• The Journal of Engineering Geology
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• v.15 no.3
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• pp.281-288
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• 2005

To evaluate a property of moisture distribution and volumetric water content on bentonite media the responses of complex dielectric constant were used which are measured by Frequency Domain Reflectometry with Vector Network Analyzer (FDR-V) system. The bentonite is widely used a barrier liner system in the waste disposal site, recently. In case of barrier liner system, generally, the coefficient of permeability should have to less than 10-7cm/sec. According to the results, the complex dielectric constants are increasing with increase the volumetric water content and temperature together. Also the variation of complex dielectric constant due to temperature gradient is confirmed that the moisture movements are increasing with the variations of temperature from high range to low range, which is represented the property of moisture distribution in the bentonite.

• Journal of the Korean Geotechnical Society
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• v.37 no.10
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• pp.5-11
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• 2021

The compacted bentonite buffer is one of the most important components in an engineered barrier system (EBS) to dispose of high-level radioactive waste (HLW) produced by nuclear power generation. The compacted bentonite buffer has a crucial role in protecting the disposal canister against the external impact and penetration of groundwater, so it has to satisfy the thermal-hydraulic-mechanical requirements. Even though there have been various researches on the investigation of thermal-hydraulic properties, few studies have been conducted to evaluate mechanical properties for the compacted bentonite buffer. For this reason, this paper conducted a series of unconfined compression tests and obtained mechanical properties such as unconfined compressive strength, elastic modulus, and void ratio of Korean compacted bentonite specimens with different water content and dry density values. The unconfined compressive strength and elastic modulus increased, and the Poisson's ratio decreased a little with increasing dry density. It showed that unconfined compressive strength and elastic modulus were proportional to dry density. However, there was not a remarkable correlation between mechanical properties and water content.

• Journal of the Mineralogical Society of Korea
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• v.17 no.3
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• pp.245-265
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• 2004

This study was to compare the geological occurrences and geneses of the Myogi, Tsukinuno, Dobuyama and Kawasaki bentonite deposits distributed in the Tertiary sedimentary basins of NE Japan, and to compare the mineralogical and physicochemical properties of their bentonites. The Japanese bentonite deposits are mainly distributed in the Green-tuff region which was formed in Neogene. The shape of ore body of the Myogi, Tsukinuno and Kawasaki deposits formed by the diagenesis are layered and stratiform. In contrast to this, the Dobuyama deposit formed by hydrothermal alteration shows the cone shape. The mineralization age of four deposits are 1.8 ～ 21 Ha from Early Miocene to Pliocene. The Dobuyama bentonite with the highest montmorillonite content shows the highest surface area, CEC, MB adsorption, and strengths. The Tsukinuno bentonite with a little high montmorillonite content is characterized by strong alkalinity, high viscosity and swelling. The Kawasaki bentonite, the Na-Ca mixed type, shows higher viscosity and swelling than the Ca-type Dobuyama bentonite. The Myogi bentonite with the lowest montmorillonite content shows the properties of low viscosity, In adsorption, strengths and a little high CEC and surface area. The high CEC and surface area of this deposit is due to the sufficient occurrence of zeolite. A strong dispersion in the Na-type bentonite and a strong flocculation in the Ca-type bentonite took place, and both the types show a slow flocculation with time. The physicochemical properties of the bentonite are mainly controlled by the montmorillonite content, interlayer cations, and impurity minerals such as zeolite. But bentonites inconsistent to this factors are sometimes occurred. This is maybe due to the crystal chemistry such as layer charge of montmorillonite and crystal morphology of montmorillonite such as aspect ratio.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.7 no.2
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• pp.101-107
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• 2009

Investigation of resaturation and thermal-hydro-mechanical behavior for the buffer of a repository requires measuring the water content of compacted bentonite. This study investigated the relative humidity of compacted bentonites using a humidity sensor (Vaisala HMT 334) applicable under high temperature and pressure, and then conducted a multi-regression analysis based on the measured results to determine relationships among the water content, relative humidity, and temperature. The relationships for the compacted bentonites with the dry densities of 1,500 $kg/m^3$ and 1,600 $kg/m^3$ were expressed as ${\omega}=0.196RH-0.029T+1.391({r^2=0.96)}$ and ${\omega}=0.199RH-0.029T+2.596({r^2=0.98)}$, respectively. These were then used to interpret the resaturation of bentonite blocks in the KENTEX test.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.777-782
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• 2013

In order to further reduce the sulfur content in liquid hydrocarbon fuels, a desulfurization process by adsorption for removing dimethyl sulfide (DMS) and propylmercaptan (PM) was investigated. Bentonite adsorbents modified by $CuCl_2$ for the desulfurization of model oil was investigated. The results indicated that the modified bentonite adsorbents were effective for adsorption of DMS and PM. The bentonite adsorbents were characterized by X-ray diffraction (XRD) and thermal analysis (TGA). The acidity was measured by FT-IR spectroscopy. Several factors that influence the desulfurization capability, including loading and calcination temperature, were studied. The maximum sulfur adsorption capacity was obtained at a Cu(II) loading of 15 wt %, and the optimum calcination temperature was $150^{\circ}C$. Spectral shifts of the ${\nu}$(C-S) and ${\nu}$(Cu-S) vibrations of the complex compound obtained by the reaction of $CuCl_2$ and DMS were measured with the Raman spectrum. On the basis of complex adsorption reaction and hybrid orbital theory, the adsorption on modified bentonite occurred via multilayer intermolecular forces and S-M (${\sigma}$) bonds.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.6 no.2
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• pp.101-109
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• 2008

For the Kyungju bentonite which is considered as a candidate material for the buffer and backfill in the high-level waste repository, the thermal conductivities of compacted bentonite and a bentonite-sand mixture were measured. The thermal conductivities of the compacted bentonites with a dry density of 1.2 to $1.8\;Mg/m^3$ and the bentonite-sand mixture with a dry density of 1.6 and $1.8\;Mg/m^3$ were measured within the gravimetric water content range of 10wt% to 20wt% and the sand fraction range of 10 to 30wt%. The thermal conductivity of compacted bentonite and a bentonite-sand mixture increases with increasing dry density and sand weight fraction in the case of constant water weight fraction, and increases with increasing water weight fraction and sand weight fraction in the case of constant dry density. The empirical correlations to describe the thermal conductivity of compacted bentonite and a bentonite-sand mixture as a function of water fraction at each dry density were suggested. These correlations can predict the thermal conductivities of bentonite and a bentonite-sand mixture with a difference below 10%.

• Korean Journal of Environmental Agriculture
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• v.11 no.2
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• pp.155-162
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• 1992

In order to extend the releasing period of granular formulation to approximately 20 days, the KC-6620-adsorbed granules were formulated with carriers and polyethylene glycol as adjuvant. The releasing rates of active ingredient from the formulations were evaluated in aqueous medium. The baked bentonite was found most effective carrier to sustain the release of KC-6620. Due to, however, low releasing rate of active ingredient after 20 days, bentonite formulation appeared to be of no practical for the short-term sustained release of KC-6620. The increased pore volume of bentonite granular formulation by adding pyrophyllite increased remarkably the released amount of KC-6620 from bentonite-pyrophyllite(4 : 6) granule up to 85% of total active ingredient incorporated. Addition of polyethylene glycol to the bentonite-pyrophyllite granule further increased the releasing rate of KC-6620. With KC-6620 content in the bentonite-pyrophyllite(4 : 6) granule, the releasing rate of active ingredient was markedly reduced.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.14 no.2
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• pp.135-147
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• 2016

The buffer in geological disposal system is one of the major elements to restrain the release of radionuclide and to protect the container from the inflow of groundwater. The buffer material requires long-term stability, low hydraulic conductivity, low organic content, high retardation of radionuclide, high swelling pressure, and high thermal conductivity. These requirements could be determined by the quantitative analysis results. In case of South Korea, the bentonites produced in Gyeongju area have been regarded as candidate buffer/backfill materials at KAERI (Korea Atomic Energy Research Institute) since 1997. According to the study on several physical and chemical characteristics of domestic bentonite in the same district, this is the Ca-type bentonite with about 65% of montmorillonite content. Through this study, we present the criteria for the performance evaluation items and methods when collecting new buffer/backfill materials.

• The Journal of Engineering Geology
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• v.9 no.2
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• pp.89-100
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• 1999

This study was carried out to assess the physicochemical properties of domestic bentonites and zeolites from Tertiary Formation as the candidate material for a engineered barrier of a radioactive waste repository. Natural bentonite and zeolite samples were collected from nine bentonite mines and six zeolite mines in Yeonil-Gampo area. The commercial products of bentonite and zeolite were obtained from local companies. The collected samples were investigated to study the following physicochemical properties: X-ray diffraction patterns, swelling, cation exchange capacity(CEC), specific surface area, montmorillonite content, pH, organic carbon content, thermal property, microstruciure and chemical composition. Based on the physicochemical properties of bentonite and zeolite, the bentonites from U-41 and G-46 mines and the zeolites from Daedo and Y-1 mines are regarded as the most desirable candidate materials.

• Geotechnical Engineering
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• v.8 no.3
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• pp.51-60
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• 1992

This paper represents the physical and engineering characteristics of admixed liners obtained from several laboratory tests. Fly ash and weathered granitic soil are selected as primary materials, and bentonite and cement are used as additives. The results show that the maximum dry density reaches peak values at 5% and 25% of bentonite for Seochon and Samchonpo fly ash respectively, and for the weathered granitic soil, the maximum dry density increases continuously as the amount of bentonite increases. The strength of the admixed materials is not sensitive to the bentonite content, although it increases when the additives is cement. The required amount of bentonite to reach the hydraulic conductivity less than 10-7cm/sec are 18, 30, 10% of the sample weights for Seochon and Samchonpo fly ashes and the weathered granitic soil. The amount of additives show significant differences and depend on the grain size and their distributions and the amount of fine content in the primary materials