• Nuclear Engineering and Technology
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• v.44 no.3
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• pp.237-248
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• 2012

Corium behavior in the lower plenum of the reactor vessel during a severe accident is very important, as this affects a failure mechanism of the lower head vessel and a thermal load to the outer reactor vessel under the IVR-ERVC (In-Vessel corium Retention through External Reactor Vessel Cooling) condition. This paper discusses the state of the art and technical issues on corium behavior in the lower plenum, such as initial corium pool formation characteristics and its transient behavior, natural convection heat transfer in various geometries, natural convection heat transfer with a phase change of melting and solidification, and corium interaction with a lower head vessel including penetrations of the ICI (In-Core Instrumentation) nozzle are discussed. It is recommended that more detailed analysis and experiments are necessary to solve the uncertainties of corium behavior in the lower plenum of the reactor vessel.

• Journal of Korea Multimedia Society
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• v.7 no.12
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• pp.1657-1664
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• 2004

We propose a method that classifies images into two object types man-made and natural objects. A central object is extracted from each image by using central object extraction method[1] before classification. A central object in an images defined as a set of regions that lies around center of the image and has significant color distribution against its surrounding. We define three measures to classify the object images. The first measure is energy of edge direction histogram. The energy is calculated based on the direction of only non-circular edges. The second measure is an energy difference along directions in Gabor filter dictionary. Maximum and minimum energy along directions in Gabor filter dictionary are selected and the energy difference is computed as the ratio of the maximum to the minimum value. The last one is a shape of an object, which is also represented by Gabor filter dictionary. Gabor filter dictionary for the shape of an object differs from the one for the texture in an object in which the former is computed from a binarized object image. Each measure is combined by using majority rule tin which decisions are made by the majority. A test with 600 images shows a classification accuracy of 86%.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.4
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• pp.363-369
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• 2018

This paper considers the alternative way to mitigate cost for REC instead of Photovoltaic (PV) panels with Energy Storage System (ESS). This study starts from an economic analysis of a 1 megawatt PV system without ESS. Several assumptions have been applied in consideration of the current domestic situation. Based on this result, the economic efficiency of PV with ESS improved. However, the reliance on government subsidies was very high. The alternative way to cover the fluctuation power from renewable energy was reviewed with economical and technical way. In case the natural gas engine applied to PV, the IRR and Levelized Cost of Electricity (LCOE) can be improved without ESS. And if small amount of additional REC, the IRR can be improved up to investment level.

• Journal of Radiation Protection and Research
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• v.26 no.3
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• pp.299-303
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• 2001

Using ultrasound techniques, the Korea Atomic Energy Research Institute has measured chest wall thicknesses of a group of male workers at the Korea Atomic Energy Research Institute. A site-specific biometric equation has been developed for these workers. Chest wall thickness is an important modifier on lung counting efficiency. These data have been put into the perspective of the ICRP recommended dose limits for occupationally exposed workers: 100 mSv in a 5-year period with a maximum of 50 mSv in anyone year. For measured chest wall thicknesses of 1.9 cm to 4.1 cm and a 30 min counting time, the achievable MDAs for natural uranium in the KAERI lung counter vary from 5.75 mg to 11.28 mg. These values are close to, or even exceed, the predicted amounts of natural uranium that will remain in the lung (absorption type M and S) after an intake equal to the Annual Limit on Intake corresponding to a committed dose of 20 mSv. This paper shows that the KAERI lung counter probably cannot detect an intake of Type S natural uranium in a worker with a chest wall thickness equal to the average value (2.7 cm) under routine counting conditions.

• Journal of the Korean Solar Energy Society
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• v.31 no.6
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• pp.40-48
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• 2011

과냉 촉진을 위한 새로운 열교환기(HESC)가 생활공간의 냉난방을 위한 공기-물 열펌프의 성능계수 향상을 위해 본 연구에서 개발되었으며 그 효과를 실험적으로 분석하였다. 이 열교환기(HESC)는 여러 단계의 셀과 튜브로 구성되어 있으며, 열펌프 시스템의 응축기와 증발기 사이에 장착되었다. 실험 조건으로, 외기온은 $7^{\circ}C$에서 $-17^{\circ}C$, 입구 물 온도는 $7{\sim}10^{\circ}C$ 그리고 제 2열전달매체로서 물의 질량 유동율은 시간당 100에서 $300{\ell}$로 변화를 주었다. 본 실험에서 이 열교환기가 장착된 열펌프의 압축기에서의 냉매 입 출구 사이의 온도 차이는 열교환기가 장착되지 않은 열펌프보다 $15^{\circ}C$ 높았다. 이에 따라 이 열교환기가 장착된 열펌프 시스템은 외기온 $-10^{\circ}C$에서 COP가 0.8 증가하였다. 따라서 이 공기-물 열펌프 시스템은 최근 한국에서 실용화되고 있는 고비용이 요구되는 지열 열펌프 시스템을 대체하여 생활공간을 위한 냉난방 시스템으로서 중요한 역할을 할 수 있을 것으로 사료된다.

• Journal of the Korean Institute of Gas
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• v.15 no.6
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• pp.38-43
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• 2011

Natural gas liquefaction process runs under cryogenic condition, and it spends large amount of energy. Minimizing energy consumption of natural gas liquefaction process is an important issue because of its physical characteristics. Among many kinds of natural gas liquefaction processes, C3-MR(Propane Pre-cooled Mixed Refrigerant) process uses two kind of refrigerants. One is the propane as the pure refrigerant(PR) and the other is the mixed refrigerant(MR). In this study, to find the optimal compressing level, propane cycle is simulated on different pressure level. The case study result shows relationship between energy consumption and pressure level. As a result, the conclusion is that at a higher pressure level, process consumes lower energy. At 5 pressure-levels, energy consumption is 23.7% lower than 3 pressure-levels.

• Journal of the Korean Institute of Gas
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• v.23 no.1
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• pp.36-40
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• 2019

In this study, we compared the operational rates of natural gas, coal, nuclear power and renewable energy based on the data of power generation and power generation facilities produced in summer season(from June to August) during the last four years(2015~2018). Nuclear power and coal power, which are responsible for basic power generation, were guaranteed to be economical as the actual generation capacity remained 60% higher than the cost of power generation. On the other hand, natural gas generation and new renewable energy generation have a very low actual operation rate of 29.5% and 27.3% compared to investments in power generation facilities, making it difficult to lower the cost of power generation. However, coal generation has structural problems in terms of greenhouse gas, fine dust. On the other hand, natural gas generation is relatively low and even though it is safe, it is difficult to secure economic feasibility as it is bound by a peak power system. Therefore, it is only possible to achieve balanced development of energy sources when there is a change in the development policy.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2997-3009
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• 2023

The Passive containment Air-cooling System (PAS) can effectively remove the decay heat of the modular small nuclear reactor after an accident. The details of natural convection around the dome, which is a key part of PAS, were investigated numerically in the present study. The thermal dynamics around the dome were studied through the temperature, pressure and velocity contours and the streamlines. Additionally, the formation of the buoyant plume at the top of the dome was investigated. The results show that with the increase of Ra, the lift-off point moves toward the bottom of the dome, and the eddy under the buoyant plume grows larger gradually, which enhances the heat transfer. And the heat transfer along the dome surface with different truncation angles was investigated. As the angle increases, the heat transfer coefficient becomes stronger as well. Consequently, a newly developed heat transfer correlation considering the influence of truncation angle for the dome is proposed based on the simulated results. This study could provide a better understanding of natural convection around the dome of PAS and the proposed correlation could also offer more predictive value in the improvement of nuclear safety.

• Journal of Energy Engineering
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• v.20 no.4
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• pp.318-329
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• 2011

This study focuses on enhancing the accuracy of consumption function of Korean natural gas for city gas. It is using time-series model with time-varying coefficients taking into account the recent abnormal temperature phenomenon and the changing gross domestic product (GDP) as important variables. This study estimates the cointegrating regression model for the long-run estimation and the error correction model for the short-run estimation. The consumption function of Korean natural gas is estimated to be influenced by the time-varying coefficients of GDP and temperature. Using the estimated time-series model with time-varying coefficients, this study forecasts the consumption of natural gas for city gas from July 2011 to December 2012. The consumption in 2011 would be 18,303 thousand tons, which is little different from the imported 18,681 thousand tons. The consumption of natural gas for city gas in 2012 is forecast to be 19,213 thousand tons. The consumption model of this study is needed to extend by considering the relative prices between natural gas and its substitutes, the scale of consumers and others.

• Proceedings of the Korean Nuclear Society Conference
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• 2003.10a
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• pp.67.1-67.1
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• 2003