutation could be an ideal solution to reduce the inventory which eventually decreases the release time as well as the peaks in the annual dose and also minimize the repository area through the proper handling of nuclides, it should overcome major disadvantages such as echnical issues on the partitioning and transmutation system, cost, and public acceptance, and environment friendly issues. In this regard, some relevant issues are also discussed to show the direction for further studies.

• Journal of Korea Soil Environment Society
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• v.2 no.3
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• pp.81-88
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• 1997

The purpose of this study is to assess contaminant transfer and environmental impacts to the surroundings by inadequate control of USTs. Several methodologies can be used in sampling procedure for the site assessment depending on the appearance of contaminants on the site and their types. In this case study because of site contaminants, randomized and/or triangle matrix techniques were used. As a result, the composition of materials in OO gas station were appeared in several status. From 1 to 2.5m depth, the soil was composed of silty sand and gravel, around 4m depth, weathered rock was appeared. Based on the preliminary and actual site investigation by DPT methodologies on the width and depth of the site with analysis of BTEX and TPH, no contamination was found in OO gas station, however, in one point because of careless dumping after refill by oil company, about 1731. 5 ppm of TPH appeared.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.439-448
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• 2001

A two-dimensional finite difference numerical model was developed in order to simulate two-phase fluid flow in a single fracture. In the model, variation of viscosity with pressure and that of relative permeability with water saturation can be treated. For the numerical solution, IMPES method was used, from which the pressure and the saturation of water and gas were computed one by one. Seven cases of model test using parallel plates for a single fracture were performed in order to obtain the characteristic equation of relative permeability which would be used in the numerical model. it was difficult to match the characteristic curves of relative permeability from the model tests with the existing emperical equations, consequently a logistic equation was proposed. As the equation is composed of the parameters involving aperture size, it can be applied to any fracture.