• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.14 no.2
• /
• pp.101-112
• /
• 2016

This study investigated the removal of Sr, which was one of the high radioactive nuclides, by adsorption with Barium (Ba) impregnated 4A zeolite (BaA) from high-radioactive seawater waste (HSW). Adsorption of Sr by BaA (BaA-Sr), in the impregnated Ba concentration of above 20.2wt%, was decreased by increasing the impregnated Ba concentration, and the impregnated Ba concentration was suitable at 20.2wt%. The BaA-Sr adsorption was added to the co-precipitation of Sr with $BaSO_4$ precipitation in the adsorption of Sr by 4A (4A-Sr) within BaA. Thus, it was possible to remove Sr more than 99% at m/V (adsorbent weight/solution volume)=5 g/L for BaA and m/V >20 g/L for 4A, respectively, in the Sr concentration of less than 0.2 mg/L (actual concentration level of Sr in HSW). It shows that BaA-Sr adsorption is better than 4A-Sr adsorption in for the removal capacity of Sr per unit gram of adsorbent, and the reduction of the secondary solid waste generation (spent adsorbent etc.). Also, BaA-Sr adsorption was more excellent removal capacity of Sr in the seawater waste than distilled water. Therefore, it seems to be effective for the direct removal of Sr from HSW. On the other hand, the adsorption of Cs by BaA (BaA-Cs) was mainly performed by 4A within BaA. Accordingly, it seems to be little effect of impregnated Ba into BaA. Meanwhile, BaA-Sr adsorption kinetics could be expressed the pseudo-second order rate equation. By increasing the initial Sr concentrations and the ratios of V/m, the adsorption rate constants ($k_2$) were decreased, but the equilibrium adsorption capacities ($q_e$) were increasing. However, with increasing the temperature of solution, $k_2$ was conversely increased, and $q_e$ was decreased. The activation energy of BaA-Sr adsorption was 38 kJ/mol. Thus, the chemical adsorption seems to be dominant rather than physical adsorption, although it is not a chemisorption with strong bonding form.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.16 no.1
• /
• pp.49-58
• /
• 2018

For the immobilization of high-radioactive nuclides such as Cs and Sr by high-temperature thermal decomposition, this study was carried out to investigate the phase transformation with calcined temperature by using TGA (thermogravimetric analysis) and XRD (X-ray diffraction) in the Cs-adsorbed CHA (chabazite zeolite of K type)-Cs and CHA-PCFC (potassium cobalt ferrocyanide)-Cs zeolite system, and Sr-adsorbed 4A-Sr and BaA-Sr zeolite system, respectively. In the case of CHA-Cs zeolite system, the structure of CHA-Cs remained at up to $900^{\circ}C$ and recrystallized to pollucite ($CsAlSi_2O_6$) at $1,100^{\circ}C$ after undergoing amorphous phase at $1,000^{\circ}C$. However, the CHA-CFC-Cs zeolite system retained the CHA-PCFC-Cs structure up to $700^{\circ}C$, but its structure collapsed in $900{\sim}1,000^{\circ}C$, and then transformed to amorphous phase, and recrystallized to pollucite at $1,100^{\circ}C$. In the case of 4A-Sr zeolite system, on the other hand, the structure of 4A-Sr maintained up to $700^{\circ}C$ and its phase transformed to amorphous at $800^{\circ}C$, and recrystallized to Sr-feldspar ($SrAl_2Si_2O_8$, hexagonal) at $900^{\circ}C$ and to $SrAl_2Si_2O_8$ (triclinic) at $1,100^{\circ}C$. However, the BaA-Sr zeolite system structure began to break down at below $500^{\circ}C$, and then transformed to amorphous phase in $500{\sim}900^{\circ}C$ and recrystallized to Ba/Sr-feldspar (coexistence of $Ba_{0.9}Sr_{0.1}Al_2Si_2O_8$ and $Ba_{0.5}Sr_{0.5}Al_2Si_2O_8$) at $1,100^{\circ}C$. All of the above zeolite systems recrystallized to mineral phase through the dehydration/(decomposition) ${\rightarrow}$ amorphous ${\rightarrow}$ recrystallization with increasing temperature. Although further study of the volatility and leachability of Cs and Sr in the high-temperature thermal decomposition process is required, Cs and Sr adsorbed in each zeolite system are mineralized as pollucite, Sr-feldspar and Ba/Sr-feldspar. Therefore, Cs and Sr seen to be able to completely immobilize in the calcining wasteform/(solidified wasteform).

• Korean Chemical Engineering Research
• /
• v.50 no.2
• /
• pp.229-237
• /
• 2012

Phosphorus was incorporated into Co/$Al_2O_3$ catalyst for FTS by impregnating an acidic precursor, phosphoric acid, in ${\gamma}-Al_2O_3$ support to improve the mechanical strength, the hydrothermal stability of the catalyst particle, and the catalytic performance as well. Surface characterization techniques such as FT-IR revealed that $AlPO_4$ phase was generated on the surface of the P-modified catalyst. The addition of phosphorus was found to alleviate the interaction between cobalt and alumina surface, and to increase reducibility of catalyst. The catalytic activity such as $C_{5+}$ productivity and turnover frequency (TOF) was calculated to evaluate catalytic performance. The influence of calcination temperature of the $Al_2O_3$ containing 2 wt.% P on the catalytic performance was also investigated. Through hydrothermal stability test and XRD analysis, the P-modified catalyst had strong resistant to the pressurized and hot $H_2O$. The mechanical strength of the P-modified catalyst was also examined through an in-house fluidized-bed vessel, and it was found that the catalyst fragmentation could be successfully suppressed with P. Taken as a whole, the best performance was shown to be at 1~2 wt.% P in alumina and at the calcination temperature of $500^{\circ}C$.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.7 no.2
• /
• pp.93-100
• /
• 2009

This study has been carried out to look into the characteristics of an oxidative-dissolution of fission products (FP) co-dissolved with uranium (U) in a $(NH_4)_2CO_3$ carbonate solution. Simulated FP-oxides which contained 12 components have been added to the solution to examine their dissolution characteristics. It is found that $H_2O_2$ is an effective oxidant to minimize the oxidative-dissolution of FP. In the 0.5 M $(NH_4)_2CO_3$-0.5 M $H_2O_2$ solution, some elements such as Re, Te, Cs and Mo seem to be dissolved together with U, while 98${\pm}$2% for Re and Te, 94${\pm}$2% for Cs, and 29${\pm}$2 % for Mo are dissolved for 2 hours. It is revealed that dissolution rates of Re, Te and Cs are high (completely dissolved within 10${\sim}$20 minutes) due to their high solubility in the $(NH_4)_2CO_3$ solution regardless of the addition of $H_2O_2$, and independent of the concentrations of $Na_2CO_3$ and $H_2O_2$. However, the dissolution ratio of Mo seems to be slightly increased with time and about 33 % for 4 hours, indicating a very slow dissolution rate and also independent of the $(NH_4)_2CO_3$ concentration. It is found that the most important factor for the oxidative-dissolution of FP is the pH of the solution and an effective dissolution is achieved at a pH between 9${\sim}$10 in order to minimize the dissolution of FP.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.14 no.3
• /
• pp.223-234
• /
• 2016

This study aimed to the adsorption-removal of high- radioactive iodide (I) contained in the initially generated high-radioactive seawater waste (HSW), with the use of AgX (Ag-impregnated X zeolite). Adsorption of I by AgX (hereafter denoted as AgX-I adsorption) was increased by increasing the Ag-impregnated concentration in AgX, and its concentration was suitable at about 30 wt%. Because of AgCl precipitation by chloride ions contained in seawater waste, the leaching yields of Ag from AgX (Ag-impregnated concentration : about 30~35 wt%) was less than those in distilled water (< 1 mg/L). AgX-I adsorption was above 99% in the initial iodide concentration ($C_i$) of 0.01~10 mg/L at m/V (ratio of weight of adsorbent to solution volume)=2.5 g/L. This shows that efficient removal of I is possible. AgX-I adsorption was found to be more effective in distilled water than in seawater waste, and the influence of solution temperature was insignificant. Ag-I adsorption was better described by a Freundlich isotherm rather than a Langmuir isotherm. AgX-I adsorption kinetics can be expressed by a pseudo-second order rate equation. The adsorption rate constants ($k_2$) decreased by increasing $C_i$, and conversely increased by increasing the ratio of m/V and the solution temperature. This time, the activation energy of AgX-I adsorption was about 6.3 kJ/mol. This suggests that AgX-I adsorption is dominated by physical adsorption with weaker bonds. The evaluation of thermodynamic parameters (a negative Gibbs free energy and a positive Enthalpy) indicates that AgX-I adsorption is a spontaneous reaction (forward reaction), and an endothermic reaction indicating that higher temperatures are favored.

• Journal of Technology Innovation
• /
• v.26 no.4
• /
• pp.199-232
• /
• 2018

There are increasing needs for understanding and fathoming of business management environment through big data analysis at industrial and corporative level. The research using the company disclosure information, which is comprehensively covering the business performance and the future plan of the company, is getting attention. However, there is limited research on developing applicable analytical models leveraging such corporate disclosure data due to its unstructured nature. This study proposes a text-mining-based analytical model for industrial and firm level analyses using publicly available company disclousre data. Specifically, we apply LDA topic model and word2vec word embedding model on the U.S. SEC data from the publicly listed firms and analyze the trends of business topics at the industrial and corporate levels. Using LDA topic modeling based on SEC EDGAR 10-K document, whole industrial management topics are figured out. For comparison of different pattern of industries' topic trend, software and hardware industries are compared in recent 20 years. Also, the changes of management subject at firm level are observed with comparison of two companies in software industry. The changes of topic trends provides lens for identifying decreasing and growing management subjects at industrial and firm level. Mapping companies and products(or services) based on dimension reduction after using word2vec word embedding model and principal component analysis of 10-K document at firm level in software industry, companies and products(services) that have similar management subjects are identified and also their changes in decades. For suggesting methodology to develop analysis model based on public management data at industrial and corporate level, there may be contributions in terms of making ground of practical methodology to identifying changes of managements subjects. However, there are required further researches to provide microscopic analytical model with regard to relation of technology management strategy between management performance in case of related to various pattern of management topics as of frequent changes of management subject or their momentum. Also more studies are needed for developing competitive context analysis model with product(service)-portfolios between firms.