• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.187-196
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• 2005

Structural sites which cations can occupy in garnet structure are centers of the tetrahedron, octahedron, and distorted cube sharing edges with the tetrahedron and octahedron. Among them, the size of cation occuping at tetrahedral site (the center of tetrahedron) is closely related with the size of a unit cell of garnet. Accordingly, garnet containing iron with relative large ionic radii in tetrahedral site can be considered as a promising matrix for the immobilization of the elements with large ionic radii, such as actinides in radioactive wastes. We synthesized several garnets with the batch composition of $Ca_{1.5}GdCe_{0.5}ZrFeFe_3O_{12}$, and studied their properties and phase relations under various conditions. Mixed samples were fabricated in a pellet form under a pressure of $200{\~}400{\cal}kg/{\cal}cm^2$ and were sintered in the temperature range of $1100\~1400^{\circ}C$ in air and under oxygen atmospheres. Phase identification and chemical analysis of synthesized samples were conducted by XRD and SEM/EDS. In results, garnet was obtained as the main phase at $1300^{\circ}C$, an optimum condition in this system, even though some minor phases like perovskite and unknown phase were included. The compositions of garnet and perovskite synthesized from the batch composition of $Ca_{1.5}GdCe_{0.5}ZrFeFe_3O_{12}$ were ranged $[Ca_{l.2-1.8}Gd_{0.9-1.4}Ce_{0.3-0.5}]^{VIII}[Zr_{0.8-1.3}Fe_{0.7-1.2}]^{VI}[Fe_{2.9-3.1}]^{IV}O_{12}$ and $Ca_{0.1-0.5}Gd_{0.0-0.8}Ce_{0.1-0.5}\;Zr_{0.0-0.2}Fe_{0.9-1.1}O_3$, respectively. Ca content was exceeded and Ce content was depleted in the 8-coordinated site, comparing to the initial batch composition. This phenomena was closely related to the content of Zr and Fe in the 6-coordinated site.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.6 no.3
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• pp.171-178
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• 2008

Metal filter elements were newly introduced to the high temperature filter(HTF) system in the low- and intermediate-level radioactive waste vitrification plant. In order to evaluate the performance of various metal materials as filter media, elements made of AISI 316L, AISI 904L, and Inconel 600 were included to the test set of filter elements. At the visual inspection to the elements performed after completion of each test, a few dark spots were observed on the surface of some elements. Especially they were found much more at the AISI 316L elements than others. To check the dark spots are the corrosion phenomena or not, two kinds of analyses were performed to the tested filter elements. Firstly, the surfaces or the cross sections of filter specimens cut out from both normal area and dark spot area of elements were analyzed by SEM/EDS. The results showed that the dark spots were not evidences of corrosion but the deposition of sodium, sulfur and silica compounds volatilized from waste or molten glass. Secondly, the ring tensile strength were analyzed for the ring-shape filter specimens cut out from each kind of element. The result obtained from the strength tested showed no evidence of corrosion as well. Conclusionally, depending on the two kinds of analysis, no evidences of corrosion were found at the tested metal filter elements. But the dark spots formed on the surface could reduce the effective filtering area and increase the overall pressure drop of HTF system. Thus, continuous heating inside filter housing up to dew point will be required normally. And a few long-period test should be followed for the exact evaluation of corrosion of the metal filter elements.

• Economic and Environmental Geology
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• v.51 no.4
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• pp.323-343
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• 2018

This study defines the mineralogical, micro-textural and geochemical characteristics for the carbonate rocks and discusses the fluids that have affected the depositional environment of the Lower Makgol Formation in Seokgaejae section. Based on analysis of X-ray Diffraction (XRD), Scanning Electron Microscope-Energy Dispersive X-ray Spectrometry (SEM-EDS), Electron Probe Micro Analyzer-Wavelength Dispersive X-ray Spectrometry (EPMA-WDS) and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS), carbonate miorofacies in the basal and the lower members of the Makgol Formation are distinguished and classified into four types. Type 1 dolomite (xenotopic interlocking texture) and Type 2 dolomite (idiotopic interlocking texture) have relatively high Mg/Ca ratio, flat REE pattern, low Fe and Mn. Extensively interlocking textures in these dolomites indicate constant supply of Mg ion from hypersaline brine. Type 3 and Type 4 dolomite (scattered and loosely-aggregated texture) have relatively moderate Mg/Ca ratio, MREE enriched pattern, low to high Fe and Mn. These partial dolomitization indicate limited supply of Mg ion under the influx of meteoric water with seawater. Also, the evidence of Fe-bearing minerals, recrystallization and relatively high Fe and Mn in Type 4 indicates the influence of secondary diagenetic fluids under suboxic conditions. Integrating geochemical data with mineralogical and micro-textural evidence, the discrepancy between the basal and the lower members of the Makgol Formation indicates different sedimentary environment. It suggest that hypersaline brine have an influence on the basal member, while mixing meteoric water with seawater have an effect on the lower member of the Makgol Formation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.2
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• pp.183-193
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• 2018

Currently, the Korea Atomic Energy Research Institute (KAERI) is planning to build the Ki-Jang Research Reactor (KJRR) in Ki-Jang, Busan. It is important to safely dispose of low-level radioactive waste from the operation of the reactor. The most efficient way to treat radioactive waste is cement solidification. For a radioactive waste disposal facility, cement solidification is performed based on specific waste acceptance criteria such as compressive strength, free-standing water, immersion and leaching tests. Above all, the leaching test is important to final disposal. The leakage of radioactive waste such as $^{137}Cs$ causes not only regional problems but also serious global ones. The cement solidification method is simple, and cheaper than other solidification methods, but has a lower leaching resistance. Thus, this study was focused on the development of cement solidification for an enhancement of cesium leaching resistance. We used Zeolite and Loess to improve the cesium leaching resistance of KJRR cement solidification containing simulated KJRR liquid waste. Based on an SEM-EDS spectrum analysis, we confirmed that Zeolite and Loess successfully isolated KJRR cement solidification. A leaching test was carried out according to the ANS 16.1 test method. The ANS 16.1 test is performed to analyze cesium ion concentration in leachate of KJRR cement for 90 days. Thus, a leaching test was carried out using simulated KJRR liquid waste containing $3000mg{\cdot}L^{-1}$ of cesium for 90 days. KJRR cement solidification with Zeolite and Loess led to cesium leaching resistance values that were 27.90% and 21.08% higher than the control values. In addition, in several tests such as free-standing water, compressive strength, immersion, and leaching tests, all KJRR cement solidification met the waste acceptance or satisfied the waste acceptance criteria for final disposal.

• Journal of Conservation Science
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• v.26 no.2
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• pp.171-182
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• 2010

The slag excavated from Gyesil-ri in Gongju, Yeonje-ri in Cheongwon and Beopcheonsaji (temple) site in Wonju are analyzed by X-ray Fluorescence Analyzer, metallurgical microscope, SEM-EDS etc., for chemical composition and microstructure to figure out the raw material and the iron manufacturing technique. First of all, as a result of principal component analysis, the total Fe-content of slag from Gyesil-ri is 39 to 44% and the modified rate is 15 to 21%, which is common in ancient iron slag. Yeonje-ri site is found the ancient iron-smelting furnace. The total Fe-content of slag from Yeonje-ri is 41 to 43% and modified rate is 18~30%, which is also the general value in the ancient slag. However only slag is excavated in the residential area at Beopcheonsaji site and there is no iron making relic. In addition, the result of principal component analysis contains that the total Fe-content of Beopcheonsaji site is 52 to 57%, and modified rate is 8 to 14%. It shows that the total Fe-content of Beopcheonsaji site is higher than relic from Gyesil-ri and Yeonje-ri and the modified rate is lower than other sites. This results mean that recollecting rate of Fe in Beopcheonsaji site is lower than other sites. Also, as a result of minor elements analysis, the slag from Gyesil-ri has the higher level of Ti, V and Zr than other sites and the microstructure are observed as magnetite and ulvospinel, so that the raw material of slag is iron sand. But the slag from Yeonje-ri and Beopcheonsaji site are identified to use iron ore. As a result of microstructure observation, fayalite, gray-columnar crystal, is found in the slag from Yeonje-ri and big wustite as main phase is observed in the slag from Beopcheonsaji site. This study show that the slag from Yeonje-ri is made of smelt ash produced during smelting works and the slag from Beopcheonsaji site is made of forging ash produced during forging work concerning the excavated location and the microstructure.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.14-14
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• 2011

W (tungsten)-alloys will be the most promising plasma facing armor materials in highly loaded plasma interactive components of the next step fusion reactors due to its high melting point, high sputtering resistance and low deuterium/tritium retention. The bonding technology of tungsten to Cu alloy was one of the key issues. In this paper, W/CuCrZr diffusion bonding has been performed successfully by inserting pure metal interlay. The joint microstructure, interfacial elements migration and phase composition were analyzed by SEM, EDS, XRD, and the joint shear strength and micro-hardness were investigated. The mock-ups were fabricated successfully with diffusion bonding and the cladding technology respectively, and the high heat flux test and thermal fatigue test were carried out under actively cooling condition. When Ni foil was used for the bonding of tungsten to CuCrZr, two reaction layers, Ni4W and Ni(W) layer, appeared between the tungsten and Ni interlayer with the optimized condition. Even though Ni4W is hard and brittle, and the strength of the joint was oppositely increased (217 MPa) due primarily to extremely small thicknesses (2~3 ${\mu}m$). When Ti foil was selected as the interlayer, the Ti foil diffused quickly with Cu and was transformed into liquid phase at $1,000^{\circ}C$. Almost all of the liquid was extruded out of the interface zone under bonding pressure, and an extremely thin residual layer (1~2 ${\mu}m$) of the liquid phase was retained between the tungsten and CuCrZr, which shear strength exceeded 160 MPa. When Ni/Ti/Ni multiple interlayers were used for bonding of tungsten to CuCrZr, a large number of intermetallic compound ($Ni_4W/NiTi_2/NiTi/Ni_3T$) were formed for the interdiffusion among W, Ni and Ti. Therefore, the shear strength of the joint was low and just about 85 MPa. The residual stresses in the clad samples with flat, arc, rectangle and trapezoid interface were estimated by Finite Element Analysis. The simulation results show that the flat clad sample was subjected maximum residual stress at the edge of the interface, which could be cracked at the edge and propagated along the interface. As for the rectangle and trapezoid interface, the residual stresses of the interface were lower than that of the flat interface, and the interface of the arc clad sample have lowest residual stress and all of the residual stress with arc interface were divided into different grooved zones, so the probabilities of cracking and propagation were lower than other interfaces. The residual stresses of the mock-ups under high heat flux of 10 $MW/m^2$ were estimated by Finite Element Analysis. The tungsten of the flat interfaces was subjected to tensile stresses (positive $S_x$), and the CuCrZr was subjected to compressive stresses (negative $S_x$). If the interface have a little microcrack, the tungsten of joint was more liable to propagate than the CuCrZr due to the brittle of the tungsten. However, when the flat interface was substituted by arc interfaces, the periodical residual stresses in the joining region were either released or formed a stress field prohibiting the growth or nucleation of the interfacial cracks. Thermal fatigue tests were performed on the mock-ups of flat and arc interface under the heat flux of 10 $MW/m^2$ with the cooling water velocity of 10 m/s. After thermal cycle experiments, a large number of microcracks appeared at the tungsten substrate due to large radial tensile stress on the flat mock-up. The defects would largely affect the heat transfer capability and the structure reliability of the mock-up. As for the arc mock-up, even though some microcracks were found at the interface of the regions, all microcracks with arc interface were divided into different arc-grooved zones, so the propagation of microcracks is difficult.

• Journal of Preventive Medicine and Public Health
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• v.30 no.1 s.56
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• pp.77-101
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• 1997

In September 1994, residents of Gozan-dong, Incheon City, made a petition to the government about their health problems which might be caused by previous glass fibre landfill nearby 'H' company. In february 1995, at regular academic meeting of occupational and environmental medicine, a research team of 'D' University presented that they had found glass fibres in groundwater of the area through their survey. They were suspicious of probable association between ingestion of groundwater contaminated with glass fibres and skin tumors among residents. A joint research team was formed and carried out the survey of environment concerning groundwater and its glass fibre existence, and health assessment of residents in the area and industrial workers of 'H' company during May to November, 1995. Analysis of groundwater flow system indicates that the flow lines from the glass fibre landfill pass through or terminate at the 6 houses around the landfill. This means that the groundwater of the 6 houses around the glass fibre landfill could be affected by some possible contaminants from the landfill, but the groundwater quality of the other houses was irrelevant to the landfill. The qualitative and qualitative analyses for glass fibres in 54 groundwater samples including those from the nearby 6 houses, were carried out using SEM equipped with EDS, resulting in no evidence for the presence of glass fibres in the waters. Major precipitates, formed in waters while boiling, were identified as calcium carbonates, in particulary, aragonites in needle form. The results of health assessments of 889 residents in Gozan-dong, participated in this study, showed statistically significant differences in past medical histories of skin tumor and respiratory disease between the exposed group (31 persons who inhabited in 6 houses around the landfill) and the control group, but no significant differences in past medical histories of other diseases, such as cancer mortality, current gastroscopic findings, current skin diseases and respiratory diseases, etc. Also, we could not prove any glass fibres in excised specimens of 9 skin tumors in both groups and there were no health problems possibly associated with glass fibres in employees of the 'H' company. After all, we could not authenticate the association, raised by prior investigators, between groundwater streams, assumedly contaminated with glass fibres or not, and specific disease morbidities or common disease/symptom prevalences. That is, we could not find any glass fibres in groundwater as the only exposure factor of this study hypothesis, and there were not enough certain evidences such as increasing disease prevalences, for examples, skin, respiratory and gastrointestinal diseases etc, possibly related to glass fibre exposure, in exposed group. As a matter of course, the conditions for confirming causal association, for example, strength of the association, consistency of the association, specificity of the association, temporality of the association and dose-response relationship etc, have not been satisfied. In conclusion, we were not able to certify the hypothesis that contamination of groundwater with glass fibres might cause any hazardous health effects in residents who used it for drinking.

• Development and Reproduction
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• v.15 no.2
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• pp.87-98
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• 2011

The present experiment was performed to evaluate the osteogenic differentiation of human adipose tissue derived mesenchymal stem cells (ATMSCs) seeded in bioceramic-poly D,L-latic-co-glycolic acid (PLGA) scaffold. Osteogenic differentiation of ATMSCs were induced using the osteogenic induction (OI) medium. ATMSCs were cultured with OI medium during 28 days in well plate. The proliferation of ATMSCs in OI medium group was significantly increased for 14 days of plate culture but slowed after 21 days. On the other hand, proliferation in the control group showed constant increase for 28 days of culturing. The alkaline phosphatase (ALP) activity of ATMSCs in OI medium group increased during the 21 days of culture but decreased on 28 days. However, in control group ALP activity of ATMSCs was continuously decreased as time goes. Nodule was observed at 21 days of culture in OI medium group and confirmed accumulation of calcium in cell by alizarin red staining. ATMSCs were seeded in PLGA scaffold or in Bioceramic-PLGA scaffold, and cultured with OI medium. ALP activity of ATMSCs by osteoblast differentiation in each scaffold increased on 21 days of culture and decreased rapidly on 28 days. ALP activity of ATMSCs was increased highly in Bioceramic-PLGA scaffold compared to PLGA scaffold on 21 days of culturing. SEM-EDS analysis demonstrated that calcium and phosphate content and Ca/P ratio in Bioceramic-PLGA scaffold increased higher than in PLGA scaffold. Biodegradability of scaffold at 56 days after implantation showed that Bioceramic-PLGA scaffold was more biodegradable than PLGA scaffold. The results demonstrated that the differentiation of ATMSCs to osteoblast were more effective in scaffold culture than well plate culture. Bioceramic increased cell adhesion rate on scaffold and ALP activity by osteoblast differentiation. Also, bioceramic was considered to increase the calcium and phosphate in scaffold when ATMSCs was mineralized by osteogenic differentiation. Bioceramic-PLGA scaffold enhanced the osteogenesis of seeded ATMSCs compared to PLGA scaffold.

• Journal of the Mineralogical Society of Korea
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• v.22 no.3
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• pp.241-248
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• 2009

Kaolinite was synthesized from amorphous $SiO_2$ and $Al(OH)_3{\cdot}xH_{2}O$ as starting materials by hydrothermal reaction conducted at $250^{\circ}C$ and $30\;kg/cm^2$. The acidity of the solution was adjusted at pH 2. The synthesized kaolinite was characterized by XRD, IR, NMR, FE-SEM, TEM and EDS to clarify the formational process according to the reaction time from 2 to 36 hours. X-ray diffraction patterns showed after 2 h of reaction time, the starting material amorphous $Al(OH)_3{\cdot}xH_{2}O$ transformed to boehmite (AlOOH) and after the reaction time 5 h, the peaks of boehmite were observed to be absent thereby indicating the crystal structure is partially destructed. Kaolinite formation was identified in the product obtained after 10 h of reaction and the peak intensity of kaolinite increased further with reaction time. The results of TGA and DTA revealed that the principal feature of kaolinite trace are well resolved. TGA results showed 13 wt% amount of weight loss and DTA analysis showed that exothermic peak of boehmite observed at $258^{\circ}C$ was decreased gradually and after 10 h of reaction time, it was disappeared. After 5 h of the reaction time, the exothermicpeak of transformation to spinel phase was observed and the peak intensiy increased with reaction time. The results of FT-IR suggested a highly ordered kaolinite was obtained after 36 hours of reaction. It was identified by the characteristic hydroxide group bands positioned at 3,696, 3670, 3653 and $3620\;cm^{-1}$. The development of the hydroxyl stretching between 3696 and $3620\;cm^{-1}$, depends on the degree of order and crystalline perfection. TEM results showed that after 15 h reaction time, curved platy kaolinite was observed as growing of (001) plane and after 36 h, the morphology of synthetic kaolinite exhibited platy crystal with partial polygonal outlines.