• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2880-2886
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• 2020

A small leak occurring on the surface of a fuel rod due to damage exposes UO₂ to a steam atmosphere. During this time, fission gas trapped inside the fuel rod leaks out, and the gas leakage can be increased due to UO₂ oxidation. Numerous studies have focused on the steam oxidation and its thermodynamic calculation in UO₂. However, the thermodynamic calculation of the UO₂ oxidation in a pressurized water reactor (PWR) environment has not been studied extensively. Moreover, the kinetics of the oxidation of UO₂ pellet also has not been investigated. Therefore, in this study, the thermodynamics of UO₂ oxidation under steam injection due to a damaged fuel rod in a PWR environment is studied. In addition, the diminishing radius of the UO₂ pellet with time in the PWR environment was calculated through an experiment simulating the initial time of steam injection at the puncture.

• 대한금속재료학회지
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• 제46권10호
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• pp.652-661
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• 2008

Reduction of NOx in emission gas, improvement of engine efficiency, and extension of warranty period has made demands for developing materials more corrosively resistant to the inner-muffler environments or predicting the lifetime of materials used in muffler more precisely. The corrosion inside muffler has been explained with condensate corrosion mainly though thermal oxidation experiences prior to condensate corrosion. Hence, the aim of this study is to describe how the thermal oxidation affects the corrosion of stainless steel exposed to the inner-muffler environments. Auger electron spectroscopy and electrochemical tests were employed to analyze oxide scale and to evaluate corrosion resistance, respectively. Thermal oxidation has different role of condensate corrosion depending on the temperature: inhibiting condensate corrosion below $380^{\circ}C$ and enhancing condensate corrosion above $380^{\circ}C$. The low temperature oxidation causes to form compact oxide layer functioning a barrier for penetrating condensate into a matrix. Although though thermal oxidation caused chromium-depleted layer between oxide layer and matrix, the enhancement of the condensate corrosion in high temperature oxidation resulted from corrosion-induced crevice formed by oxide scale rather than corrosion in chromium-depleted layer. It was proved by aids of anodic polarization tests and measurements of pitting corrosion potentials. By the study, the role of high temperature oxidation layer affecting the condensate corrosion of stainless steels used as muffler materials was well understood.

• 대한환경공학회지
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• 제27권5호
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• pp.513-518
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• 2005

망간 산화물 촉매, 망간-세륨 산화물 촉매에서 톨루엔의 촉매 산화에 대하여 조사 하였다. XRD, TGA, 톨루엔-TPR 분석을 통해 촉매의 특성을 조사하였다. 톨루엔 산화반응에 있어서 망간 18.2 wt.% 세륨 10.0 wt.%이 적절한 비율인 것으로 나타났다. 그리고 세리아가 망간 산화물에서의 활성을 증진 시키는 것으로 보여진다. XRD결과 $MnO_2$가 황성 자리인 것으로 추측된다. TGA 톨루엔-TPR결과 세리아가 격자 산소의 이동성, 활성자리의 적절한 상화 상태, 저온에서의 환원능력 및 활성자리의 재산화 능력을 증진시키는 것으로 사료된다.

• 환경영향평가
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• 제30권2호
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• pp.132-139
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• 2021

과산소산(peroxy-acid)을 산화제로 사용하여 현장 오염토양내 존재하는 다환방향족탄화수소의 산화분해 효과를 알아보기 위하여 실험실 규모의 연구를 진행하였다. 대상 토양의 토성은 19.2 %의 토양 유기물을 포함한 pH 6.8의 사양토(sandy loam)로 확인되었으며 토양 내 다환방향족탄화수소 중 벤조(a)피렌(benzo(a)pyrene)의 농도가 평균 2.23 mg/kg으로 국내 토양환경보전법의 1 지역 우려 기준치의 3배 정도 높게 나타났다. 따라서 벤조(a)피렌 오염 토양에 대하여 유기산과 과산화수소를 이용한 과산소산 산화(peroxy-acid oxidation)처리에 의한 토양내 벤조(a)피렌의 농도 저감효과를 유기산의 종류와 유기산 및 과산화수소의 농도조건별로 평가하였다. 선정된 유기산 중 프로피온산(propionic acid)의 산화 효과가 가장 큰 것으로 확인되었으며 토양 중 벤조(a)피렌의 농도를 최종적으로 1 지역 우려 기준치 이하로 저감하였다.

• Membrane and Water Treatment
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• 제9권3호
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• pp.189-194
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• 2018

Electrochemical reduction of nitrate was studied using Zn, Cu and (Ir+Ru)-Ti cathodes and Pt/Ti anode in a cell divided by an ion exchange membrane. During electrolysis, effects of the different cathode types on operating parameters (i.e., voltage, temperature and pH), nitrate removal efficiency and by-products (i.e., nitrite and ammonia) formation were investigated. Ammonia oxidation rate in the presence of NaCl was also determined using the different ratios of hypochlorous acid to ammonia. The operating parameter values were similar for all types of cathode materials and were maintained relatively constant. Nitrate was well reduced and converted mostly to ammonia using Zn and Cu cathodes. Ammonia, produced as a by-product of nitrate reduction, was oxidized in the presence of NaCl in the electrochemical process and the oxidation performance was enhanced upon increasing the hypochlorous acid-to-ammonia ratio to 1.09:1. Zn and Cu cathodes promoted the nitrate reduction to ammonia and the produced ammonia was finally removed from solution by reacting with hypochlorite ions. Using Zn or Cu cathodes, instead of noble metal cathodes, in the electrochemical process can be an alternative technology for nitrate-containing wastewater treatment.

• 한국수소및신에너지학회논문집
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• 제28권4호
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• pp.392-400
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• 2017

An experimental study was conducted to investigate behavior of steel surface oxidation with characteristics of the combustion. The excess entalphy combustion in porous media system was applied to implement the direct radiation heating system. The surface oxidation thickness (SOT) of fuel-lean was thicker than the SOT of fuel-rich. Also, the SOT was increased by increasing residence time. Detailed explanations were given by SEM and EDS analysis.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.715-720
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• 2014

A Cu(II) complex with an three nitrogens and one sulfur coordination environment was synthesized and characterized. Its redox potential was observed at 0.483 V vs. NHE, very similar to that of a Cu-containing fungal enzyme, galactose oxidase, which catalyzes the oxidation of alcohols to corresponding aldehydes with the concomitant reduction of molecular oxygen to water. The Cu(II) complex selectively oxidizes the benzylic alcohols using TEMPO/$O_2$ under mild reaction conditions to corresponding aldehydes without forming any over-oxidation product. Moreover, the catalyst can be recovered and reused multiple times for further oxidation reactions, thus minimizing the waste generation.

• 한국전기전자재료학회논문지
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• 제16권3호
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• pp.181-185
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• 2003

Influence of post gate oxidation anneal on Negative Bias Temperature Instability (NBTI) of PMOSFE has been investigated. At oxidation anneal temperature raised above 950$^{\circ}$C, a significant improvement of NBTI was observed which enables to reduce PMO V$\_$th/ shift occurred during a Bias Temperature (BT) stress. The high temperature anneal appears to suppress charge generations inside the gate oxide and near the silicon oxide interface during the BT stress. By measuring band-to-band tunneling currents and subthreshold slopes, reduction of oxide trapped charges and interface states at the high temperature oxidation anneal was confirmed.

• Bulletin of the Korean Chemical Society
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• 제12권1호
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• pp.35-39
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• 1991

The catalytic activity of $Nd_{1-x}Sr_xCoO_{3-y}$, $0{\leq}x{\leq}0.75$ and $0.001{\leq}y{\leq}0.103$, on the oxidation of carbon monoxide has been investigated from the structure analyses of the catalysts by X-ray diffraction and infrared spectroscopy and the measurements of the oxidation and adsorption rates of carbon monoxide. The catalytic activity is found to be correlated with Sr substitution (x) and nonstoichiometry (y). The oxidation power of carbon monoxide increases continuously with increasing Sr substitution without oxygen, but increases with Sr substitution up to x = 0.25 and then is almost constant at larger x values up to x = 0.75 with oxygen. This change of catalytic activity is explained by the oxidation-reduction properties of the catalyst due to the variation of nonstoichiometry.

• 한국환경과학회지
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• 제13권3호
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• pp.245-250
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• 2004

The SBR(Sequencing Batch Reactor) process is ideally suited to treat high loading wastewater due to its high dilution rate. SBR operates by a cycle of periods consisting of filling, reacting, settling, decanting and idling. The react phases such as aeration or non-aeration, organic oxidation, nitrification, denitrification and other bio-logical reactions can be achieved in a reactor. Although the whole reactions can be achieved in a SBR with time distributing, it is hard to manage the SBR as a normal condition without recognizing a present state. The present state can be observed with nutrient sensors such as ${NH_{4}}^{+}-N$, ${NO_{2}}^{-}-N$, ${NO_{3}}^{-}-N} and ${PO_{4}}^{ 3-}-P.$ However, there is still a disadvantage to use the nutrient sensors because of their high expense and inconvenience to manage. Therefore, it is very useful to use common on-line sensors such as DO, ORP and pH, which are less expensive and more convient. Moreover, the present states and unexpected changes of SBR might be predicted by using of them. This study was conducted to get basic materials for making an inference of SBR process from ORP(oxidation reduction potential) of synthetic wastewater. The profiles of ORP, DO, and pH were under normal nitrification and denitrification were obtained to compare abnormal condition. And also, nitrite and nitrate accumulation were investigated during reaction of SBR. The bending point on ORP profile was not entirely in the low COD/NOx ratio condition. In this case, NOx was not entirely removed, and minimum ORP value was presented over -300mV. Under suitable COD/NOx ratio which complete denitrification was achieved, ORP bending point was observed and minimum ORP value was under -300m V. Under high COD/NOx ratio, ORP bending point was not detected at the first subcycle because of the fast denitrification and minimum ORP value was under -300mV at the time.