• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1206-1212
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• 2022

Cold-crucible induction melting (CCIM) technology has been intensively studied as an advanced vitrification process for the immobilization of highly radioactive waste. This technology uses high-frequency induction to melt a glass matrix and waste, while the outer surface of the crucible is water-cooled, resulting in the formation of a frozen glass layer (skull). In this study, for the fabrication of borosilicate glass waste form, CCIM operation test with 60 kg of glass per batch was conducted using surrogate wastes composed of Cs, Sr, and Nd as a representative of highly radioactive nuclides generated during spent nuclear fuel management. A 60 kg-scale glass waste form was successfully fabricated through melting and draining processes using a CCIM system, and its physicochemical properties were analyzed. In particular, to enhance the controllability and reliability of the draining process, an air-cooling drain control method that can control draining through air-cooling near drain holes was developed, and its validity for draining control was verified. The method can offer controllability on various draining processes, such as molten salt or molten metal draining processes, and can be applied to a process requiring high throughput draining.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2418-2425
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• 2021

Monazite is a phosphate mineral that contains thorium (Th) and rare earth elements. The Th concentration in monazite can be as high as 500 ppm, and it has the potential to be used as fuel in the nuclear power system. Therefore, this study aimed to conduct the techno-economic analysis (TEA) of Th extraction in the form of thorium oxide (ThO₂) from monazite. Th can be extracted from monazite through an alkaline fusion method. The TEA of ThO₂ production studied parameters, including raw materials, equipment costs, total plant direct and indirect costs, and direct fixed capital cost. These parameters were calculated for the production of 0.5, 1, and 10 ton ThO₂ per batch. The TEA study revealed that the highest production cost was ascribed to installed equipment. Furthermore, the highest return on investment (ROI) of 21.92% was achieved for extraction of 1 ton/batch of ThO₂, with a payback time of 4.56 years. With further increase in ThO₂ production to 10 ton/batch, the ROI was decreased to 5.37%. This is mainly due to a significant increase in the total capital investment with increasing ThO₂ production scale. The minimum unit production cost was achieved for 1 ton ThO₂/batch equal to 335.79 $/Kg ThO₂.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.40-45
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• 2022

The electrical/thermal stabilities and magnetic field controllability of a no-insulation (NI) high-temperature superconducting magnet are characterized by contact resistance between turn-to-turn layers, and the contact resistance characteristics are determined by properties of conductor surface and winding tension. In order to accurately predict the electromagnetic characteristics of the NI coil in a design stage, it is necessary to control the contact resistance characteristics within the design target parameters. In this paper, the contact resistance and critical current characteristics of a rare-earth barium copper oxide (REBCO) conductor were measured to analyze the effects of surface treatment conditions (roughness and oxidation level) of the copper stabilizer layer in REBCO conductor. The test samples with different surface roughness and oxidation levels were fabricated and conductor surface analysis was performed using scanning electron microscope, alpha step surface profiler and energy dispersive X-ray spectroscopy. Moreover, the contact resistance and critical current characteristics of the samples were measured using the four-terminal method in a liquid nitrogen impregnated cooling environment. Compared with as-received REBCO conductor sample, the contact resistance values of the REBCO conductors, which were post-treated by the scratch and oxidation of the surface of the copper stabilizer layer, tended to increase, and the critical current values were decreased under certain roughness and oxidation conditions.

• The Journal of Engineering Geology
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• v.32 no.2
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• pp.295-310
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• 2022

The Weolaksan and Sokrisan granites yield high SiO₂ and alkali (Na₂O+K₂O) contents and low CaO and P₂O₅ contents. The Al saturation index is ≥1.3, which indicates that the granites are peraluminous. The mean U and Th contents are 8.3 and 39.3 ppm, respectively, higher than typical Mesozoic granites in South Korea and about twice the global mean for granitic rocks. The causes of such high radioelement contents are related to high degrees of fractionation and the crustal origin of the granites. U- and Thbearing radioactive minerals occur in the granites include zircon, thorite, monazite, xenotime, fergusonite and uraninite. The fact that the mean Th/U ratio of the granites (5.4) is similar to the global average crustal value suggests that the radioelement contents of granite were controlled by the crustal source material. Given the correlation of Zr, Y, and heavy rare earth elements for U and Th, radioelements are more likely hosted by xenotime than zircon and monazite.

• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.61-68
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• 1992

Structural, magnetic and magneto-optical(1.0~3.2eV) properties of rare earth (Ce, Pr, Eu), transition metal(Ni, Co), and Al substituted polycrystalline Ba ferrite films grown by rf sputtering have been investigated. TEM studies revealed that crystal grains in the films were reduced in size from several hundred nm to the order of 1 nm with the decrease of rf power density during sputtering. By substituting Al, square hysteresis loops have successfully been obtained. It has been found that Niions strongly enhances Faraday rotation of the films in the visible range. It has been confirmed that Co ions also strongly enhances Faraday rotation of the films in the near infrared. En- hancement in Faraday rotation by Ce, Pr, and Eu ions has not been observed. The origin of the enhancement in magnetic and magneto-optical properties of the films is discussed.

• Membrane Journal
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• v.32 no.1
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• pp.13-22
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• 2022

Ever increasing global energy demand gives rise to uncontrollable environmental pollution. Demand on fossil fuel and consequent carbon emission leads to global warming and climate change. Nuclear energy is an alternative source to generate clean energy but mining of nuclear fuel is associated with harmful chemicals. Mining of valuable minerals from sea water by membrane separation process is a cost effective along with environmental friendly process. Separation and adsorption based mining of valuable minerals from sea water are another efficient process. Recovery of actinides from rare earth elements are very challenging and expensive process. Pressure driven membrane separation process is economically more viable along with environmental process. In this review membrane separation process are based on polyether sulfone, polyamide, polyimide, polyamidoxine and hybrid membranes. In case of adsorption process, mainly amidoxime kind of adsorbent are discussed.

• Analytical Science and Technology
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• v.20 no.6
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• pp.468-473
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• 2007

The chemical composition distribution of the surface samples collected from the loess plateau in China were estimated. Major elements concentration distribution difference between 10 different sampling site were not found except sample 3. This sample had higher contents of Ca, Mg, LOI and lower contents of Si, Fe, P, Na, Ti. And also, minor element contents such as Ba, Cr, Nb, Pb, Rb, Zr, V were lower than other samples. UCC-normalized abundances of the most elements were within $0.5-1.5{\times}UCC$ and Cr showed enrichment aspect. Rare-earth element (REE) analysis results showed light REE enriched pattern compared to heavy REE with negative Eu anomaly in condrite-normalized REE pattern.

• Transactions of Materials Processing
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• v.31 no.3
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• pp.124-128
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• 2022

NdFeB magnets have been positioned as the core materials in advanced technologies such as MRI (magnetic resonance imaging), FA (factory automation system), robot, motors, and so on based on the highest magnetic properties. To effectively improve the refined microstructure, the plastic deformation has been known as the good alternatives by the recrystallization. However, it has been regarded as being impossible because of the few slip systems in the RE-Fe-B magnets at room temperature. The purpose of this study was to investigate the possibility of control of grain refinement and magnetic anisotropy of NdFeB alloy powder by the severe plastic deformation. The NdFeB magnet powder was fabricated by gas atomization process, and the powder was pre-compacted at high temperature. The pre-compacted billets were deformed by HPT (high pressure torsion), and then the deformed billets were observed microstructure and magnetic properties. After the HPT process at room temperature, the grain size decreased with increasing because of the melted Nd-rich phase, and the anisotropy of Nd₂Fe₁₄B phase was formed after the HPT process.

• Journal of the Korean Electrochemical Society
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• v.26 no.4
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• pp.64-70
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• 2023

Global warming is getting worse since a dramatic increase in greenhouse gas emissions recently. As a result, the necessity and implementation of carbon neutrality is required more urgently. To do this, among various new and renewable energies, attention in hydrogen arises. Hydrogen as a carbon-free power source is an abundant resource on Earth and is eco-friendly. Eventually, perfectly eco-friendly hydrogen can be obtained through electrolysis of water. However, the catalyst used in the oxygen evolution reaction is rare and expensive, and has a durability issue. Consequently, the development of a non-precious metal catalyst is necessary. In this review paper, we summarize and introduce Co- and Mo- based catalysts among recently announced oxygen evolution catalysts. This will help understand the design of catalyst to increase the activity and durability of non-precious metal catalysts.

• Journal of the Mineralogical Society of Korea
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• v.24 no.4
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• pp.265-278
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• 2011

Clayey ores of the Jeonnam province mainly consist of pyrophyllite (monoclinic), kaolinite (1T), and minor amounts of quartz, muscovite, and feldspars. Mineralogical studies revealed that two kinds of clay minerals were mainly produced from the volcanic sediments with similar ages and compositions. Kaolinite deposits sometimes contain neither diaspore nor corundum, but alunites are often found in the upper portions of the kaolin ore bodies. On the other hand, corundum and diaspore are commoner in the pyrophyllite deposits than the kaolin deposits. As ages of rock formations are becoming younger, amounts of pyrophyllite and kaolinite are rather radically decreased, and finally disappeared. But muscovite, quartz, and plagioclase feldspars are inclined to be preserved because of weak alteration. Most of clay ore bodies contain purple tuff beds on the uppermost portion, and silicified beds, tuff, and lapillistone are found in an ascending order in the most of clay quarries. Chemical analyses show that higher contents of $Al_2O_3$ might not necessarily be due to the argillization, since some tuffs contain higher $Al_2O_3$ contents originated from feldspars. $SiO_2$ contents are fairly higher in the silicified beds than in those of adjacent formations, which might have been introduced from the ore bodies. And $K_2O$ contents are obviously lower than those of $Na_2O$ and CaO in the ores and their vicinities. Ignition losses of some of clays represent much higher contents than those of the ordinary ones because of the sporadic presence of alunite, diaspore and corundum which are accompanied with lots of $SO_4$ and $Al_2O_3$ contents. REE (rare earth element) abundances of most of volcanics and clay ores show rather higher LREE (light rare earth elements) contents, and represent small to moderately negative Eu anomalies. Though most of ores ususally show milky white color, fine-grained and well bedded formations which could be easily discernible in the most of outcrop. But more distinct characteristics are desirable where rather massive ore bodies exist. Purple tuffs and silicified beds above the ore bodies would be useful as marker horizons/key beds since they have rather obvious lithology, extension and mineralogy than those of other adjacent formations.