• Economic and Environmental Geology
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• v.56 no.5
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• pp.565-580
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• 2023

In this study, we reviewed and summarized comprehensive roles and importance of natural analogue studies for demonstrating the safety and improving the reliability of the safety for the deep geological disposal of high-level radioactive waste. We also investigated domestic and foreign status of natural analogue studies in order to study and substantiate complex and various radionuclide behaviors in subsurface disposal environments. In addition, we investigated and uranium behaviors in groundwater and rock in uranium deposits including domestic uranium deposits in Ogcheon Metamorphic Belt and biogeochemical interactions in geological environments. Although there are many limitations and uncertainties in directly using the information and data for uranium behaviors obtained from uranium deposits in the disposal safety assessment, the information and data can be utilized in the disposal safety assessment and safety case construction both in qualitative and partly quantitative ways.

• Economic and Environmental Geology
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• v.27 no.6
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• pp.601-609
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• 1994

Uranium resources of Mongolia are generally confined to sediments deposited during Jurassic to Cretaceous volcanism. Territory of Mongolian uranium deposits is divided into four districts as follows; Mongol-Priargun, Gobi-Tamtsag, Hentii-Dauer, North-Mongolian. Potential uranium deposits were discovered by Airborne Gamma ray Spectrometric Survey(AGSM). One of them, Haraat deposit, which was interested to us, has been under detailed survey for exploitation by one of American companies, Concord company. The Erdes uranium mine is partly operated by about hundred Russian staffs at the open pit, while underground mining facilities such as the main hoist are almost closed. Ore minerals of the Erdes Mine are coffinite and pitchblende. Uranium content in ore ranges from 0.06% to 1%, averaging 0.2%. Ore reserves of uranium ore in the Dornod deposit including the Erdes Mine accounts 29,000 ton. It is reported that Uranium resources of Mongolia are 1,471,000 ton.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.41-48
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• 2010

Uranium deposits from an electrorefining process contain about 30% salt. In order to recover pure uranium and transform it into an ingot, the salts have to be removed from the uranium deposits. Major process variables for the salt distillation process of the uranium deposits are hold temperature and vacuum pressure. Effects of the variables on the salt removal efficiency were studied in the previous study[1]. By applying the Hertz-Langmuir relation to the salt evaporation of the uranium deposits, the evaporation coefficients were obtained at the various conditions. The operational conditions for achieving above 99% salt removal were deduced. The salt distilled uranium deposits tend to form the eutectic melt with iron, nickel, chromium for structural material of salt evaporator. In this study, we investigated the hold temperature limitation in order to prevent the formation of the eutetic melt between urnaium and other metals. The reactions between the uranium metal and stainless steel were tested at various conditions. And for enhancing the evaporation rate of the salt and the efficient recovery of the distilled salt, the thermal analysis of the salt distiller was conducted by using commercial CFX software. From the thermal analysis, the effect of Ar gas flow on the evaporation of the salt was studied.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2017.05a
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• pp.83-83
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• 2017

Electrorefining is a key step in pyroprocessing. The electrorefining process is generally composed of two recovery steps - the deposit of uranium onto a solid cathode and the recovery of the remaining uranium and TRU elements simultaneously by a liquid cadmium cathode. The solid cathode processing is necessary to separate the salt from the cathode since the uranium deposit in a solid cathode contains electrolyte salt. Distillation process was employed for the cathode processing. It is very important to increase the throughput of the salt separation system due to the high uranium content of spent nuclear fuel and high salt fraction of uranium dendrites. In this study, a mesh-covered crucible was investigated for the sat distillation of electrorefiner uranium deposits. A liquid salt separation step and a vacuum distillation step were combined for salt separation. The adhered salt in uranium deposits was efficiently removed in the mesh-covered crucible. The salt distiller was operated simply since repeated cooling - heating step was not necessary for the change of the crucible. The operation time could be reduced by the use of the mesh-covered crucible and the combined operation of the two steps. A method to preserve a vacuum level was proposed by double O-rings during the operation of the distiller with the mesh-covered crucible. After the salt distillation, the salt content was measured and was below 0.1wt% after the salt distillation. The residual salt after the salt distillation can be removed further during melting of uranium metal.

• Economic and Environmental Geology
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• v.56 no.5
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• pp.547-555
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• 2023

Due to enhanced precision in uranium isotope measurements with MC-ICP-MS, there has been a surge in studies concerning the naturally occurring uranium isotope ratio (²³⁸U/²³⁵U) and its associated fractionation processes. Several researchers have highlighted that the ²³⁸U/²³⁵U ratio, previously assumed to be constant, can vary by several per mil depending on different natural fractionation processes. This review paper outlines the uranium isotope values (δ²³⁸U) for major terrestrial reservoirs and their variations. It discusses the range of δ238U values and uranium isotope fractionation seen in uranium ore deposits, based on deposit type and ore-forming conditions. In conclusion, this paper emphasizes the importance of studies on uranium ore deposits. Such deposits serve as natural simulation models vital for designing high-level radioactive waste repository sites.

• The Korean Journal of Ecology
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• v.5 no.4
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• pp.137-142
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• 1982

From 1975 to 1981, the survey was carried out to find out radioecological effects of uranium ore deposits on natural vegetation in Koisan, Korea. The symptoms of spotty and mosaic chlorosis, and necrosis were observed in flowering plants in the areas of uranium ore deposits at Deok-Peung-Ri A, B, and C in Koisan. Although 13 species were found to be chlorosis and necrosis, foliages observed are small and very rare. The features of these symptoms closely resemble those occured by the effects of heavy meetals. The amount of transparent radiation throughout the depth of soils from uranium radiation sources decreases exponentially. The mean contents in leaves of spotty and mosaik chlorotic plants, and soils were 1.36~1.53 and 5.3~7.4 ppm, respectively.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2017.10a
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• pp.74-74
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• 2017

Electrorefining is a key step in pyroprocessing. The electrorefining process is generally composed of two recovery steps - the deposit of uranium onto a solid cathode and the recovery of the remaining uranium and TRU elements simultaneously by a liquid cadmium cathode. Uranium deposit recovered from the solid cathode is a dendritic powder. It is necessary to separate the adhered salt from the deposits prior to the consolidation of uranium deposit. The adhered salt is composed of lithium, potassium, uranium, and rare earth chlorides. Distillation process was employed for the cathode processing. One of the operation methods is distillation of the salt at low temperature ($900^{\circ}C$), and then melting of the deposit at high temperature to avoid a backward reaction. For the development of the salt distiller, the distillation behavior of the low vapor pressure chlorides should be studied. Rare earth chlorides in the adhered salt of uranium deposits have relatively low vapor pressures compared to the process salt (LiCl-KCl). In this study, the evaporation rates of the lanthanum and neodymium chlorides were measured for the salt separation from electrorefiner uranium deposits in the temperature range of $825{\sim}910^{\circ}C$. The evaporation rate of both chlorides increased with an increasing templerature. The evaporation rate of lanthanum chloride varied from 0.12 to $1.68g/cm^2/h$. Neodymium chloride was more volatile than lanthanum chloride. The evaporation rate of neodymium chloride varied from 0.20 to $4.55g/cm^2/h$. The evaporation rate of both chlorides are more than $1g/cm^2/h$ at $900^{\circ}C$. Even though the evaporation rates of both chlorides were less than that of the process salt, the contents of the lanthanide chlorides were small in the adhered salt. Therefore it can be concluded that $900^{\circ}C$ is suitable for the operation temperature of the salt distiller.

• Economic and Environmental Geology
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• v.15 no.2
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• pp.51-63
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• 1982

The uranium deposits of Bolivia are mainly found in the Altiplano and the Cordillera Oriental. In the Altiplano, many radioactive anomalies are detected in the Tertiary red beds and volcanic rocks. In the Cordillera Oriental, important anomalies are detected in the sedimentary rocks of Paleozoic, Mesozoic and Tertiary ages as well as in hydrothermal veins and syenitic rocks of Tertiary age. Classification of uranium deposits is attempted and their potentials are discussed. Widespread occurrence of various genetic types of uranium deposits in Bolivia draws attention of geologists on scientific and economic viewpoints. Mineralogical and genetic studies of important uranium deposits of Bolivia will be published in separate papers.

• Economic and Environmental Geology
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• v.13 no.4
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• pp.241-246
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• 1980

Some components in uranium-bearing formations which consist mainly of black shale, slate. and low grade coal-bearing formation of Ogcheon Belt were processed statistically in order to find out the geochemical correlations with uranium. Geochemical enrichment of uranium, vanadium and molybdenum in low grade coal-bearing formations and surrounding rocks is remarkable in the studied area. Geochemical correlation coefficient of uranium and molybdenum in the rocks displays about 0.6, and that of uranium and fixed carbon about 0.4. Uranium and vanadium in uranium-bearing low grade coals denote very high correlation with fixed carbon, which is considered to be responsible for enrichment of metallic elements, especially molybdenum. Close geochemical correlation of uranium-molybdenum couple in the rocks can be applied as a competent exploration guide to low grade uranium deposits of this area.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.85-89
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• 2010

The uranium ingot casting process is one of the steps which consolidate uranium deposits produced by electrorefiner as an ingot form in a pryprocessing technique. This paper introduces new design concept of the ingot casting equipment and the performance test results of the lab-scale ingot casting equipment fabricated based on the design concept. Casting equipment produces the uranium ingot by pouring an uranium melt into a mold by tilting a melting crucible. Also it is equipped with a cup which is able to continuously feed uranium deposits into a melting crucible. The productivity could be significantly enhanced by introducing the continuous operation concept.