• Journal of the Korea Institute of Building Construction
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• v.17 no.3
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• pp.253-260
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• 2017

As global warming became a worldwide issue, a significant effort has been made on the development of technology related to $CO_2$ capture and storage. Geologic sequestration of $CO_2$ is one of those technologies for safe disposal of $CO_2$. Geologic sequestration stores $CO_2$ in the form of supercritical fluid into the underground site surrounded by solid rock, and concrete is used for prevention of $CO_2$ leakage into the atmosphere. In such case, concrete may experience severe damage by attack of supercritical $CO_2$, and especially in contact with underground water, very aggressive form of carbonation can occur. In this work, to prevent such deterioration in concrete, calcium phosphates were added to the portland cement to produce hydroxyapatite, one of the most stable mineral in the world. Temperature rise, viscosity, set and stiffening, and strength development of cement paste incorporating three different types of calcium phosphates were investigated. According to the results, it was found that the addition of calcium phosphate increased apparent viscosity, but decreased maximum temperature rise and 28 day compressive strength. It was found that monocalcium phosphate was found to be inappropriate for portland cement based material. Applicability of dicalcium and tricalcium phosphates for portland cement needs to be evaluated with further investigation, including the long term compressive strength development.

• Tunnel and Underground Space
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• v.26 no.1
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• pp.12-23
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• 2016

For a successful accomplishment of Carbon Capture Sequestration (CCS) projects, appropriate injection conditions should be designed and optimized for site specific geological conditions. In this study, we evaluated the effect of injection conditions such as injection temperature and injection rate on the geomechanical stability of CCS system in terms of TOUGH-FLAC simulator, which is one of the well-known T-H-M coupled analysis methods. The stability of the storage system was assessed by a shear slip potential of the pre-existing fractures both in a reservoir and caprock, expressed by mobilized friction angle and Mohr stress circle. We demonstrated that no tensile fracturing was induced even in the cold CO2 injection, where the injected CO2 temperature is much lower than that of the reservoir and tensile thermal stress is generated, but shear slip of the fractures in the reservoir may occur. We also conducted a scenario analysis by varying injected CO2 volume per unit time, and found out that it was when the injection rate was decreasing in a step-wise that showed the least potential of a shear slip.

• Economic and Environmental Geology
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• v.44 no.2
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• pp.123-133
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• 2011

The lab scale experiments to investigate the geochemical reaction among supercritical $CO_2$-mineral-brine which occurs at $CO_2$ sequestration sites were performed. High pressurized cell system (l00 bar and $50^{\circ}C$) was designed to create supercritical $CO_2$ in the cell, simulating the sub-surface $CO_2$ storage site. From the high pressurized cell experiment, the surface changes of Ca-feldspar, amphibole (tremolite) and olivine, resulted from the supercritical $CO_2$-mineral-brine reaction, were observed and the dissolution of minerals into the brine was also investigated. The mineral slabs were polished and three locations on the surface were randomly selected for the image analysis of SPM and the surface roughness value (SRV) of those locations were calculated to quantify the change of mineral surface for 30 days. At a certain time interval, SPM images and SRVs of the same mineral surface were acquired. The secondary minerals precipitated on the mineral surfaces were also analyzed on SEM/EDS after the experiment. From the experiments, the average SRV of Ca-feldspar increased from 2.77 nm to 20.87 nm for 30 days, suggesting that the dissolution of Ca-feldspar occurs in active when the feldspars contact with supercritical $CO_2$ and brine. For the amphibole, the average SRV increased from 2.54 nm to 8.31 nm and for the olivine from 0.77 nm to 11.03 run. For the Ca-feldspar, $Ca^{2+}$, $Na^+$, $Fe^{2+}$, $Si^{4+}$, $K^+$ and $Mg^{2+}$ were dissolved in the highest order and $Si^{4+}$, $Ca^{2+}$, $Fe^{2+}$ and $Mg^{2+}$ for the amphibole. Fe (or Mg) - oxides were precipitated as the secondary minerals on the surfaces of amphibole and olivine after 30 days reaction. Results suggested that $Ca^{2+}$, $Fe^{2+}$ and $Mg^{2+}$ rich minerals would be significantly weathered when it contacts with the supercritical $CO_2$ and brine at $CO_2$ sequestration sites.

• The Journal of Engineering Geology
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• v.31 no.1
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• pp.19-30
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• 2021

This study evaluated the injection rate and the injection efficiency of the artificial recharge in the upper drought-prone watershed region, where the remaining water was used for injection, by using a numerical model to secure water during a drought. As a result of a numerical model under the condition of diverse injection rates per a well and hydraulic characteristics of the aquifer, the optimal injection rate per a well was estimated as 50.0 ㎥/day, and the injection efficiency was simulated as 33.2% to 81.2% of the total injection volume. As the injection time was shorter, the injection efficiency tented to increase non-linearly. As the injection rate increased, the residual storage in aquifer increased and available groundwater amount also increased, which could be advantageous for drought relief. For a more accurate assessment of injection efficiency, the model will be validated using the field injection data and optimum scenarios will enable the efficient operation of the artificial recharge system in the study area.

• Economic and Environmental Geology
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• v.45 no.6
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• pp.661-672
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• 2012

Lab scale experiments to investigate the dissolution reaction among supercritical $CO_2$-sandstone-groundwater by using sandstones from Gyeongsang basin were performed. High pressurized cell system (100 bar and $50^{\circ}C$) was designed to create supercritical $CO_2$ in the cell, simulating the sub-surface $CO_2$ storage site. The first-order dissolution coefficient ($k_d$) of the sandstone was calculated by measuring the change of the weight of thin section or the concentration of ions dissolved in groundwater at the reaction time intervals. For 30 days of the supercritical $CO_2$-sandstone-groundwater reaction, physical properties of sandstone cores in Gyeongsang basin were measured to investigate the effect of supercritical $CO_2$ on the sandstone. The weight change of sandstone cores was also measured to calculate the dissolution coefficient and the dissolution time of 1 g per unit area (1 $cm^2$) of each sandstone was quantitatively predicted. For the experiment using thin sections, mass of $Ca^{2+}$ and $Na^+$ dissolved in groundwater increased, suggesting that plagioclase and calcite of the sandstone would be significantly dissolved when it contacts with supercritical $CO_2$ and groundwater at $CO_2$ sequestration sites. 0.66% of the original thin sec-tion mass for the sandstone were dissolved after 30 days reaction. The average porosity for C sandstones was 8.183% and it increased to 8.789% after 30 days of the reaction. The average dry density, seismic velocity, and 1-D compression strength of sandstones decreased and these results were dependent on the porosity increase by the dissolution during the reaction. By using the first-order dissolution coefficient, the average time to dissolve 1 g of B and C sandstones per unit area (1 $cm^2$) was calculated as 1,532 years and 329 years, respectively. From results, it was investigated that the physical property change of sandstones at Gyeongsang basin would rapidly occur when the supercritical $CO_2$ was injected into $CO_2$ sequestration sites.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.3
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• pp.1-13
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• 2018

Recently, the frequency and intensity of drought have been increasing due to the sudden abnormal climate in Korea. The occurrence of agricultural drought has been steadily increasing from 5 times in the 1980s to 2000s in 20 years, 6 times in the 10 years from 2000 to 2010, and 4 times in the recent period from 2011 to 2015. Therefore, this study analyzed the effect of water shortage caused by drought by improving the function of agricultural reservoir. The target area analyzed the data such as "Comprehensive Information System for Rural Water" operated by Korea Rural Community Corporation. As a result, we selected the target area as Wanju - gun, Jeollabuk - do in consideration of the rate of water storage compared with the normal 25 years, the completion year of the facility, the area of coverage per reservoir site and the low capacity. As a result of evaluating the improvement effect of agricultural facilities, it was analyzed that the irrigation area increased by about 25.7% when the water level was increased by 1m and the irrigation area increased by about 51.3% when the water level was increased by 2m. The results of the drought impact assessment after improving the function of the agricultural facilities were analyzed that it was effective to improve the function after more than 4m depth.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.285-290
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• 2007

Electrical and electromagnetic methods were widely applied to survey of civil engineering, environment site assessments and maintenance of underground structures in Korea. Electro-physical properties measurements of soil and rock are necessary in order to quantitatively estimate the ground from these survey results. A few geotechnical researcher groups have been simplified measurement system of the electro-physical properties, which was intermittently operating by the necessity. Recent strong concern about $CO_2$ underground storage and development of gas hydrate projects have urged many advanced countries. The electro-physical properties estimation of the deep object stratum is very importance for basic information of these research. So, advanced countries have a high-end measurement system with high temperature(200 degrees) and pressure(300 MPa), also they have been a lot of experience and know-how on the electro-physical properties measurement.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.2
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• pp.105-115
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• 2012

Necessity of demonstration test to evaluate the structural integrity of a basket for accident conditions arose during license approval procedure for the WSPP's dry storage facility named MACSTOR/KN-400. A drop test facility for demonstration was constructed in KAERI site and demonstration tests for basket drop were conducted. As the upper welding region of a loaded basket was collided with a dropped basket during the drop test, the welding in this region was fractured and leakage happened after the drop test. The enhancement of basket design was needed since the existing basket design was not able to satisfy the performance requirement. The directions for design modification were determined and six enhanced designs were derived based on these directions. Structural analyses and specimen tests for each enhanced design were conducted. By evaluating structural analysis results and test results, one among six enhanced designs was decided as a final design for revision. The final design was the one to reduce the height of central post of a basket and to decrease the impact velocity with a dropped basket. Test basket models were fabricated with accordance with the final enhanced design. Additional demonstration test was performed for this test model and all the performance requirements were satisfied.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.260-260
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• 2013

Multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and technological applications in magnetic/ferroelectric data-storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3 $ is a typical multiferroic material with a room temperature magnetoelectric coupling in view of high magnetic-and ferroelectric-ordering temperatures (Neel temperature $T_N$~647 K and Curie temperature $T_C$~1,103 K). Rare-earth ion substitution at the Bi sties is very interesting, which induces suppressed volatility of Bi ion and improved ferroelectric properties. At the same time, Fe-site substitution with magnetic ions is also attracting, and the enhanced ferromagnetism was reported. In this study, $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$ (x=0, 0.05 and 0.1) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ or 24 h to produce $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$. The samples were immediately put into an oven, which was heated up to $800^{\circ}C$ nd sintered in air for 30 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies).

• Economic and Environmental Geology
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• v.49 no.5
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• pp.371-380
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• 2016

This study aims to identify the mineraloical and petrographical characteristics of caprock from drilling cores of Pohang basin as a potential $CO_2$ storage site. Experiments and modeling were conducted in order to investigate the geochemical and mineralogical caprock effects of carbon dioxide. A series of autoclave experiments were conducted to simulate the interaction in the $scCO_2$-caprock-brine using a high pressure and temperature cell at $50^{\circ}C$ and 100 bar. Geochemical and mineralogical alterations after 15 days of $scCO_2$-caprock-brine sample reactions were quantitatively examined by XRD, XRF, ICP-OES investigation. Results of mineralogical studies, together with petrographic data of caprock and data on the physicochemical parameters of brine were used for geochemical modeling. Modelling was carried out using the The Geochemist's Workbench 11.0.4 geochemical simulator. Results from XRD analysis for caprock sample showed that major compositional minerals are quartz, plagioclase, and K-feldspar, and muscovite, pyrite, siderite, calcite, kaolinite and montnorillonite were included on a small scale. Results from ICP-OES analysis for brine showed that concentration of $Ca^{2+}$, $Na^+$, $K^+$ and $Mg^{2+}$ increased due to dissolution of plagioclase, K-feldspar and muscovite. Results of modeling for the period of 100 years showed that the recrystallization of kaolinite, dawsonite and beidellite, at the expense of plagioclase and K-feldspar is characteristic. Volumes of newly precipitation minerals and minerals passing into brine were balanced, so the porosity remained nearly unchanged. Experimental and modeling results indicate the interaction between caprock and $scCO_2$ during geologic carbon sequestration can exert significant impacts in brine pH and solubility/stability of minerals.