최근 전기차 시장의 확장으로 배터리 산업이 급격히 성장함에 따라 폐배터리 리사이클링 기술 개발의 필요성이 증가하고 있다. 폐배터리 리사이클링 기술은 배터리 산업에 핵심적인 리튬, 코발트, 니켈 등 희소금속의 공급을 안정화하고 환경 및 인간의 건강에 미치는 영향을 경감할 수 있다. 본 총설에서는 금속 회수 기술의 배경이 되는 이론적 원리와 현재 상 용되고 있는 금속 회수 공정을 소개하고자 한다. 또한, 기존 공정의 문제점을 개선하려는 연구 및 기술 개발 동향을 서술하여 리사이클링 기술이 나아가야 할 방향을 소개하고자 한다.

The complexation of silicon with carbon materials is considered an effective method for using silicon as an anode material for lithium-ion batteries. In the present study, carbon frameworks with a 3D porous structure were fabricated using metal–organic frameworks (MOFs), which have been drawing significant attention as a promising material in a wide range of applications. Subsequently, the fabricated carbon frameworks were subjected to CVD to obtain silicon-carbon complexes. These siliconcarbon complexes with a 3D porous structure exhibited excellent rate capability because they provided sufficient paths for Li-ion diffusion while facilitating contact with the electrolyte. In addition, unoccupied space within the silicon complex, combined with the stable structure of the carbon framework, allowed the volume expansion of silicon and the resultant stress to be more effectively accommodated, thereby reducing electrode expansion. The major findings of the present study demonstrate the applicability of MOF-based carbon frameworks as a material for silicon complex anodes.

Semiconductor-based photocatalytic carbon dioxide ( CO2) reduction is of great scientific importance in the field of alleviating global warming and energy crisis. Surface amine modification and cocatalyst loading on the catalyst surface could improve CO2 adsorption capacity and photogenerated charge separation. Herein, amine-modified brookite–TiO2 ( NH2–B–TiO2) coupled metal species (Cu, Ag, Ni(OH)2) cocatalysts have been successfully synthesized by chemical reduction method. The photocatalytic CO2 reduction results show that the CH4 production rates of NH2– B–TiO2/Cu, NH2– B–TiO2/Ag, and NH2– B–TiO2/Ni(OH)2 are 3.2, 12.5, and 1.7 times that of NH2– B–TiO2 (0.74 μmmol g− 1 h− 1), respectively. Results show the introduction of metal species on the surface of the catalyst enhances the absorption range of sunlight and the photogenerated carrier separation efficiency, resulting in enhancing the performance of photocatalytic CO2 reduction. This work provides a strategy for designing metal species-loaded amine-modified brookite–TiO2 by surface/interface regulation to improve photocatalytic efficiency.

Mid-sized manufacturing companies, which account for 0.7%(5,480 companies), 13.8%(1.169 million persons) of total employment, and 15.7% of total sales, have recently experienced a lot of difficulties in management activities due to the impact of COVID-19, the U.S.-China trade war, and the collapse of global supply chains. To overcome this, revitalization of quality management activities to strengthen corporate competitiveness is emerging as an urgent task. In order for these quality management activities to achieve their intended purpose, the positive leadership of corporate managers is very important above all else. There have been many studies related to positive leadership, but most have focused on charismatic leadership and transformational leadership centered on large companies or small and medium-sized enterprises. Therefore, this study aims to present ways to strengthen the leadership of managers by empirically analyzing how the positive leadership of managers of mid-sized manufacturing companies, which was relatively under-researched, affects quality management activities and Business performance(Balanced Score Card; BSC).

인공 고관절 치환술에 사용되는 금속 삽입물은 크기와 성분에 따라 주변 조직과 크고 작은 자화율의 차이를 일으켜 다양한 금속 인공물의 원인이 되며, 영상에 진단적 가치를 떨어뜨린다. 수신대역폭을 높이는 것은 인공물 감소에 효과가 있으나, 높은 수신대역폭은 획득 영상의 신호대잡음비를 감소시키는 단점이 있어 일정 수치 이상으로는 적용 하기에는 어려움이 있다. 딥러닝 알고리즘은 영상의 신호대잡음비를 높이고 전체 영상에서 균일하게 배경 잡음을 제거하는 데 매우 효과적이다. 이에 본 연구에서는 금속 인공물 감소를 위해 기존에 높은 수신대역폭을 이용하는 MARS(metal artifact reduction sequence) 프로토콜과 더욱 높은 수신대역폭을 설정한 프로토콜(Ultra MARS) 을 획득한 후 딥러닝을 이용하여 딥러닝 Ultra MARS로 변환한 후에 금속 인공물의 차이를 비교하였다. 딥러닝 적 용 후 Ultra MARS에서 적용 전 또는 기존의 MARS 기법보다 인공물의 크기가 작게 측정이 되었다. 또한, 인공물의 전체적인 SSIM(structural similarity index measure)에서도 기존의 MARS 기법보다 전체면적이 작게 측정되었 다. 더 나아가 SSIM의 결과 딥러닝 적용 전후의 구조적 유사성 역시 유사하게 나왔다. 딥러닝 알고리즘을 기존에 인공물을 줄이기 위해 사용하는 MARS와 같은 기법에서도 월등하게 높은 수치를 사용하는 강조영상을 획득 가능하 며 영상의 인공물도 줄이며, 영상의 대조도 또한 유지되는 영상을 제공할 수 있을 것으로 사료된다.

β-Ga2O3 has become the focus of considerable attention as an ultra-wide bandgap semiconductor following the successful development of bulk single crystals using the melt growth method. Accordingly, homoepitaxy studies, where the interface between the substrate and the epilayer is not problematic, have become mainstream and many results have been published. However, because the cost of homo-substrates is high, research is still mainly at the laboratory level and has not yet been scaled up to commercialization. To overcome this problem, many researchers are trying to grow high quality Ga2O3 epilayers on hetero-substrates. We used diluted SiH4 gas to control the doping concentration during the heteroepitaxial growth of β-Ga2O3 on c-plane sapphire using metal organic chemical vapor deposition (MOCVD). Despite the high level of defect density inside the grown β-Ga2O3 epilayer due to the aggregation of random rotated domains, the carrier concentration could be controlled from 1 × 1019 to 1 × 1016 cm-3 by diluting the SiH4 gas concentration. This study indicates that β-Ga2O3 hetero-epitaxy has similar potential to homo-epitaxy and is expected to accelerate the commercialization of β-Ga2O3 applications with the advantage of low substrate cost.

Selenium (Se), a vital trace element found naturally, plays a pivotal role for human being in low concentrations. Notably, within the spectrum of essential elements, Se possesses the most restricted range between the dietary deficiency (< 40 μg day-1) and the acute toxicity (> 400 μg day-1). Therefore, it is of paramount importance to maintain bioavailable Se levels within permissible limits in our drinking water sources. Among the various Se species, inorganic variants such as selenite (SeO3 2-) and selenate (SeO4 2-) are highly water-soluble, with SeO3 2- being notably more toxic than SeO4 2-. Consequently, the primary focus lies in effectively sequestering SeO3 2- from aquatic environments. Numerous methods have been investigated for SeO3 2- adsorption, including the use of metal oxides and carbon-based materials. Especially, iron oxides have garnered extensive attention due to their water stability and environmentally friendly properties. Nevertheless, their limited surface area and insufficient adsorption sites impose constraints on their efficacy as materials for SeO3 2- removal. Recently, metal–organic frameworks (MOFs), composed of metal centers bridged by organic linkers have increasingly focused as promising adsorbents for SeO3 2- removal, offering significant advantages such as large surface areas, high porosities, and structural versatility. Furthermore, there is a growing interest in defective MOFs, where intentional defects are introduced into the MOF structure. This deliberate introduction of defects aims to enhance the adsorption capacity by increasing the number of available adsorption sites. In this context, herein, we present the Fe-BTC (BTC = 1,3,5-benzenetricarboxylic acid) synthesized via a post-synthetic metal-ion metathesis (PSMM) approach, which is one of the defect engineering methods applied to metal sites. We employ the well-established MOF, HKUST-1, known for its substantial surface area, as the pristine MOF. While the pristine MOF has a crystalline phase, during the PSMM process, Fe-BTC is transformed into an amorphous phase by allowing the introduction of numerous metal defect sites. These introduced metal defect sites serve as Lewis acidic sites, enhancing the adsorption capability for selenite. Furthermore, despite its amorphous nature, Fe-BTC exhibits a substantial surface area and porosity comparable to that of the crystalline pristine MOF. Consequently, Fe-BTC, distinguished by its numerous adsorption sites and its high porosity, demonstrates a remarkable capacity for selenite adsorption.

Owing to the rapid rise of global energy demands, the operation of nuclear power plants is still indispensable. However, following the nuclear accident at Fukushima-Daiichi in 2011, the secure sequestration of radioactive waste has become critical for ensuring safe operations. Among various forms of nuclear wastes, capturing radioactive organic iodide (ROIs, e.g., methyl iodide, ethyl iodide, and propyl iodide) as one of the important species in gas phase waste has been challenged owing to the insufficient sorbent materials. The environmental release of ROIs with high volatility can give rise to adverse effects, including the accumulation of these substances in the thyroid and the development of conditions such as hypothyroidism and thyroid cancer. Compared to an iodine molecule, ROIs exhibit low affinity for conventional sorbents such as Ag@mordenite zeolite and triethylenediamine-impregnated activated carbon (TED@AC), resulting in lower sorption rates and capacities. Furthermore, in conditions resembling practical adsorption environments with high humidity, the presence of H2O significantly impedes the adsorption process, leading to a nearly complete cessation of adsorption. To address these issues, metal-organic frameworks (MOFs) can be effective alternative sorbents owing to their high surface area and designable and tailorable pore properties. In addition, the wellfined crystalline structures of MOFs render in-depth study on the structure-properties relationship. However, there has been limited research on the adsorption of ROIs using MOFs, with the majority of adsorption processes relying on highly reversible physisorption. This type of ROIs adsorption not only exists in a precarious state that is susceptible to volatilization but also exhibits significantly reduced adsorption capabilities in humid environments. Thus, for the secure adsorption of the volatile ROIs, the development of sorbents capable of chemisorption is highly desirable. In this study, we focused on ROIs adsorption by electrophilic aromatic substitution with the electron-rich m-DOBDC4− (m-DOBDC4− = 4,6-dioxo-1,3-benzenedicarboxylate) present in Co2(m -DOBDC). The chemisorption of ROIs via electrophilic aromatic substitution not only leads to the formation of C-C bonds, ensuring stability but also triggers color changes in the crystal by interacting with open-metal sites and iodide ions. Leveraging these advantages, we developed an infrared radiation-based sensing method that demonstrates superior performance, exhibiting high adsorption capacities and rates, even under the challenging conditions of high-humidity practical environments.

This study explores the impact of metal doping on the surface structure of spent nuclear fuels (SNFs), particularly uranium dioxide (UO2). SNFs undergo significant microstructural changes during irradiation, affecting their physical and chemical properties. Certain elements, including actinides and lanthanides, can integrate into the UO2 lattice, leading to non-stoichiometry based on their oxidation state and environmental conditions. These modifications are closely linked to phenomena like corrosion and oxidation of UO2, making it essential to thoroughly characterize SNFs influenced by specific element doping for disposal or interim storage decisions. The research employs X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy to investigate the surface structure of UO2 samples doped with elements such as Nd3+, Gd3+, Zr4+, Th4+, and ε-particles (Mo, Ru, Pd). To manufacture these samples, UO2 powders are mixed and pelletized with the respective dopant oxide powders. The resulting pellet samples are sintered under specific conditions. The XRD analysis reveals that the lattice parameters of (U,Nd)O2, (U,Gd)O2, (U,Zr)O2, and (U,Th)O2 linearly vary with increasing doping levels, suggesting the formation of solid solutions. SEM images show that the grain size decreases with higher doping levels in (U,Gd)O2, (U,Nd)O2, and (U,Zr)O2, while the change is less pronounced in (U,Th)O2. Raman spectroscopy uncovers that U0.9Gd0.1O2-x and U0.9Nd0.1O2-x exhibit defect structures related to oxygen vacancies, induced by trivalent elements replacing U4+, distorting the UO2 lattice. In contrast, U0.9Zr0.1O2 shows no oxygen vacancy-related defects but features a distinct peak, likely indicating the formation of a ZrO8-type complex within the UO2 lattice. ε-Particle doped uranium dioxide shows minimal deviations in surface properties compared to pure UO2. This structural characterization of metal-doped and ε-particle-doped UO2 enhances our understanding of spent nuclear fuel behavior, with implications for the characterization of radioactive materials. This research provides valuable insights into how specific element doping affects the properties of SNFs, which is crucial for managing and disposing of these materials safely.

Noble metal phase, present in used fuel, are fission products that can be found as metallic precipitates in used nuclear fuel. They exist as small particles (nm~um) in grain boundaries of the used fuels. Since they are particles deposited between the grain structures, they can be considered as defects in the pellet structure. Thermal expansion of fuels with noble metal is slightly higher than that of bare fuels. The fuels at high temperature, such as immediately after being discharged from nuclear reactors, may be subject to fuel failure if sufficient cooling is not provided. Recent research has shown that the noble metals can migrate into the rim space between the pellet and the cladding, and be deposited in the inner layer of the claddings. therefore, the mechanical integrity of the cladding can be degraded by noble metals, as well as the pellets. The concentration of the noble metal phase should be considered to evaluate the effect of the noble metals on the fuel integrity, after discharge from the reactors. SCALE/ORIGEN code was used to evaluate the noble metals in fuel assembly-scale, and the radial distribution in the fuel assembly. The radial distribution of the reactor power was derived from the SCALE/TRITON, considering Westinghouse 17×17. Square cell model was chosen for the geometry and 1/4 model was applied to reduce the computation time.

Bisphenol-A, also known as BPA, is commonly used as a building block for epoxy and polycarbonate plastics. However, it has been recently identified as a major source of water pollution due to its release into the water from plastic products. BPA-based resins can also contaminate the water with high concentrations of BPA, which can enter the water bodies through production units and wastewater discharge. Photocatalysis, particularly the photo-Fenton process, is an effective method for wastewater treatment and degrading pollutants. Titanium dioxide (TiO2) is usually chosen based on its high photocatalytic properties and high performance. However, its wide band gap energy is a major issue for the photocatalytic process. This means that the catalyst can only exhibit high photocatalytic performance under UV-light irradiation and usually requires an acidic pH, which limits its use. In order to address the aforementioned issues, a visible-light photoactive photo-Fenton reaction has been successfully developed to degrade bisphenol A at natural pH using H2O2. The process was highly efficient, achieving complete degradation of phenol in just three hours of visible light irradiation with Cu-MOF. This environmentally friendly Fenton process has the advantage of occurring at natural pH levels with the presence of H2O2, providing a new perspective for efficient degradation. The photocatalyst was characterized using single X-ray diffraction (SC-XRD), powder X-ray diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR), and UV–vis diffuse reflectance spectroscopy (DRS).

As unit 1 of Kori was permanently shut down in June 2017, domestic nuclear industry has entered the path of decommissioning. The most important thing in decommissioning is cost reduction. And volume reduction of radioactive waste is especially important. According to the IAEA report, more than 4,000 tons of metallic waste is generated during the decommissioning of a 1,000 MWe reactor and most of these wastes are LLW or VLLW. To reduce amount of metallic waste dramatically, we should choose efficient decontamination method. In this study, we conducted dry ice and bead blasting decontamination. We prepared Inconel-600 and STS-304 specimen with dimensions of 30 mm × 30 mm × 5 mm. Loose and fixed contamination was applied on the surface of specimen using SIMCON method. Bead and dry-ice blasting was conducted by spraying alumina and dry ice pellet at the same pressure and distance for the same time. The removal of loose contamination was observed using microscope. It was found that contaminants are significantly removed using both dry ice blasting and bead blasting. However, some abrasive material remained on the surface of specimen. The removal of fixed contamination was verified by weight comparison before and after experiment and cobalt concentration comparison before and after experiment using X-ray Fluorescence Spectroscope (XRF). At least 90% of the cobalt was removed, but some abrasive particle was also remained on the surface of specimen. In this study, it is confirmed that the effectiveness of manufacturing a large-scale abrasive decontamination facility, and it is expected that this technology can be used to effectively reduce the amount of metallic waste generated during decommissioning.

The critical hazards generated from operation of a melting facility for metal radioactive waste are mainly assumed to be such as vapor explosion, ladle breakthrough and failure in the hot-cell or furnace chamber using remote equipment. In case of vapor explosion, material containing moisture and/or enclosed spaces may, due to rapid expansion of gases when heated, cause an explosion and/or violent boiling. The rapid expansion of gases may lead to ejection of molten radioactive metal from the furnace into the furnace hall. If there is a large amount of liquid the explosion may damage or destroy technical barriers such as facility walls. The consequences for the facility ranges from relatively mild to very severe depending on the force of the explosion as well as the type of waste being melted. Nonradiological consequences may be physical damage or destruction of equipment and facility barriers, such as walls. Due to the radiological consequences a longer operational shutdown would likely be required. Cleanup efforts would include cutting of solidified metal in a problematic radiological environment requiring use of remote technology before damage and repair requirements can be assessed. Even though there is a risk for direct physical harm to operators for example in the control room and hot-cell, this analysis focuses mainly on the radiological impact. The extent to which remote equipment could be used in the decontamination effort will largely determine the health consequences to the workers. It is reasonable to assume that there will be a need for workers to participate manually in the effort. Due to the potentially large dose rates and the physical environment, it is possible that the maximum allowable dose burden to a worker will be reached. No major consequence for the environment is expected as most of the radioactivity is bound to the material. In case of ladle breakthrough, a ladle breakthrough involves loss of containment of the melt due to damage of the ladle. This may be caused e.g. by increased wear due to overheating in the melt, or from physical factors such as mechanical stress and impact from the waste. A ladle breakthrough may lead to spread of molten metal in the furnace hall. Molten metal coming into contact with the surrounding cooling equipment may cause a steam explosion. The consequences of a ladle breakthrough will depend on the event sequence. The most severe is when the molten metal comes into contact with the cooling system causing a vapor explosion. The basic consequences are assumed to be similar to those of the vapor explosion above. While the ejection of molten metal is likely more local in the ladle breakthrough scenario, the consequences are judged to be similar. In case of failure in the hot-cell or furnace chamber using remote equipment, the loss of electric supply or technical failure in the furnace causes loss of power supply. If not remedied quickly, this could lead to that the melt solidifies. A melt that is solidified due to cooling after loss of power cannot be removed nor re-melted. This may occur especially fast if there is not melted material in the furnace. An unscheduled replacement of the refractory in the furnace would be required. It could be unknown to what degree remote equipment can be used to cut a solidified melt. It is therefore assumed that personnel may need to be employed. This event could not have any impact on environment

Various radioactive metal wastes are generated during operation and decommissioning of nuclear facilities. Radioactive metal wastes with complex geometries or volumetric contamination can be difficult to decontaminate and disposal costs may increase. To solve these problems, the radioactive metal wastes can be treated by melting method. In this study, we designed a melting furnace system of air induction melting type, which is widely utilized due to its advantages of good thermal efficiency, uniform heating and guaranteed safety for radioactive material. By utilizing the melting furnace system, volatile radionuclides existed in the base material can be captured in the form of gas or dust by the filter. The radionuclides whose chemical properties can easily form metal oxides present as slag. For this reason, the specific radioactivity of the base material can be reduced. Radionuclides that are difficult to transport to slag and dust are uniformly distributed in the base material. A dedicated power supply and a transformer were necessary to be included in the melting furnace system since the induction furnace uses high-frequency currents. In addition, a hood is placed on top of the furnace to capture fumes generated during melting, and additional hoods were installed around the furnace to remove airborne dust. In particular, a dust collection unit consisting of a cyclone and a HEPA filter were constructed to effectively collect dust containing radionuclides. During the melting process, the slag is removed and accumulated separately, and the ingot production system was designed to produce the ingot using molten metal. The furnace was constructed for tilting the molten metal by moving the furnace using hydraulic system. The water cooling system and cooling tower were prepared to cool off the equipment with high temperature during melting is cooled off. The above process was specified in the operating procedure developed for this melting furnace system, and the operator shall operate and inspect according to the prescribed procedures. The radioactivity concentration in the sample taken in the step of tilting shall be analyzed whether they meet clearance level for self-disposal determined and publicly announced by the Commission. We can conduct self-disposal for the product of melting furnace system confirmed by the Commission as having the radioactivity concentration by nuclide not exceeding the value determined by the Commission.

For the disposal of radioactive waste from nuclear facilities, assessing their radioactivity inventories is essential. As a result, countries with nuclear facilities are implementing assessment schemes tailored to their respective policies and available resources for radioactive waste management. This paper specifically describes the assessment scheme for radioactivity inventory applied to metal waste generated during the dismantling of the Japan Power Demonstration Reactor (JPDR), a 1.25 MW BWR. The distinctive aspect of the Japanese approach lies in the fact that, for a pair of a key nuclide and a difficult-to-measure (DTM) nuclide that lack a significant correlation in their concentrations, the mean activity concentration method was used. In this method, an arithmetic average of all measurements of the DTM nuclide from representative drums, including MDAs (Minimum Detectable Activities), was assigned to the concentration of the DTM nuclide for all drums, regardless of the concentration of its paired key nuclide. Conversely, for a specific pair of a key nuclide and a DTM nuclide with a significant correlation, the scaling factor method was applied, as is common in many other countries. This Japanese case can serve as a valuable reference for Korea, which does not have the option of using the mean activity concentration method in its assessment scheme.