• Corrosion Science and Technology
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• v.22 no.6
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• pp.457-465
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• 2023

Irradiation-assisted stress corrosion cracking (IASCC) is one of the main degradation mechanisms of austenitic stainless steels, which are used as reactor internal materials. Slow strain rate testing (SSRT) has been widely applied to evaluate the IASCC initiation characteristics of proton-irradiated tensile specimens. Tensile specimens require low surface roughness for micro-crack observation, and electropolishing is the most important specimen pre-treatment process used for this. In this study, optimal electropolishing conditions were examined through analyzing results of polarization experiments and surface roughness measurements after electropolishing. Corrosion cell and electropolishing equipment were fabricated for polarization tests and electropolishing experiments using SSRT specimens. The experimental parameters were electropolishing time, current density, electrolyte temperature, and stirring speed. The optimal electropolishing conditions for SSRT tensile specimens made of type 316 stainless steel were evaluated as a polishing time of 180 seconds, a current density of 0.15 A/cm², an electrolyte temperature of 60 ℃, and a stirring speed of 200 RPM.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.6
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• pp.447-452
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• 2011

In this study, the polymeric membrane module is used as a diffuser and an image analysis technique based on visual information is applied to get bubble characteristics. The bubble size generated passed through polymeric membrane module was smaller from 30 to 64% than that of air stone, and bubble volume over 70% was ranged from 0.2 to 0.82 mm. But over 80% the bubbles from air stone diffuser ranged from 0.77 to 1.08 mm. The air stone and polymeric membrane module used as diffuser for a flotation system. The floc size inside the flotation reactor using air stone diffuser was bigger than that of the polymeric membrane module, which means that the micro-bubbles generated from polymeric membrane module could provide better opportunities for collisions between colloidal particles than those from air stone diffuser. Therefore, there is a possibility to apply the polymeric membrane module as a diffuser to increase the removal efficiency in the flotation process. Also, the image analysis technique used in this study could be applied as a useful analytical tool for acquisition of an information about the bubble characteristic.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.985-989
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• 1999

Silica($SiO_2$) thin film was synthesized by a low pressure metal organic chemical vapor deposition(LPMOCVD) using organic silane compound. Triethyl orthosilicate was used as a source material. Operation pressure was 1~100 torr at outlet of the reactor and deposition temperature was $600{\sim}900^{\circ}C$. The experimental results showed that the high reaction temperature and high source gas concentration led to higher growth rate of $SiO_2$. The step coverage of films on micro-scale trenches was fairly good, which resulted from the phenomena that the condensed oligomers flow into the trenches. We estimated a reaction path that the source gas polymerizes and produces oligomers (dimer, trimer, tetramer, etc.), which diffuse and condense on the solid surface. The chemical species in the gas phase at the outlet of reactor tube were analyzed by quadrapole mass spectrometer. The peaks, assigned to be monomer, dimer of source gas and geavier molecules, were observed at 650 or $700^{\circ}C$. At higher temperature($900^{\circ}C$), the peaks of the heavy molecules disappeared, because almost all the source gas and intermediate(polymerized oligomer) molecules were oxidized or condensed on colder tube wall.

• Clean Technology
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• v.27 no.4
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• pp.325-331
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• 2021

In this study, bio-carbons were produced by activation process from unused biomass (Grade 3 wood pellet and spent coffee grounds) to determine the removal performance of formaldehyde and acetaldehyde. The activation experiments were conducted in a fixed bed reactor using CO₂ as an activation agent. The temperature of the activation reactor and input of CO₂ were 900 ℃ and 1 L min^-1 for all the experiments. The maximum BET surface area of about 788 m² g^-1 was obtained for bio-carbon produced from Grade 1 wood pellet, whereas about 544 m² g^-1 was achieved with bio-carbon produced from spent coffee grounds. In all the experiments, the bio-carbons produced were mainly found to have micro-porous nature. A lower ash amount in raw material was favored for the high surface area of bio-carbons. In the removal test of formaldehyde and acetaldehyde, the bio-carbon produced from spent coffee grounds showed excellent adsorption performance compared with woody biomass (Grade 1 wood pellet and Grade 3 wood pellet). In addition, the comparative experiment of commercial impregnated activated carbon and bio-carbon produced from spent coffee grounds was conducted. In terms of formaldehyde removal performance, the commercial impregnated bio-carbon was excellent, while bio-carbon produced from spent coffee grounds was excellent in acetaldehyde removal.

• Journal of Environmental Science International
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• v.20 no.10
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• pp.1329-1336
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• 2011

The objectives of this study are to examine the processing of oils contamination soil by means of using a micronano-bubble soil washing system, to investigate the various factors such as washing periods, the amount of micro-nano bubbles generated depending on the quantity of acid injection and quantity of air injection, to examine the features involved in the elimination of total petroleum hydrocarbons (TPHs) contained in the soil, and thus to evaluate the possibility of practical application on the field for the economic feasibility. The oils contaminated soil used in this study was collected from the 0~15 cm surface layer of an automobile junkyard located in U City. The collected soil was air-dried for 24 hours, and then the large particles and other substances contained in the soil were eliminated and filtered through sieve No.10 (2 mm) to secure consistency in the samples. The TPH concentration of the contaminated soil was found to be 4,914~5,998 mg/kg. The micronano-bubble soil washing system consists of the reactor, the flow equalization tank, the micronano- bubble generator, the pump and the strainer, and was manufactured with stainless material for withstanding acidic phase. When the injected air flow rate was fixed at 2 L/min, for each hydrogen peroxide concentrations (5, 10, 15%) the removal percents for TPH within the contaminated soil with retention times of 30 minutes were respectively identified as 4,931 mg/kg (18.9%), 4,678 mg/kg (18.9%) and, 4,513 mg/kg (17.7%). And when the injected air flow rate was fixed at 2 L/min, for each hydrogen peroxide concentrations (5, 10, 15%) the removal percents for TPH within the contaminated soil with retention times of 120 minutes were respectively identified as4,256 mg/kg (22.3%), 4,621 mg/kg (19.7%) and 4,268 mg/kg (25.9%).

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.2
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• pp.125-133
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• 2004

Fission products of DUPIC (Direct Use of Spent PWR Fuel in CANDU Reactors) fuel, irradiated in HANARO research reactor with 61 ㎾/m of maximum linear power and 1,770 ㎿d/tU of average burn-up, was characterized by EPMA(Electron Probe Micro Analyzer). In order to find accurate characterization, the analysis results by EPMA of fresh simulated DUPIC fuel containing fission products as chemicals were compared with that of wet chemical analysis. The metallic precipitates observed at the center of the fresh simulated DUPIC fuel were about 1 $\mu\textrm{m}$ in size and their major components by EPMA were Mo-53.89 at.%, Ru-37.40 at.%, and Pd+Rh-8.71 at.%. Established procedure through the fresh simulated DUPIC fuel was applied to the irradiated DUPIC fuel. Observed size of metallic precipitates were 2∼2.5 $\mu\textrm{m}$ and their compositions were Mo-47.34 at.%, Ru-46 at.%, and Pd+Rh-6.65 at.%. What are uncommon things for this experiment, special treatment for improving the conductivity was attempted to the specimen and the conditions of exact irradiation of electron beam to small metallic precipitate were suggested.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.734-739
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• 2009

Characteristics of pyrolysis, partial oxidation, combustion of chlorella, which is one species of micro-algae, were determined by using thermobalance reactor(I.D. 5.5 cm, Height 1 m). Effect of reaction temperature($500{\sim}800^{\circ}C$), water content in chlorella(0~60%), and oxygen content(0~21vol%) on thermal decomposition of chlorella were also determined and analyzed to investigate the kinetic characteristics of pyrolysis, partial oxidation and combustion. As the temperature and partial pressure increases, the carbon conversion increases. In case of pyrolysis, carbon conversion and reactivity sharply decreased with increasing moisture content. However, carbon conversion and reactivity decreased at 60% water content in case of partial oxidation and combustion. As reaction temperature and oxygen content increased, carbon conversion increased and the combustion reaction rate equation for chlorella has been presented. $\frac{dX}{dt}=(7.41{\times}10^{-1})$exp$\left(-\frac{19600}{RT}\right)(P_{O_{2}})^{0.209}(1-X)^{2/3}$.

• Land and Housing Review
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• v.3 no.3
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• pp.299-305
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• 2012

Various types of bio wood chip for fermentation-extinction of food waste was investigated by comparing their different pore structure with the performance of weight loss rate and microbial activity. The fermentation-extinction of food waste with bio wood chip was examined by adding 700~1,500g of food waste every day during 15 days to the fermentation-extinction reactor with condition of $30{\sim}50^{\circ}C$ temperature and 30~70% humidity, where 1,500g of bio wood chips were existed. The bio wood chips used in this experiment were categorized into 4 different types; microbial-mixing type(A biochip), macro pore type(B biochip) under $2{\mu}m$ of pore size, micro pore type of wood-chips(C biochip) under $0.1{\mu}m$ of pore size, viscous & sticky type(D biochip). As a result, A, B, C, D bio wood chip exhibited 85%, 63%, 92%, 73% weight loss of food waste with fermentation-extinction. The maximum weight loss of food waste was obtained at the fermentation-extinction experiments by using C bio wood chip. On the other hands, the maximum ratio of ATP to COD and TN was obtained from $3.00{\times}10^{-10}$ and $2.31{\times}10^{-11}$ in the case of C bio wood chip, comparing with other types of bio wood chip. Consequently, the performance of weight loss rate was affected with the micro pore structure of bio wood chip which have an advantage of extensive microbial activity space in the fermentation-extinction of food waste.

• Journal of the Korean GEO-environmental Society
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• v.13 no.2
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• pp.41-47
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• 2012

The purpose of this study was to determine optimum condition for the cultivation of Chlorella sp. FC-21 using red light emitting diodes (LED). Specific growth rate and cell concentration were measured for the reactors at the illuminations of different light intensity of red LED. Under the illumination of red LED, specific growth rate increased as light intensity increased but cell concentrations decreased. To determine beneficial effect of aeration to cell cultivation, micro-air bubbles were aerated at 0.7 vvm in the reactor at the illumination of red LED. Two and ten times greater specific growth rate and cell concentration were obtained when aeration was applied. In case of blowing of carbon dioxide, pH of culture medium decreased below to pH 3, which resulted in decreases of cell concentration. From this study, we found that red LED with aeration were the most appropriate light source for the cultivation of Chlorella sp. FC-21.

• Membrane and Water Treatment
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• v.9 no.5
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• pp.327-334
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• 2018

The nano/micro composites with highly porous surface area have attracted of great interest, particularly the synthesis of porous and thin film sheets of high performance. In this paper, an easy method of cost-effective synthesis of thin film ceramic fiber membranes based on Hydroxyapatite, and activated carbon by turned into studied to be applied within the service-facilitated the transport of radioactive waste such as $^{90}Sr$, $^{137}Cs$ and $^{60}Co$) as activated product of radioisotopes from ETRR-2 research reactor and dissolved in 3M $HNO_3$, across a thin flat-sheet supported liquid membrane (TFSSLM). Radionuclides are transported from alkaline pH values. The presence of sodium salts in the aqueous media improves in $HNO_3$, the lowering of permeability because the initial $HNO_3$ concentration is improved. The study some parameters on the thin sheet ceramic supported liquid membrane. EDTA as stripping phase concentration, time of extraction and temperature were studied. The study of maximum permeability of radioisotopes for all parameters. The pertraction of a radioactive waste solution from nitrate medium were examined at the optimized conditions. Under the optimum experimental 98.6-99.9% of $^{90}Sr$, 79.65-80.3% of $^{137}Cs$ and $^{60}Co$ 45.5-55.5% in 90-110 min with were extracted in 10-30 min, respectively. The process of diffusion in liquid membranes is governed by the chemical diffusion process.