• Nuclear Engineering and Technology
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• 제34권2호
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• pp.176-185
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• 2002

A 4-bundle shift refuelling method of CANDU6 F/H (Fuel Handling) System is analyzed to assess the operational flexibility and capacity of F/H system. The current 8-bundle shift refuelling scheme requires to refuel eight fuel bundles from a single fuel channel, and to refuel 14 fuel channels in a week on average assuming that the reactor is in a steady state. The analysis showed that the 4-bundle shift refuelling method increases F/M (Fuelling Machine) duty cycle and operator load. However, the fuellin’g method change from the 8- to 4-bundle shift refuelling ill not require additional team of operators. A marginal increase in the maintenance cost may be resulted in by the change of fuelling method and the increase of fatigue usage factors requires some components to be replaced during the FM lifetime.

• Nuclear Engineering and Technology
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• 제49권5호
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• pp.1095-1099
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• 2017

A fission source can act as a stabilization element in coupled Monte Carlo simulations. We have observed this while studying numerical instabilities in nonlinear steady-state simulations performed by a Monte Carlo criticality solver that is coupled to a xenon feedback solver via fixed-point iteration. While fixed-point iteration is known to be numerically unstable for some problems, resulting in large spatial oscillations of the neutron flux distribution, we show that it is possible to stabilize it by reducing the number of Monte Carlo criticality cycles simulated within each iteration step. While global convergence is ensured, development of any possible numerical instability is prevented by not allowing the fission source to converge fully within a single iteration step, which is achieved by setting a small number of criticality cycles per iteration step. Moreover, under these conditions, the fission source may converge even faster than in criticality calculations with no feedback, as we demonstrate in our numerical test simulations.

• 조명전기설비학회논문지
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• 제20권9호
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• pp.70-77
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• 2006

We have fabricated an integrated three-phase flux-lock type SFCL, which consists of an YBCO($YB_a2Cu_3O_7$) thin film and a flux-lock reactor wound around an iron core of each phase. In order to apply the SFCL in a real power system, fault analyses for the three-phase system are essential. The short-circuit currents were effectively limited by adjusting the numbers of winding of each secondary coil and their winding directions. The flux flow generated in the iron core cancelled out under the normal operation due to the parallel connection between primary and secondary windings. However, the flux-lock type SFCL with same iron core was operated just after the fault due to the flux generating in the iron core. To analyze the current limiting characteristics, the additive polarity winding was compared with the subtractive one in the flux lock reactor. Whenever a single line-to-ground fault occurred in any phase, the peak value of the line current of the fault phase in the additive polarity winding increased up to about 12.87 times during the first-half cycle. On the other hand, the peak value in the subtractive polarity winding increased up to about 34.07 times under the same conditions. This is because the current flow between the primary and the secondary windings changed to additive or subtractive status according to the winding direction. We confirmed that the current limiting behavior in the additive polarity winding was more effective for a single-line-to-ground fault

• Nuclear Engineering and Technology
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• 제5권2호
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• pp.137-149
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• 1973

중성자 방사화 및 방사능 계측에 관계하는 핵데타를 세밀히 연구검토하여 망간을 불순물로 함유하고 있는 철선을 단일비교체로 한 중성자 방사화분석법을 발전시켰다. 유효반응 단면적의 변화를 원자로 내부 스펙트럽의 열외 중성자의 비율과 같은 스펙트럼 지표 및 그 외 다른 변수의 함수로 검토하였으며 조사위치에서 중성자 스펙트럽의 변위로 생기는 오차를 토의하였다. 각원소의 이미 아는양을 취하여 단일비교체와 함께 조사한 다음 본법에 의해서 그 함량을 산출하여서 원래 취한 양과 비교하였다. 그 결과 우연오차는 일반적인 비교법으로 얻은 오차보다 크지 않았으나 계통적 오차는 대략 20%이내였다. 본법을 모나자이트 중에 함유된 14개 희토류 원소의 정량과 표준배추시료 중에 있는 다른 7개의 원소정량에 적용하였다. 그 결과 분석치는 만족할만한 재현성을 나타내었으며 종래의 비교법으로 얻을 수 있는 정도의 정착성으로 이들 원소를 분석할 수 있었다.

• 한국환경과학회지
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• 제24권3호
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• pp.317-322
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• 2015

The photocatalytic decomposition characteristics of toluene, acetone, and methyl mercaptan (MM) by UV reactor installed with $TiO_2$-coated perforated plane were studied. The removal efficiency of single toluene, acetone, and MM vapor was increased with increasing oxygen concentration, but decreased with increasing inlet concentration. Elimination capacity of single toluene, acetone, and MM vapor was obtained to be $628g/m^3{\cdot}day$, $1,041g/m^3{\cdot}day$, and $2,158g/m^3{\cdot}day$, respectively. Also, the photocatalytic decomposition of binary vapor consisted of toluene and acetone, toluene and MM, acetone and MM were observed. Elimination capacity of toluene mixed with acetone, toluene mixed with MM, acetone mixed with toluene, acetone mixed with MM, MM mixed with toluene, and MM mixed with acetone was $327g/m^3{\cdot}day$, $512g/m^3{\cdot}day$, $128g/m^3{\cdot}day$, $266g/m^3{\cdot}day$, $785g/m^3{\cdot}day$ and $883g/m^3{\cdot}day$, respectively. The inhibitory effect of acetone was higher than MM in photocatalytic decomposition of toluene, the inhibitory effect of toluene was higher than MM photocatalytic decomposition of acetone, and the inhibitory effect of toluene was higher than acetone in photocatalytic decomposition of MM.

• 상하수도학회지
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• 제19권6호
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• pp.720-727
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• 2005

This study was performed to advance nitrogen removal efficiency by employing an single biofilter packed with granular sulfur, which consists of nitrification occurring at upper part and denitrification at lower part of the reactor. Continuos nitrification/denitrification was carried out with different alkalinity sources, which were $NaHCO_3$ and $CaCO_3$(limestone). In the downflow nitrification/denitrification biofilter packed with granular sulfur, first, terms for nitrogen removal was decided. As results, nitrification and denitrification rate with NaHCO3 at 0.85 kg $NH_4^+-N/m^3{\cdot}d$ were accomplished $0.80kg\;N/m_3{\cdot}d$, $0.43kg\;N/m^3{\cdot}d$, respectively. In the sulfur/limestone packed downflow nitrification/denitrification biofilter, sulfur and limestone were mixed packed, preliminary test showed sulfur/limestone mixing ratio was 3:1 and that was ideal. In the result, nitrification and denitrification rate at $0.7kg\;NH_4^+-N/m^3{\cdot}d$ were accomplished$0.65kg\;N/m^3{\cdot}d$, $0.34kg\;N/m^3{\cdot}d$, respectively. In general, employing granular sulfur can be implemented for only denitrification, but this system can accomplish nitrification as well as denitrification in a single reactor even though low carbon concentration was present in influent limiting to nutrient removal process. This biofilter system of limestone and granular sulfur packed together can successfully apply for nutrient removal effectively.

• 대한기계학회논문집A
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• 제34권9호
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• pp.1217-1225
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• 2010

소듐을 냉각재로 사용하는 고속로의 증기발생기에서는 소듐과 물의 화학적 반응을 최소화하는 것이 중요한 문제이다. 소듐과 물의 반응 가능성을 줄여 증기발생기의 신뢰성을 향상시키기 위한 한가지 방안으로 이중벽관을 전열관으로 사용하는 증기발생기를 개발하고 있다. 이 증기발생기에서 중요한 현안은 이중벽관에서의 열전달 성능을 향상시키는 문제와 원자로 운전 중에 소듐과 물 반응사고가 일어나기 전에 전열관의 파손을 감지하는 기술을 개발하는 것이다. 이 논문에서는 이 현안을 극복할 수 있는 방안을 제시하였고, 이 기술을 활용하여 증기발생기의 개념을 설계하였다. 또한 이 개념에 적용되는 이중벽관을 설계 및 예비 제작하여 기계적 시험을 수행하였다.

• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1733-1739
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• 2017

Molecular dynamics simulations were performed to investigate the uniaxial tensile properties of nanocrystalline $U_{0.5}Th_{0.5}O_2$ solid solution with the Born-Mayer-Huggins potential. The results indicated that the elastic modulus increased linearly with the density relative to a single crystal, but decreased with increasing temperature. The simulated nanocrystalline $U_{0.5}Th_{0.5}O_2$ exhibited a breakdown in the Halle-Petch relation with mean grain size varying from 3.0 nm to 18.0 nm. Moreover, the elastic modulus of $U_{1-y}Th_yO_2$ solid solutions with different content of thorium at 300 K was also studied and the results accorded well with the experimental data available in the literature. In addition, the fracture mode of nanocrystalline $U_{0.5}Th_{0.5}O_2$ was inclined to be ductile because the fracture behavior was preceded by some moderate amount of plastic deformation, which is different from what has been seen earlier in simulations of pure $UO_2$.

• 조명전기설비학회논문지
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• 제24권5호
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• pp.145-151
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• 2010

전압 불평형은 수용가 설비에서 상당히 중요한 전기 품질의 하나로 간주되고 있다. 전압은 송전선로 계통에서는 평형에 가깝지만, 수용가에서의 전압 레벨은 시스템 임피던스의 불평형과 단상 부하의 고르지 못한 배분 등으로 인해 불평형이 될 수 있다. 콘덴서는 역률 보상으로도 사용되며, 비선형 부하에서 발생하는 고조파를 저감하기 위해 리액터와 함께 사용되고 있다. 전압 불평형이 존재할 경우 전류 불평형으로 콘덴서에서는 용량변화가 일어난다. 콘덴서와 리액터를 함께 사용하는 경우 사고 발생이 높은 편이다. 그래서 콘덴서 설비에 전압 불평형이 존재할 경우 전압, 전류 그리고 용량의 변화가 어떻게 진행되는지 확인하는 것이 매우 중요하다. 본 연구에서는 전압 불평형률이 존재할 경우 콘덴서 단독운전과 리액터의 부착시 전압, 전류 및 용량의 크기가 규정에서 제시한 범위 이내인지를 계산하였다.

• 한국가스학회지
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• 제2권3호
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• pp.60-69
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• 1998

저온 플라즈마를 이용한 메탄 직접 전환반응은 진공에서 메탄만을 원료로 마이크로웨이브나 라디오 주파수(R.F)등의 에너지를 가하여 플라즈마 상태로 반응시켜 에틸렌, 에탄, 아세틸렌 등의 C2 화합물을 생성하는 방법이다. 이러한 직접적인 메탄 전환의 장점은 산소를 가하지 않으므로 산소에 의한 부생성물이 없는 점과 저온 플라즈마를 이용하므로 저에너지 공정이라는 것을 들 수 있다. 본 연구에서는 마이크로웨이브와 라디오 주파수(R.F)를 이용하여 저온 플라즈마 반응으로 메탄 전환반응을 수행하였고 일반적인 플라즈마 반응에 사용되는 관형반응기 외에도 독자적인 시리즈 반응기를 설계하여 성능실험을 수행하였다. 또한 플라즈마와 촉매를 이용한 반응실험을 수행 촉매의 영향을 확인하였다. 저온 플라즈마를 이용한 메탄 전환 반응의 특성을 분석한 자료는 공정의 실용화를 위한 반응기 설계 및 반응속도를 분석하기 위한 기초자료로 기대된다.