• 청정기술
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• 제20권3호
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• pp.212-217
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• 2014

재생공정에서 황화 된 탈황흡수제의 재생을 위하여 산소는 산화제로 사용되었다. 재생공정에서 미량의 미 반응 산소는 직접 황 회수 공정으로 유입된다. 그러나, $SO_2$ 환원을 위한 반응성은 미 반응 산소의 다양한 이유에 의해서 저하된다. $SO_2$ 환원을 위한 반응성 실험을 위해 Sn-Zr계 촉매가 사용되었으며, $SO_2$와 $O_2$는 각각 5.0 vol%와 4.0 vol%로 고정하였고 $300-450^{\circ}C$와 1-20 atm에서 수행되었다. 본 연구에서는 고온건식 탈황공정의 직접 황 회수공정에 유입되는 미 반응산소에 의한 촉매반응성 저하에 미치는 영향을 조사하였다. $SO_2$ 환원으로 생성된 원소 황은 미 반응산소에 의해서 재산화되고, redox반응기구에서 Sn-Zr계 촉매의 빈 격자 산소자리가 미 반응산소에 의해서 재산화되므로 $SO_2$ 전화율은 감소되는 것으로 판단된다. 한편 환원제로써 공급된 CO는 미 반응산소에 의해서 산화되어 연소열에 의해 촉매 충전 층 온도가 상승되기도 한다. 결과적으로 충전 층의 빠른 온도상승은 활성 물질을 소결시켜 촉매의 비활성화를 초래하게 된다.

• 분석과학
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• 제13권3호
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• pp.309-314
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• 2000

리튬 용융염($LiC+Li_2O$) 내에 미량으로 존재하는 핵분열생성물을 유도결합 플라스마 원자방출분광기(ICP-AES)를 이용하여 분석하였다. 분석대상 원소 중 감도가 가장 좋은 파장을 선택해 이들 파장에서 리튬 500, 1,000, 2,000 mg/L에 따른 분광학적 간섭 여부를 확인한 결과, 분석원소중 0.1 mg/L 이하의 Y, Nd, Sr, La, Eu의 방출세기는 리튬의 농도가 2,000 mg/L까지 증가시켜도 분광학적 간섭을 받지 않은 반면, Mo, Ba, Ru, Pd, Rh, Zr, Ce는 10% 에서 50% 이상 분광학적 간섭과 매트릭스에 의한 스펙트럼 방해가 나타났다. 리튬 매질로부터 미량 금속원소들을 군분리하기 위하여 모의 용융염 용액을 조제해 암모니아수를 가한 후 분리하고 다시 산처리하여 얻은 용액을 ICP-AES로 회수율을 측정하였다. 분석원소 중 Ru, Y, Rh, Zr, Nd, Ce, La, Eu의 회수율은 90% 이상인 반면 Mo, Ba, Pd, Sr는 낮은 회수율을 보여주었으며, 가해준 암모니아수 양이 증가할수록 회수율이 증가하는 경향을 보였다.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.109-114
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• 2020

This work presents the results of laboratory scale tests of the CARBOFLUOREX (CARBOnate FLUORide EXtraction) process - a novel technology for the recovery of U and Pu from the solid fluorides residue (fluorination ash) of Fluoride Volatility Method (FVM) reprocessing of spent nuclear fuel (SNF). To study the oxidative leaching of U from the fluorination ash (FA) by Na₂CO₃ or Na₂CO₃-H₂O₂ solutions followed by solvent extraction by methyltrioctylammonium carbonate in toluene and purification of U from the fission products (FPs) impurities we used a surrogate of FA consisting of UF₄ or UO₂F₂, and FPs fluorides with stable isotopes of Ce, Zr, Sr, Ba, Cs, Fe, Cr, Ni, La, Nd, Pr, Sm. Purification factors of U from impurities at the solvent extraction refining stage reached the values of 10⁴-10⁵, and up to 10⁶ upon the completion of the processing cycle. Obtained results showed a high efficiency of the CARBOFLUOREX process for recovery and separating of U from FPs contained in FA, which allows completing of the FVM cycle with recovery of U and Pu from hardly processed FA.

• 열처리공학회지
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• 제10권2호
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• pp.81-92
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• 1997

The effect of alloying elements, precipitate size, its distribution, and dislocation substructure resulted from warm rolling or cold rolling in the superplastic Al-Mg alloy system was investigated. One of the major requirements for fine structure superplasticity is that the grain size should be very small. Fine grain structure is controlled by the dislocation substructure and the dynamic recrystallization during hot or warm working. The recovery of Al-Mg base alloys was constrained resulting in relatively high dislocation density when the alloys were warm rolled. In particular, Al-Mg-Zr alloy exhibited the smallest sub-grain size among Al-Mg alloys containing Mn, Cu, Zr as a third element. The Al-Mg-Mn alloy cold rolled 80% after hot rolling showed the maximun strain rate sensitivity exponent, m, of 0.75 under strain rate of $7.1{\times}10^{-4}/s$ at $500^{\circ}C$. The elongation of the alloys was limited in spite of high m values due to large dispersoids containing appreciable amount of Fe impurities.

• Nuclear Engineering and Technology
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• 제48권1호
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• pp.16-25
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• 2016

In severe loss of coolant accidents (LOCA), similar to those experienced at Fukushima Daiichi and Three Mile Island Unit 1, the zirconiumalloy fuel claddingmaterials are rapidlyheateddue to nuclear decay heating and rapid exothermic oxidation of zirconium with steam. This heating causes the cladding to rapidly react with steam, lose strength, burst or collapse, and generate large quantities of hydrogen gas. Although maintaining core cooling remains the highest priority in accident management, an accident tolerant fuel (ATF) design may extend coping and recovery time for operators to restore emergency power, and cooling, and achieve safe shutdown. An ATF is required to possess high resistance to steam oxidation to reduce hydrogen generation and sufficient mechanical strength to maintain fuel rod integrity and core coolability. The initiative undertaken by Electric Power Research Institute (EPRI) is to demonstrate the feasibility of developing an ATF cladding with capability to maintain its integrity in $1,200-1,500^{\circ}C$ steam for at least 24 hours. This ATF cladding utilizes thin-walled Mo-alloys coated with oxidation-resistant surface layers. The basic design consists of a thin-walled Mo alloy structural tube with a metallurgically bonded, oxidation-resistant outer layer. Two options are being investigated: a commercially available iron, chromium, and aluminum alloy with excellent high temperature oxidation resistance, and a Zr alloy with demonstratedcorrosionresistance.Asthese composite claddings will incorporate either no Zr, or thin Zr outer layers, hydrogen generation under severe LOCA conditions will be greatly reduced. Key technical challenges and uncertainties specific to Moalloy fuel cladding include: economic core design, industrial scale fabricability, radiation embrittlement, and corrosion and oxidation resistance during normal operation, transients, and severe accidents. Progress in each aspect has been made and key results are discussed in this document. In addition to assisting plants in meeting Light Water Reactor (LWR) challenges, accident-tolerant Mo-based cladding technologies are expected to be applicable for use in high-temperature helium and molten salt reactor designs, as well as nonnuclear high temperature applications.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.812-818
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• 2024

The volume and toxicity of radioactive waste can be decreased by separating the components of high-level liquid waste according to their properties. An impregnated silica-based adsorbent was prepared in this study by combining N,N,N',N',N",N"-hexa-n-octylnitrilotriacetamide (HONTA) extractant, N',N'-di-n-hexyl-thiodiglycolamide (Crea) extractant, and macroporous silica polymer composite particles (SiO₂-P). The performance of platinum-group metals adsorption and separation on prepared (HONTA + Crea)/SiO₂-P adsorbent was then assessed together with that of co-existing metal ions by batch-adsorption and chromatographic separation studies. From the batch-adsorption experiment results, (HONTA + Crea)/SiO₂-P adsorbent showed high adsorption performance of Pd(II) owing to an affinity between Pd(II) and Crea extractant based on the Hard and Soft Acids and Bases theory. Additionally, significant adsorption performance was observed toward Zr(IV) and Mo(VI). Compared with studies using the Crea extractant, the high adsorption performance of Zr(IV) and Mo(VI) is attributed to the HONTA extractant. As revealed from the chromatographic experiment results, most of Pd(II) was recovered from the feed solution using 0.2 M thiourea in 0.1 M HNO₃. Additionally, the possibility of recovery of Zr(IV), Mo(VI), and Re(VII) was observed using the (HONTA + Crea)/SiO₂-P adsorbent.

• 한국전기전자재료학회논문지
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• 제14권7호
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• pp.551-556
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• 2001

In this work, the recovery of etching damage in the etched PZT thin film with $O_2$ annealing has been studied. The PZT thin films were etched as a function of Cl$_2$/Ar and additive CF$_4$ into Cl$_2$(80%) /Ar(20%). the etch rates of PZT thin films were 1600$\AA$/min at Cl$_2$(80%)/Ar(20%) and 1970 $\AA$/min at 30% additive Cf$_4$ into Cl$_2$(80%)/Ar(20%). In order to recover the characteristics of etched PZT thin films, the etched PZT thin films were annealed in $O_2$ atmosphere at various temperatures. From the hysteresis curves, ferroelectrical properties are improved by $O_2$ annealing process. The improvement of ferroelectric behavior is consistent with the increase of the (100) and (200) PZT phase revealed by x-ray diffraction (XRD). From x-ray photoelectron spectroscopy (XPS) analysis, intensities of Pb-O, Zr-O and Ti-O peak increase and the chemical residue peak is reduced by $O_2$ annealing. From the atomic force microscopy (AFM) images. it shows that the surface morphology of re-annealed PZT thin films after etching is improved.

• 공업화학
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• 제18권2호
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• pp.155-161
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• 2007

본 연구에서는 $SnO_2-ZrO_2$(Sn/Zr = 2/1) 촉매 상에서의 CO에 의한 $SO_2$ 환원반응에 대한 반응온도, 공간속도, [CO]/[$SO_2$] 몰비 등의 반응조건의 최적화를 위한 반응특성을 조사하였다. $300{\sim}550^{\circ}C$의 반응온도, $5000{\sim}30000cm^3/g_{-cat}{\cdot}h$의 공간속도, 1.0~4.0 의 [CO]/[$SO_2$] 몰비 등 다양한 반응조건 범위에서 CO에 의한 $SO_2$ 환원반응에 대한 영향을 살펴본 결과, 최적 반응조건으로 반응온도, 공간속도, [CO]/[$SO_2$] 몰비는 각각 $325^{\circ}C$, $10000cm^3/[g_{-cat}{\cdot}h]$, 2.0이었다. 이 때 $SO_2$ 전환율은 약 99% 이상이었으며, 원소 황 선택도는 95% 이상이었다. 또한 CO에 의한 $SO_2$ 환원반응에서 수분에 대한 영향을 조사한 결과, 수분함량이 2.0~6.0 vol%인 범위에서 수분의 함량이 높을수록 $SO_2$ 전환율 및 원소 황 선택도가 감소됨과 동시에 반응성이 저하됨을 알 수 있었다. 2 vol%의 수분이 함유된 반응조건에서 반응온도와 [CO]/[$SO_2$] 몰비를 각각 $300{\sim}400^{\circ}C$ 및 1.0~3.0으로 변화시킨 결과, 반응온도와 [CO]/[$SO_2$] 몰비가 각각 $340^{\circ}C$와 2.0인 조건에서 가장 높은 반응성을 얻었다. 이 때 $SO_2$ 전환율이 약 90%였으며, 원소 황 선택도는 약 87%였다

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 반도체재료
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• pp.8-11
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• 2001

In this study. the recovery of plasma induced damage in the etched PZT thin film with $O_2$ re-annealing have been investigated. The PZT thin films were etched as a function of $Cl_2/Ar$ and additive $CF_4$ into $Cl_{2}(80%)/Ar(20)%$. The etch rates of PZT thin films were $1600\dot{A}/min$ at $Cl_{2}(80%)/Ar(20)%$ gas mixing ratio and $1970\dot{A}/min$ at 30 % additive $CF_4$ into $Cl_{2}(80%)/Ar(20)%$. The etched profile of PZT films was obtained above 70 by SEM. In order to recovery properties of PZT thin films after etching, the etched PZT thin films were re-annealed at various temperatures in $O_2$ atmosphere. From the hysteresis curves, ferroelectrical properties are improved by $O_2$ re-annealing process. The improvement of ferroelectric behavior at annealed sample is consistent with the increase of the (100) and (200) PZT phase revealed by x-ray diffraction (XRD). From XPS analysis, intensity of Pb-O, Zr-O and Ti-O peak are increased and the chemical residue peak is reduced by $O_2$ re-annealing. The ferroelectric behavior consistent with the dielectric nature of TixOy is recovered by $O_2$ recombination during rapid thermal annealing process. From AFM images, it shows that the surface roughness of re-annealed sample after etching is improved.

• 자원리싸이클링
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• 제18권5호
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• pp.26-36
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• 2009

폐스크랩으로부터 Ru을 회수하기 위한 전처리 공정으로 질산을 침출제로 사용하여 Pb, Ba, Zn, Al, Bi, Ag Fe, Co, Zr, Si 등의 침출 거동을 고찰하고, 이들 성분들을 제거 할 수 있는 최적조건을 도출하고자 하였다. 실험결과 고액농도 250 g/L에서 10-15% 질산 용액으로 약 90%의 Pb를 침출시켜 제거할 수 있었다. 또한 Ba의 경우도 Pb와 유사한 침출 거동을 나타내었으며, 기타 금속원소들 중 Zn, Al, Bi, Ag, Fe, Co, Zr은 질산농도 증가에 따라 침출율이 증가하나 질산농도가 10% 이상에서는 침출율이 거의 일정하였다. 한편, Ru의 경우는 약 100 ppm 이하로 침출율이 미미하였고, 질산침출 후 잔사중에 Ru이 50%이상으로 농축됨을 알 수 있었다.