본 연구는 소나무재선충병 방제대상지 선정의 효율성을 높이기 위해 진주시를 대상으로 소나무재선충병 잠재분포를 예측하였다. 예측에 사용된 MaxEnt 모델은 회귀분석을 기반으로 종 발생 확률 평가 및 다양한 잠재분포 예측에 이용되고 있다. 종속변수로는 소나무재선충병 감염목 자료를 사용하였으며, 독립변수로는 지리 ‧ 지형 ‧ 기후적 요인으로 총 15개 인자를 사용하였다. 잠재분포 예측 결과, 모델의 성능은 AUC가 0.801로 우수한 수준의 정확도를 나타냈다. 독립변수 중에는 전년도 감염목과의 거리, 6월 하순 강우량, 5월 강우량, 화목보일러와의 거리 순으로 잠재분포에 영향을 미치는 것으로 나타났다. 이러한 결과는 지속적인 소나무재선충병 감염목 DB 구축과 지리적 요인들에 대한 모니터링의 중요성이 크다는 것을 의미한다.

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.

Most of the C-14 produced is in the organic form, generated as methane (14CH4), methanol (14CH3OH), formaldehyde (14CH2O), and formic acid (14CO2H2). When analyzing C-14, it is transformed into the form of 14CO2, and its concentration is determined using LSC. Typical examples include the wet oxidation method, the combustion or Pyrolysis. The wet oxidation method uses strong acids and involves repeated operations, which generates large amounts of acid waste and secondary radioactive waste. The combustion method uses high temperatures, which requires an oxygen device. Pyrolysis also requires high temperature in a vacuum and catalysts. Catalysts are expensive because they are platinum-based. To compensate for these shortcomings, a C-14 analysis method using UV irradiation was developed. In this study, 100 mL of distilled water mixed with formic acid (CO2H2), potassium persulfate (K2S2O8), and silver nitrate (AgNO3) was irradiated with a 320-390 nm UV lamp to conduct a CO2 production reaction experiment. The UV range was measured using a photometer (UV Power puck II). The beaker was made of quartz in 150 mL size with three inlets : a temperature measurement, a sample inlet, and a collection tube connector. We changed the UV lamp used from a 450 W halogen lamp to a 100 W LED, which has a lower temperature and is safer. As a result of the experiment, CO2 bubbles were generated in the collection tube, due to the UV irradiation react, which uses oxidizer and catalysts. The maximum temperature of the solution irradiated with the LED UV lamp was less than 56°C. It confirmed the rate of bubble generation changed depending on the lamp distance, the amount of sample, oxidizer, and catalyst. In an experiment to confirm the reaction caused by heat, it was found that although a reaction occurred due to heat, the reaction was significantly lower than when using a UV lamp. The reproducibility experiment was conducted three times in total under the same conditions. It showed the same pattern. In the future, we plan to select mock samples, collect 14CO2 in Carbo- Sorb, and analyze them using LSC. The results of this research will be used as a technology to recover C-14 more safely and efficiently and will also be used to expand its application to the treatment of other wastes such as waste liquid and waste resin through simulated samples.

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).

Confirmation of the thermal behavior of spent fuel is one of the important points in the management of high-level radioactive waste. This is because various fission products exist in spent nuclear fuel, and a management plan according to their behavior is required. Among the fission products, epsilon particles exist in the form of metal deposits and have a great influence on their physical and chemical properties. However, observing the thermal behavior of epsilon particles is important for understanding spent fuel behavior in thermally environment, but it is difficult to maintain a consistent thermal environment. In this work, we report the thermal behaviors study of uranium oxide with epsilon particle using in situ high temperature X-ray diffraction. We measured the variation of temperature on the size of crystalline, which is a cell parameter in the reaction process. And then, the change of lattice parameters is calculated by Rietveld refinement.

The removal of aqueous pollutants, including dye molecules from wastewater remains one of the pressing problems in the world. Because of chemical stability and conjugated structure, dye molecules cannot be easy decomposed by heat with oxidizing reagents such as H2O2 and light. The most common representative of widespread organic pollutant is methylene blue (MB) with molecular formula C16H18ClN3S, which is important colorant and used in various chemical and biological production industries and causes serious environment problems. Porous materials, including MOFs (metal-organic frameworks) have been applied for efficient MB photocatalytic degradation. However, one of the main barriers to using most MOFs to break down aromatic organics is wide band gap energy, which means that the catalyst can exhibit high photocatalytic performance only under UVlight irradiation. Moreover, most MOFs usually show the poor water stability of frameworks, which tend to dissolve in water with total destruction. In this work we report about two new copper based MOFs with high photocatalytic properties for efficient MB degradation from wastewater under UV-light and natural sunlight. Time, required for 100% MB degradation, equals 7 minutes under UV (source 4 W 254 nm VL-4.LC UV-lamp) and 60 minutes under natural sunlight irradiation in the presence of H2O2. Crystal structure information is provided using single crystal X-ray diffraction data. The composition and comparative characteristics of MOFs are given using powder X-ray diffraction, UV–visible diffuse reflectance spectroscopy, UVvisible spectroscopy and Fourier-transform infrared spectroscopy.

Spent nuclear fuel is a very complex material because various elements such as fission products, transuranium elements and activation products are produced from initial fresh UO2 fuel after irradiation. These elements exist in UO2 with various forms and can change the structure and of physicochemical properties of UO2. These changes could provide the surface activation site that could enhance chemical reactions and corrosion processes, and would significantly affect the storage environment for long-term disposal of spent nuclear fuel. Therefore, it can be important to understand the characteristics of spent nuclear fuel to design reliable and safe geological repositories. However, it is too hard to study the characteristics of spent nuclear fuel, because it is a very complex material by itself and not easy to handle due to its radioactivity, and it is also difficult to independently understand the effects of each element. Therefore, a simulated spent nuclear fuel containing an element that forms a solid solution and epsilon particle was manufactured to understand the change in characteristics of each element. Most of the elements that form solid solutions are lanthanides or actinides and can change the structure of the UO2 lattice itself. The epsilon particles exist as metals at the grain boundaries of UO2. In this study, structural changes were measured using XRD, SEM, and Raman spectroscopy, and physical and chemical properties were also identified by measuring electrical conductivity and electrochemical properties. The results were summarized, and the effects of solid solution elements and epsilon particles on the structure and properties of UO2 matrix were compared and discussed.

Complexation of actinides and lanthanides with carboxylic organic ligands is known to facilitate migration of radionuclides from deep geological disposal systems of spent nuclear fuel. In order to examine the ligand-dependent structures of trivalent actinides and lanthanides, a series of Eu(III)-aliphatic dicarboxylate compounds, Eu2(oxalate)3(H2O)6, Eu2(malonate)3(H2O)6, and Eu2(succinate)3(H2O)2, were synthesized and characterized by using X-ray crystallography and time-resolved laser fluorescence spectroscopy. Powder X-ray diffraction results captured the transition of the coordination modes of aliphatic dicarboxylate ligands from side-on to end-on binding as the carbon chain length increases. This transition is illustrated in malonate bindings involving a combination of side-on and end-on modes. Strongly enhanced luminescence of these solid compounds, especially on the hypersensitive peak, indicates a low site symmetry of these solid compounds. Luminescence lifetimes of the compounds were measured to be increased, which is ascribed to the displacement of water molecules in the innersphere of Eu center upon bindings of the organic ligands. The numbers of remaining bound water molecules estimated from the increased luminescence lifetimes were in good agreement with crystal structures. The excitation-emission matrix spectra of these crystalline polymers suggest that oxalate ligands promote the sensitized luminescence of Eu(III), especially in the UV region. In the case of malonate and succinate ligands, charge transfer occurs in the opposite direction from Eu(III) to the ligands under UV excitation, resulting in weaker luminescence.

An important property of glass and ceramic solid waste forms is processability. Tellurite materials with low melting temperatures and high halite solubilities have potential as solid waste forms. Crystalline TiTe3O8 was synthesized through a solid-state reaction between stoichiometric amounts of TiO2 and TeO2 powder. The resultant TiTe3O8 crystal had a three-dimensional (3D) structure consisting of TiO6 octahedra and asymmetric TeO4 seesaw moiety groups. The melting temperature of the TiTe3O8 powder was 820℃, and the constituent TeO2 began to evaporate selectively from TiTe3O8 above around 840℃. The leaching rate, as determined using the modified American Society of Testing and Materials static leach test method, of Ti in the TiTe3O8 crystal was less than the order of 10-4 g·m-2·d-1 at 90℃ for durations of 14 d over a pH range of 2-12. The chemical durability of the TiTe3O8 crystal, even under highly acidic and alkaline conditions, was comparable to that of other well-known Ti-based solid waste forms.