• Journal of environmental and Sanitary engineering
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• v.15 no.1
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• pp.77-87
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• 2000

Several new ion exchange resins have been synthesized from chloromethyl styrene-l,4-divinylbenzine with 1%, 2%, 10% and 20%-crosslink and macrocyclic ligands of cryptand type by interpolymerization method. The adsorption characteristics and the pH, time, solvents and concentration dependence of the adsorption of metal ions by this resin were studied. The correlation between the separation characteristics of uranium and transition metal on the resins and the stability constants of complexes with macrocyclic ligands have been examined. The resins were very stable in both acidic and basic media and have good resistance to heat. The $UO_2^{2+}$ was not adsorbed on the resins below pH 3.0, but the power of adsorption of $UO_2^{2+}$ increased rapidly above pH 4.0. The optimum equilibrium time for adsorption of metallic ions was two hours and adsorptive power decreased in proportion to crosslink size of the resins and order of dielectric constants of solvents used and the selective sequence for metal cations was in the order of $UO_2^{2+}$, $Ni{2+}$ and $Nd{3+}$.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.167-179
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• 2024

This study explores the feasibility of employing (U, Th)-based accident tolerant fuels (ATFs), specifically (_0.8UO₂, _0.2ThO₂), (_0.8UN, _0.2ThN), and (_0.8UC, _0.2ThC). The investigation assesses the overall performance of these proposed fuel materials in comparison to the conventional UO₂, focusing on deep neutronic and thermal-hydraulic (Th) analyses. Neutronic analysis utilized the MCNPX code, while COMSOL Multiphysics was employed for thermal-hydraulic analysis. The primary objective of this research is to overcome the limitations associated with traditional UO₂ fuel by exploring alternative fuel materials that offer advantages in terms of abundance and potential improvements in performance and safety. Given the limited abundance of UO₂, long-term sustainable nuclear energy production faces challenges. From a neutronic standpoint, the U-Th based fuels demonstrated remarkable fuel cycle lengths, except (_0.8UN, _0.2ThN), which exhibited the minimum fuel cycle length and, consequently, the lowest fuel burn-up. Regarding thermal-hydraulic performance, (_0.8UN, _0.2ThN) exhibited outstanding performance with significant margins against fuel melting compared to the other materials. Overall, when considering the integrated performance, the most favourable results were obtained with the use of the (_0.8UC, _0.2ThC) fuel configurations. This study contributes valuable insights into the potential benefits of (U, Th)-based ATFs as a promising avenue for enhanced nuclear fuel performance.

• Nuclear Engineering and Technology
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• v.35 no.4
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• pp.299-308
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• 2003

Fabrication technique of $(Th,U)O_2$ pellets has been investigated. Powder mixtures of $ThO_2\;and\;UO_2$ were milled in two different ways-dry and wet milling. Milled powder was compacted and sintered to $(Th,U)O_2$ pellets. The wet-milled powder leads to a $(Th,U)O_2$ pellet having a high sintered density and uniform distribution of U and Th, compared to the dry-milled powder. The sintered density of a $(Th,U)O_2$ pellet tends to decrease by increasing the content of $ThO_2$. The thermal conductivity of $ThO_2\;and\;(Th,U)O_2$ pellets was measured by the laser flash method. The thermal conductivity of the $ThO_2$ pellet is higher than that of the $UO_2$ pellet, and the thermal conductivities of $(Th,U)O_2$ pellets containing $65wt\%\;and\;35wt\%\;ThO_2$ pellets are lower than that of the $UO_2$ pellet.

• Advances in environmental research
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• v.4 no.2
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• pp.135-142
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• 2015

In this study, we evaluated the adsorption/desorption of uranium (U) in pure soil environment using continuous column reactor. We additionally investigated the adsorption/desorption mechanism of U on vivianite surface in molecular scale using quantum calculation. We observed that below $0.1{\mu}M$ of U was detected after 20 d from U injection ($1{\mu}M$) in adsorption test. However, all of absorbed U was detached from vivianite surface in 24 h by injection of CARB solution ($1.44{\times}10^{-2}M\;NaHCO_3$ and $2.8{\times}10^{-3}M\;Na_2CO_3$). Based on exchange energy calculation, we found that $UO_2(CO_3)_2{^{2-}}$ and $UO_2(CO_3)_3{^{4-}}$ species have higher repulsive energy than $UO_2(OH)_2$ species. The results obtained from this study could be applied to predict the behavior of uranium in contaminated and remediation sites.

• Journal of the Korean Chemical Society
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• v.52 no.5
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• pp.468-475
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• 2008

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.470-475
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• 1996

사용후핵연료 장기 건식저장시 여러가지 저장조건에서 사용후핵연료 피복관 및 사용후핵연료 ($UO_2$)에 대한 장기 건전성을 종합적으로 평가할 수 있는 SIECO 코드를 개발하였다. 건식저장 시스템은 사용후핵연료를 헬륨 및 공기분위기하에서 TN-24P 건식 저장용기에 장기 저장할 경우로 하였으며 피복관의 최대 표면온도는 COBRA-SFS코드를 사용하여 계산하였고, 열유동 해석결과를 바탕으로 SIECO코드를 이용하여 핵연료 연소도 및 냉각기간, 냉각매체에 따른 최대 건식저장 허용온도를 피복관의 열화 및 $UO_2$ 산화의 관점에서 계산하였다.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2003.10a
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• pp.206-210
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• 2003

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.149.1-149
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• 2002

• Applied Chemistry for Engineering
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• v.3 no.2
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• pp.312-317
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• 1992

The interaction of dioxouranium(VI) (uranyl) ion with nitrate ion has been studied by $^{17}O$ NMR spectroscopy. The $^{17}O$ resonance of uranyl oxygen atoms(uranyl oxygens hereafter) of $UO_2NO_3{^+}$ was at lower field than that of uranyl ion. The stability constants of $UO_2NO_3{^+}$ were obtained from the variation of $^{17}O$ chemical shifts with nitrate-ion concentration at 5, 15, 25, $35^{\circ}C$ and depend on the ionic strength. Thermodynamic parameters calculated from temperature dependence of the stability constants were as follows : ${\Delta}H=-(27.2{\pm}1.7)kJ\;mol^{-1}$ and ${\Delta}S=-(110{\pm}7)JK^{-1}mol^{-1}$. There was a linear relationship between the enthalpy and entropy for 1:1 complex formation of the uranyl ion with a variety of anionic ligands.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.138-144
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• 2013

Electrochemical reductions of $UO_2$ at various anode-to-cathode distances (1.3, 2.3, 3.2, 3.7 and 5.8 cm) were carried out to investigate the effect of the anode-to-cathode distance on the electrochemical reduction rate. The geometry of the electrolysis cell in this study, apart from the anode-to-cathode distance, was identical for all of the electrolysis runs. Porous $UO_2$ pellets were electrolyzed by controlling a constant cell voltage in molten $Li_2O-LiCl$ at $650^{\circ}C$. A steel basket containing the porous $UO_2$ pellets and a platinum plate were used as the cathode and anode, respectively. The metallic products were characterized by means of a thermogravimetric analyzer, an X-ray diffractometer and a scanning electron microscope. The electrolysis runs conducted during this study revealed that a short anode-to-cathode distance is advantageous to achieve a high current density and accelerate the electrochemical reduction process.