Currently, non-volatile nuclides such as 94Nb, 99Tc, 90Sr, 55Fe, and 59/63Ni are used a sequential separation. In this study, we developed a separation for 99Tc and 90Sr by a carbonate precipitation. Sodium Carbonate (Na2CO3) was inserted in the aqueous sample from a Dry Active Waste (DAW) and a carbonate precipitation was produced. The precipitate is composed of di- or tri-valent element such as Co, Sr, Fe, Ni and the supernatant is composed of mono-valent element (Cs) and anion materials (ReO4 -, TcO4 -). In DAW, it was confirmed that the recovery of 90Sr (precipitate) and 99Tc (supernatant) were > 90%, respectively. The precipitate and supernatant separated by using a Sr-resin and an anion-exchange resin, respectively. The separated samples were measured by a Liquide Scintillation Counter (LSC, 90Sr) and Induced-Coupled Plasma-Mass Spectroscopy (ICPMS, 99Tc).

본 연구는 ‘암기조생’ 감귤 과실의 표면온도와 일사량 간의 상관관계를 분석하여 일소가 유발되는 과실 표면온도를 예측 하고 일소 발생을 경감시키고자 수행하였다. 이를 위해 기온 이 31℃일 때 30분 간격으로 5분 미세살수와 1% 탄산칼슘, 4% 카올린 용액을 10일 간격으로 3회 엽면살포하여 일소과 발생과 과실 품질을 조사하였다. 과실 표면온도는 일사량과 R = 0.788(p < 0.01)로 유의한 정의 상관관계를 나타냈으며 한 낮에는 기온보다 최고 16℃가 높았다. 과실 표면온도를 추정 하는 회귀식 y = 0.099 × (대기온도) + 0.018 × (일사량) + 20.779(R = 0.687, p < 0.01)을 도출하였다. 30분 간격으로 5 분 미세살수시 수관 내부 온도가 무처리보다 5.1℃ 낮았다. 일 소과 발생률은 미세살수구가 2.1%로 무처리구보다 2배 이상 낮았고 통계적으로 유의성을 나타냈으나, 과실 품질은 처리 간에 비슷하였다. 햇빛을 반사하거나 미세살수를 실시하여 과실 표면온도를 낮추면 일소 발생을 줄일 수 있을 것으로 보 인다.

Montmorillonite plays a key role in engineered barrier systems in the high-level radioactive waste repository because of its large sorption capacity and high swelling pressure. However, the sorption capacity of montmorillonite can be largely varied dependent on the surrounding environments. This study conducted the batch simulation for U(VI) sorption on Na-montmorillonite by utilizing the cation exchange and surface complexation coupled (2SP-NE-SC/CE) model and evaluated the effects of physicochemical properties (i.e., pH, temperature, competing cations, U(VI) concentration, and carbonate species) on U(VI) sorption. The simulation demonstrated that the U(VI) sorption was affected by physicochemical properties: the pH and temperature relate to aqueous U(VI) speciation, the competing cations relate to the cation exchange process and selectivity, the U(VI) concentration relates to saturation at sorption sites. For example, the Kd (L kg−1) of Na-montmorillonite represented the largest values of 2.7×105 L kg−1 at neutral pH condition and had significantly decreased at acidic pH<3, showing non-linear and diverse U(VI) sorption at the ranged pH from 2 to 11. Additionally, the U(VI) sorption on montmorillonite significantly decreased in presence of carbonate species. The U(VI) sorption for long-term in actual porewater chemistry and temperature of high-level radioactive waste repository represented that the sorption capacity of Na-montmorillonite was affected by various external properties such as concentration of competing cation, temperature, pH, and carbonate species. These results indicate that geochemical sorption capacity of bentonite should be evaluated by considering both geological and aquifer environments in the high-level radioactive waste repository.

It has been studied on the disposal area reduction for the used nuclear fuel by the management of high decay-heat nuclides, long-lived nuclides, and highly mobile nuclides. It was investigated on the management of the nuclides in KAERI. Strontium-90 is a high heat-generating nuclide in spent nuclear fuel. It is needed to separate the salt from the salt solution for the recovery of strontium after the chlorination of the strontium oxide in molten salt. Vacuum distillation was used for the separation of strontium from the molten salt. Potassium carbonate was chosen as a reactive distillation reagent for SrCl2 – LiCl – KCl system by the thermodynamic calculation. Reactive distillation experiments were carried out. The residual was mainly SrCO3 in the XRD analysis. It could be concluded that K2CO3 could be one of the suitable reagents for the reactive distillation. The salt in the long–lived nuclide powders should be removed to prepare the block for disposal. Experiments were carried out using W powders (surrogate) and U3O8 powders to develop a process for the removal of the residual salt from UOx powders. The salts were successfully removed from the W and U3O8 powders by distillation.

A method to effectively scavenge highly mobile radioiodide into a solid material was developed. Under an anaerobic condition, as copper(II) was strongly associated with bicarbonate (HCO3 −) in solution, malachite quickly formed, and then it was gradually transformed to a compact crystal of CuI (marshite) attracting iodide. The formation of CuI crystal was principally led by the spontaneous Cu-I redox reaction centering around the copper phase over the presence of sulfate (SO4 2−). The transformed CuI crystal was poorly soluble in water. Interestingly, this redox-induced iodide crystallization was rather promoted over the existence of anionic competitors (e.g., HCO3 − and SO4 2−). Unlike the conventional methods, these competing anions positively behaved in our system by supporting that the initial malachite was more apt to be reactive to largely attract highly mobile I−. Under practical environments, such a selective I− uptake and fixation into a crystalline form will be a promising way to effectively remove I− in a great capacity.

The reaction between Li2CO3 and Cl2 was investigated to verify its occurrence during a carbon-anode-based oxide reduction (OR) process. The reaction temperature was identified as a key factor that determines the reaction rate and maximum conversion ratio. It was found that the reaction should be conducted at or above 500℃ to convert more than 90% of the Li2CO3 to LiCl. Experiments conducted at various total flow rate (Q) / initial sample weight (W i) ratios revealed that the reaction rate was controlled by the Cl2 mass transfer under the experimental conditions adopted in this work. A linear increase in the progress of reaction with an increase in Cl2 partial pressure (pCl2) was observed in the pCl2 region of 2.03–10.1 kPa for a constant Q of 100 mL∙min−1 and W i of 1.00 g. The results of this study indicate that the reaction between Li2CO3 and Cl2 is fast at 650℃ and the reaction is feasible during the OR process.

The characteristics and morphology of precipitated calcium carbonate (PCC) particles produced by carbonation process with various experimental conditions are investigated in this study. The crystal structures of PCC formed by carbonation process are calcite and aragonite. The crystal structure of PCC particles synthesized without adipic acid additive is calcite only, regardless of the reaction temperature. Needle-like shape aragonite phase started to form at reactor temperature of 80°C with the adipic acid additive. Particle size of the single phase calcite PCC synthesized without adipic acid additive is about 1 ~ 3 μm, with homogenous distribution. The aragonite PCC also shows uniform size distribution. The reaction temperature and concentration of adipic acid additive do not show any significant effects on the particle size distribution. Aragonite phase grown to a large aspect ratio of needle-like shape showed relatively improved whiteness. The measured whiteness value of single calcite phase is about 95.95, while that of the mixture of calcite and aragonite is about 99.11.

The aim of this study was to improve dispersion stability of calcium carbonate (CaCO3) nanoparticles in aqueous medium using alkyl polyglucoside (APG). One hundred milligrams of CaCO3 nanoparticles was mixed with 30 mL of deionized water. Thereafter, APG was dissolved into the CaCO3 nanoparticle mixtures at approximate 0, 0.1, 0.3, 0.5, 0.7, and 0.9%, and subsequently, pH was adjusted to 7.0 and 10.0. Afterward, all CaCO3 nanoparticle mixtures were dispersed by ultrasonic processing treatment for 10 min. Dispersion stability and physicochemical properties of the CaCO3 nanoparticle mixtures were observed by measuring the change of absorbance and mean diameter for 96 h as well as the initial zeta-potential. As results, initial zeta-potentials of the CaCO3 nanoparticles in deionized water at pH 7.0 and 10.0 showed approximately +20 and 0, respectively. The positive surface charge at pH 7.0 had unfavorable impact on the adsorption of APG onto CaCO3 nanoparticles in the aqueous suspensions because APG is nonionic surfactant. Among all samples at pH 10, CaCO3 nanoparticles in 0.5% APG aqueous solution showed the smallest initial mean diameter and the slowest increase in mean diameter and decrease in absorbance. In conclusion, the pH 10.0 and 0.5% APG concentration was the most desirable condition in order to improve dispersion stability of CaCO3 nanoparticles in an aqueous medium.

Mineral filler is used for resin compounds, because it increases the stiffness and thermal stability of a resin compound, and it also cuts down the cost. Calcium carbonate, silica, magnesium oxide, and others are used as filler materials in general, and the type of filler material, the size, and content can affect the physical properties of compounds. Those factors also influence the viscosity of resin mixtures and the workability, and should be adjusted by changing the contents of the filler, which depends on the size. In this study, five kinds of ground calcium carbonate, which were different in size, were used to produce polyester compounds ; the physical properties were compared with the filler size and contents. The mechanical properties were measured by bending strength and tensile strength, and the heat deflection temperature was obtained for thermal stability.

본 연구에서는 액-액 반응에 의한 액상탄산화법을 이용하여 탄산칼슘을 제조하였다. MEA를 사용하여 습식화학수법의 셔틀메카니즘을 도입하였다. MEA 30% 수용액에 고농도 이산화탄소(A)와 배 기가스(B)를 사용하여 이산화탄소를 포집하였으며, 액상탄산화과정을 통해 슬러지 mg 당 0.35 mg의 이 산화탄소를 고정하였다. 최종생성물의 SEM 분석결과 탄산칼슘의 구조는 calcite가 혼합되어 있으나 대 부분 구형 vaterite가 생성되었다.

The following study aims to estimate the configuration ratio of the ion compounds that identifies the cause of fine dust and ways to reduce it. In this study, the physical and chemical properties of fine particles in a tunnel and the configuration form of ionic composition were interpreted to establish reasonable measurement for air quality management. Seasonal measurements were performed by collecting samples from the Mia sageori subway station. Chemical Mass Balance (CMB) model was used to estimate the configuration ratio of ions in this study. The results showed that the test performed outside showed about 56.4% of total ion, with (NH4)2SO4, NH4NO3, CaCO3 and NaCl showing concentrations of 2.138 μg/m3, 1.957 μg/m3, 1.697 μg/m3 and 1.600 μg/m3, respectively, while the results indoor had CaCO3, NH4NO3, (NH4)2SO4 and NaCl showing concentrations of 2.272 μg/m3, 2.204 μg/m3, 1.656 μg/m3 and 1.342 μg/m3, respectively, about 65.1% of total ion. During the usage of tunnel, it was found that CaCO3, NH4NO3, (NH4)2SO4 and MgCO3 showed concentrations of 3.464 μg/m3, 1.732 μg/m3, 1.698 μg/m3 and 0.582 μg/m3, respectively, total ion of 70.2% was presented.

본 연구에서는 이산화탄소 고정화에 있어 이산화탄소 전환을 위해 MEA를 이용한 습식화학흡 수법의 셔틀메카니즘을 도입하였다. 또한 알칼리 무기물질을 다량 함유한 산업부산물을 습식탄산화법을 이용해 처리하고자 하였다. 즉, 산업부산물의 화학적 처리를 통해 칼슘이온을 용출하였다. 산성물질을 이용한 용출상징수를 ICP로 분석한 결과, 칼슘이온이 최대 17,900 ppm(1.79%)을 확보하였다. 또한 MEA를 이용한 습식 흡수공정을 통해 상온, 상압조건의 이산화탄소 분위기에서 94%의 전환률을 얻었 다. 슬러지의 액상탄산화를 통해 슬러지 mg 당 0.175 mg의 이산화탄소를 고정하였으며, 최종생성물의 XRD 분석결과 일반적인 탄산칼슘의 결정구조인 calcite 형상을 확인하였다.

Carbonate-type organic electrolytes were prepared using propylene carbonate (PC) and dimethyl carbonate (DMC) as a solvent, quaternary ammonium salts, and by adding different contents of 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMImBF4). Cyclic voltammetry and linear sweep voltammetry were performed to analyze conducting behaviors. The surface characterizations were analyzed by scanning electron microscopy method and X-ray photoelectron spectroscopy. From the experimental results, increasing the EMImBF4 content increased the ionic conductivity and reduced bulk resistance and interfacial resistance. In particular, after adding 15 vol% EMImBF4 in 0.2 M SBPBF4 PC/DMC electrolyte, the organic electrolyte showed superior capacitance and interfacial resistance. However, when EMImBF4 content exceeded 15 vol%, the capacitance was saturated and the voltage range decreased.

A number of coated grains (spherical to elongated ones in shape) were collected from a small stream, Dijon, France. They were characterized by typical concentric lamination surrounding broken twigs, and were thus identified as concentric precipitation on plant twigs. Within carbonate coatings of the plant twigs, two morphological groups including, eukaryotic green algae (Vaucheria sp.) and cyanobacteria (Scytonema sp. and Rivularia sp.) were detected, which form carbonate crystals that are surrounding their filaments. The filaments could have triggered carbonate precipitation by photosynthetic removal of CO2 causing the increase of alkalinity of the water, and by supporting their sheaths as nucleation sites. Such encrusted twigs were found from 70 meters downstream, in which temperature and pH were measured as 11.1˚C and 8.18, respectively. These water chemistries (11.1˚C and pH 8.18), with the aid of microbial photosynthesis, were likely to provide a suitable condition for carbonate precipitation on the twigs.

본 연구에서는 분쇄공정에 의한 나노화에 따른 이화학적 특성 변화를 밝히기 위하여 칼슘 나노분말의 이화학적 특성을 칼슘 마이크로분말과 비교 분석하였다. 형태분석 위해 전자현미경을 이용한 결과 칼슘 나노입자의 크기는 약 100 nm였고 칼슘 마이크로 입자의 크기는 100 nm-3 μm 이었으며 칼슘 나노 및 마이크로 입자들의 형태는 육면체 모양의 표면이 날카롭고 거친 것으로 관찰되었다. 입도분석기를 이용해 크기 분포를 분석한 결과 칼슘의 농도가 0.5 mg/mL 일 때, 칼슘 나노 및 마이크로분말의 평균 입자크기는 각각 440.2±73.8 nm, 547.1±105.3 nm이었으며 칼슘의 농도가 1.0 mg/mL 일 때, 칼슘 나노 및 마이크로분말의 평균 입자크기는 각각 388.8±123.2 nm, 1001.9±160.4 nm이었다. 제타전위는 칼슘 나노 분말이 -9.94±1.78 mV이였으며 칼슘 마이크로 분말은 -2.42±2.38 mV으로 시료 두 가지 모두 수용액 상태에서 불안정 하지만 나노 분말이 상대적으로 안정한 것으로 나타났다. 칼슘 나노 및 마이크로 분말의 비표면적은 각각 6.99 m2/g, 4.26 m2/g으로 나노 분말이 더 높게 측정되었다. 겉보기 밀도는 칼슘 나노(0.47±0.01 g/mL)와 마이크로(0.45±0.03 g/mL)분말의 차이가 거의 없었으나, 다짐밀도에서 칼슘 마이크로 분말이 0.97±0.02 g/mL로 칼슘 나노분말 0.81±0.02 g/mL 보다 더 높았다. 안식각은 칼슘 나노분말이 35.40±1.32o로 칼슘 마이크로 분말의 안식각 39.37±2.46o 보다 작아 유동성이 큰 것으로 분석되었다. 본 연구 결과들은 분쇄 공정에 따른 나노화에 의한 칼슘 나노분말을 비롯한 다양한 무기질 나노분말의 이화학적 특성 변화를 밝힐 수 있는 연구로 확대될 수 있는 가능성이 있다.