• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.8
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• pp.338-343
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• 2017

In this study, blast furnace slag powder was used in concrete to help reduce carbon dioxide emissions and to recycle industrial waste. Blast furnace slag powder is a byproduct of smelting pig iron and is obtained by rapidly cooling molten high-temperature blast furnace slag. The powder has been used as an admixture for cement and concrete because of its high reactivity. Using fine blast furnace slag powders in concrete can reduce hydration heat, suppress temperature increases, improve long-term strength, improve durability by increasing watertightness, and inhibit corrosion of reinforcing bars by limiting chloride ion penetration. However, it has not been used much due to its low compressive strength at an early age. Therefore, this study evaluates the effects of steam curing for increasing the initial strength development of concrete made using slag powder. The relationship between compressive strength, SEM observations, and XRD measurements was also investigated. The concrete made with 30% powder showed the best performance. The steam curing seems to affect the compressive strength by destroying the coating on the powder and by producing hydrates such as ettringite and Calcium-Silicate-Hydrate gel.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.334-339
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• 1996

Midloop 운전중 RHR 기능 상실사고를 모의 실험한 Bethsy 6.9d에 대해 CATHARE2 코드를 이용하여 해석하였다. 이 실험의 초기조건은 계통수위를 고온관 중간까지 낮추고, 그 윗부분은 비응축 가스로 차 있는 midloop 상태를 유지하는 것이다. 잔열은 원자로 정지 2일 후를 가정한 노심출력을 사용하였으며, 계통내 방출유로는 상부의 Upper head vent와 가압기 vent 및 고온관 1에 연결된 Letdown line과 수위지시계 방출유로가 열려 있다고 가정하였다. 또한 세 개의 loop중 증기발생기 한대만 이유 가능하고, 나머지 두 대는 이차측이 공기로 가득 차 있는 상태를 유지하였다. 이 연구의 주된 목적은 midloop 운전중 RHR 기능 상실사고에 대한 위와같은 상태에서 계통의 열수력적 현상을 실험을 통해 이해하고 코드 예측능력을 평가하는 것이다. CATHARE2 코드 계산결과 대체적으로 실험의 현상을 잘 모의하고 있으나 다음 사항에 대해서는 차이를 보이고 있다. 첫째 노심내 물의 혼합을 적절히 모의하지 못하여, 노심내 국부적 증기 발생 시점이 실험에 비해 약 250초 빨리 나타났다. 둘째 노심에서 고온관으로의 물의 유입이 많아 고온관에서 기포율이 실험에 비해 낮게 나타났다. 마지막으로 밀림관(surge line)에서 물의 유입에 의한 압력차가 실험보다 높게 나타났다.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.783-788
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• 1998

국내 프랑스 가압경수형 원전인 울진 1,2호기 캐비티의 격납건물 직접가열에 대한 특성을 분석하기 위하여 노심용융물 고압분출 실험을 수행하였다. 본 연구에서는 환형통로 면적과 파손 직경에 따라 원자로용기 압력을 변화시키면서 용융물을 저온 용융 합금물인 Wood's Metal, 증기를 질소기체로 각각 모의하여 실험을 수행하였으며, 실험 결과는 물을 용융물 상사물로 사용한 전년 실험 결과(1)와 비교.분석하였다. 실험결과, 밀도가 물보다 큰 저온 용융 합금물을 사용한 경우는 물을 사용한 실험결과보다 밀도와 용융물의 벽면 고화고착 때문에 격납건물로 방출되는 용융물 양이 적게 나타났다. 물을 상사물로 사용한 경우와 같이 노심 용융물 고압분출에는 원자로 용기 파손직경이 많은 영향을 미치고 환형통로 면적은 큰 영향을 미치지 않는 것으로 나타났다. 노심용융물 고압분출 실험에 중요한 영향을 미치는 실험 상사물의 밀도와 용융물의 벽면 고화부착에 대해서는 종합적으로 분석하는 추가 연구가 필요하다.

• Clean Technology
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• v.22 no.4
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• pp.225-231
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• 2016

In this study, modeling and optimization study have been performed to obtain $1,524.58kg\;h^{-1}$ of a solidified NaCl by evaporating a 21.0 wt% of NaCl aqueous solution in order to reduce the steam consumption from $3,139kg\;h^{-1}$ to $496kg\;h^{-1}$ using a two-stage evaporation and a vapor recompression processes. Aspen Plus release 8.8 at AspenTech was utilized for the modeling of two stage evaporation process and PRO/II with PROVISION release 9.4 at Schneider Electric was also used for the simulation of two-stage vapor recompression process with an inter-cooler. For the simulation of the evaporation process containing NaCl aqueous solution, Aspen Plus release 8.8 at AspenTech Inc. was utilized and for the modeling of vapor recompression process PRO/II with PROVISION release at Schneider Electric Inc. For the vapor recompression process, single stage compression and two-stage compression system was compared.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.1-6
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• 2015

Recently, lots of researches on concrete with high volume mineral admixture such as ground granulated blast furnace slag (GGBFS) have been carried out to reduce $CO_2$. It is known that the precast concrete has an advantage of high strength at early age due to steam curing, even if concrete has high replacement level of mineral admixture. However it demands the investigation of compressive strength properties according to steam curing regimens. In this study, concretes with water-binder ratio of 32, 35% and water content of 135, 150, $165kg/m^3$ were produced to investigate compressive strength properties of high volume (60% by mass) GGBFS cement concrete according to steam curing regimens. Then steam curing was implemented with the maximum temperature of 50, $60^{\circ}C$ and steaming time of 5, 6, 7 hours. From the test results, it was found that steam curing was effective to raise early strength of high volume GGBFS cement concrete, but 28 day compressive strengths of steam cured specimens were lower than those of water cured specimens. Thus, a further study would be needed for the optimum steam curing regimens to satisfy target demolded strength and specified strength for the application of high volume GGBFS cement concrete to precast concrete members.

• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.454-465
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• 2015

The goal of this study is to investigate pre-service chemistry teachers’ understanding of the boiling process of a liquid mixture. We surveyed 65 students in the chemistry program of the College of Education about the boiling point of a 50%(by mole) ethanol aqueous solution and the temperature changes during heating. We then interviewed 9 of these students. According to the survey results, the percent of the pre-service teachers who thought that the boiling point of the ethanol solution would be ‘between the boiling points of ethanol and water (78-100 ℃)’ and ‘the same as that of ethanol’ were 52.3% and 35.4%, respectively. The majority of those who stated the former explained that the boiling point of the ethanol solution increased due to the effects of attraction or blocking by water molecules. Most of those who believed the latter explained that physical properties such as the boiling point would not be changed by the addition of water. With regard to the temperature change during heating, 69.2% of the teachers thought that the temperature would increase gradually while boiling, which some thought resulted from the increasing amount of water in the solution as the ethanol boiled off. Others thought that two temperature plateaus would be observed as each component of the liquid mixture underwent phase transition at its specific boiling point. When asked about the particle model of the gas phase during the boiling and evaporation process, some students drew both ethanol and water during evaporation but only ethanol when boiling. We discussed several alternative concepts of pre-service chemistry teachers about the boiling process of liquid mixtures and ways to improve their understanding.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.569-574
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• 1997

프랑스 가압경수형 원전인 울진 1,2호기 cavity의 격납용기 직접가열에 대한 특성을 분석하기 위하여 노심 용융물 고압분출 실험 연구를 수행하였다. 울진 1,2호기 격납건물은 국내의 Westinghouse와 CE형 원전과 달리 원자로용기 하부 cavity내 수평통로에 의한 출구가 없어 원자로용기 외곽의 환형통로를 통해 cavity와 격납건물 상부 대기와 직접 연결되어 있는 특성을 가지고 있다. 본 연구에서는 환형통로 면적, 파손 직경 용융물 질량 등에 따라 원자로용기 압력을 변화시키면서 용융물을 물, 증기를 질소기체로 각각 모의하여 실험을 수행하였다. 실험결과, 노심용융물 고압분출에는 원자로용기 파손 직경이 많은 영향을 미치는 것으로 나타났고 환형통로 면적과 용융물 질량은 큰영향을 미치지 않는 것으로 나타났다. 또한 환형통로 면적의 감소는 노심용융물 고압분출시 cav의 압력을 다소 상승시키는 결과를 보여주었다. 본 실험 연구에서 노심용융물 고압분출에 많은 영향을 미치지 않는 것으로 나타난 환형통로 면적에 대해서는 종합적으로 분석하는 추가 실험 이 필요하다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.205-208
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• 2008

In numerical analysis numerical values of thermodynamic properties such as temperature, pressure, specific volume, enthalpy and entropy are required. But most of the thermodynamic properties of the steam table are determined by experiment. Therefore they are supposed to have measurement errors. In order to make noised thermodynamic properties corresponding to errors, random numbers are generated, adjusted to appropriate magnitudes and added to original thermodynamic properties. the neural networks and quadratic spline interpolation method are introduced for function approximation of these modified thermodynamic properties in the saturated water based on pressure. It was proved that the neural networks give smaller percentage error compared with quadratic spline interpolation. From this fact it was confirmed that the neural networks trace the original values of thermodynamic properties better than the quadratic interpolation method.

• Nuclear Engineering and Technology
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• v.25 no.2
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• pp.215-221
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• 1993

A required initial condition for a steam explosion to occur following core meltdown accidents of a nuclear power plant is the formation of a coarse mixture of molten fuel and water. The extent of a premixing is the measure of efficiency of steam explosion that may follow. A simple one-dimensional, transient model and the flooding criteria have been applied to evaluate the fuel/coolant mixing limit. Also, both instant breakup and dynamic breakup models for the mixing process have been separately used here and compared each other. The results indicate that fuel temperature, ambient pressure, mixing diameter, water depth, and pouring diameter are the important parameters affecting the mixing behavior.

• Journal of the Korea Institute of Building Construction
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• v.21 no.2
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• pp.97-104
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• 2021

This study aims to develop non-sintered cement that can replace the Portland cement by utilizing industrial by-products. As a suggestion, the physical properties of non-sintered cement mortar depending on the curing method were investigated with ground granulated blast furnace slag, class C fly ash, and class F fly ash. As a result of the study, it was found that the strength performance and absorption rate were improved through the heat treatment process after steam curing. It was confirmed through crystal phase analysis that the hydration was accelerated after heat treatment, and the bonding material formed a dense internal structure.