• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2170-2172
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• 1999

A low energy large aperture(LELA) pulsed electron beam generator of a cold cathode type has been developed for environmental applications, for example, waste water cleaning, flue gas cleaning, and pasteurization etc. The operational principle is based on the emission of secondary electrons from cold cathode when ions in the plasma hit the cathode, which are accelerated toward exit window by the gradient of an electric potential. We have fabricated the LELA electron beam generator with the peak energy of 200keV and beam diameter of 200mm and obtained the large aperture electron beam in air. The electron beam current density has been investigated as a function of glow discharge current, accelerating voltage and radial distribution in front of the exit window foil. The plasma density and electron temperature have been measured in order to confirm the relation with the electron beam current density. We are going to upgrade the LELA electron beam generator in the electron energy, electron beam current and stability of operation for various applications.

• 설비공학논문집
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• 제11권1호
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• pp.133-146
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• 1999

The charge operation of an ice storage system has been analyzed in this paper. The thermal characteristics of major components of the ice storage system. i.e., the refrigerator and the ice storage tank are evaluated from performance tests on an existing ice storage system. Based on the measured data for thermal characteristics, a simulation is carried out for the charge operation and the effect of the refrigerator size on the system performance is investigated. The results indicate that the larger the refrigerator size for a given storage capacity, the lower the inlet temperature of the ice storage tank so that the lower the efficiency of charge operation. It is also found that there exists an optimal size of the refrigerator with which the ice storage at the end of the charge operation is maximized, but the complete charge is not possible even with the optimally sized refrigerator. This leads to the result that the design capacity of the storage tank should be larger than the required amount of cold energy for the daytime cooling considering the practically chargeable amount of cold energy during the nighttime. Where the cooling load sharing of the storage is 40%, the nominal capacity of an ice storage tank needs to be larger than the required storage amount by 30%.

• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1263-1274
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• 2009

Several experimental tests to simulate a reflood phase of a cold-leg LBLOCA of the APR1400 have been performed using the ATLAS facility. This paper describes the related experimental results with respect to the thermal-hydraulic behavior in the core and the system-core interactions during the reflood phase of the cold-leg LBLOCA conditions. The present descriptions will be focused on the LB-CL-09, LB-CL-11, LB-CL-14, and LB-CL-15 tests performed using the ATLAS. The LB-CL-09 is an integral effect test with conservative boundary condition; the LB-CL-11 and -14 are integral effect tests with realistic boundary conditions, and the LB-CL-15 is a separated effect test. The objectives of these tests are to investigate the thermal-hydraulic behavior during an entire reflood phase and to provide reliable experimental data for validating the LBLOCA analysis methodology for the APR1400. The initial and boundary conditions were obtained by applying scaling ratios to the MARS simulation results for the LBLOCA scenario of the APR1400. The ECC water flow rate from the safety injection tanks and the decay heat were simulated from the start of the reflood phase. The simulated core power was controlled to be 1.2 times that of the ANS-73 decay heat curve for LB-CL-09 and 1.02 times that of the ANS-79 decay curve for LB-CL-11, -14, and -15. The simulated ECC water flow rate from the high pressure safety injection pump was 0.32 kg/s. The present experimental data showed that the cladding temperature behavior is closely related to the collapsed water level in the core and the downcomer.

• 한국수소및신에너지학회논문집
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• 제23권4호
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• pp.382-389
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• 2012

Power generation cycle using ammonia-water mixture as working fluid has attracted much attention because of its ability to efficiently convert low-temperature heat source into useful work. If an ammonia-water power cycle is combined with a power cycle using liquefied natural gas (LNG), the conversion efficiency could be further improved owing to the cold energy of LNG at $-162^{\circ}C$. In this work parametric study is carried out on the thermodynamic performance of a power cycle consisted of an ammonia-water Rankine cycle as an upper cycle and a LNG cycle as a bottom cycle. As a driving energy the combined cycle utilizes a low-temperature heat source in the form of sensible heat. The effects on the system performance of the system parameters such as ammonia concentration ($x_b$), turbine 1 inlet pressure ($P_{H_1}$) and temperature ($T_{H_1}$), and condenser outlet temperature ($T_{L_1}$) are extensively investigated. Calculation results show that thermal efficiency increases with the increase of $P_{H_1}$, $T_{H_1}$ and the decrease of $T_{L_1}$, while its dependence on $x_b$ has a downward convex shape. The changes of net work generation with respect to $P_{H_1}$, $T_{H_1}$, $T_{L_1}$, and $x_b$ are roughly linear.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1206-1212
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• 2022

Cold-crucible induction melting (CCIM) technology has been intensively studied as an advanced vitrification process for the immobilization of highly radioactive waste. This technology uses high-frequency induction to melt a glass matrix and waste, while the outer surface of the crucible is water-cooled, resulting in the formation of a frozen glass layer (skull). In this study, for the fabrication of borosilicate glass waste form, CCIM operation test with 60 kg of glass per batch was conducted using surrogate wastes composed of Cs, Sr, and Nd as a representative of highly radioactive nuclides generated during spent nuclear fuel management. A 60 kg-scale glass waste form was successfully fabricated through melting and draining processes using a CCIM system, and its physicochemical properties were analyzed. In particular, to enhance the controllability and reliability of the draining process, an air-cooling drain control method that can control draining through air-cooling near drain holes was developed, and its validity for draining control was verified. The method can offer controllability on various draining processes, such as molten salt or molten metal draining processes, and can be applied to a process requiring high throughput draining.

• Nuclear Engineering and Technology
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• 제41권4호
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• pp.521-530
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• 2009

Neutron science and technology, the utilization of neutron beams for a wide variety of scientific and engineering research ranging from materials and life science to industrial applications, has been one of the key elements of modem science and technology. Currently, the neutron science and technology in Korea is in rapid growth with the operation of the 30 MW High-flux Advanced Neutron Application Reactor (HANARO) at the Korea Atomic Energy Research Institute, which is one of the most powerful nuclear research reactors in the world. Furthermore, a state of the art HANARO cold neutron research facility, which will open a new era for the neutron science and technology in Korea, is expected to become available in 2010. In this paper, the progress of neutron science and technology in Korea is reviewed and its unprecedented new opportunities and challenges in coming years are presented.

• 한국수소및신에너지학회논문집
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• 제20권3호
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• pp.224-231
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• 2009

The improvement of cold start capability is one of the most challenging tasks to be solved for commercialization of fuel cell vehicle. In this study, cold start test and ice blocking test(IBT) of fuel cell stack were carried out under various operating conditions. This fuel cell stack can be thawed from -20$^{\circ}$C within 25s and the voltage change was found to be comprised of 4 steps; the first step is the voltage decrease by overpotential, the second step is the voltage increase by the cell temperature increase, the third step is the voltage decrease by ice blocking, and the last step is the voltage increase by thawing. Bootstrap startup was failed after shutdown at temperature under 40$^{\circ}$C because of much condensed water in the fuel cell. Quantitative estimation of cold start capability have been demonstrated by ice blocking test(IBT). In the results, it was found that cold start capability was improved double every 10$^{\circ}$C from 30$^{\circ}$C to 65$^{\circ}$C and enhanced by 30% at the condition of SR 3/4 compared to SR 1.5/2.0 and enhanced by 20% with dry purge condition compared to with RH 50% purge condition.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.859-867
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• 2011

The cold start problem is one of major obstacles to overcome for the commercialization of fuel cell vehicles. However, the cold start characteristics of fuel cell systems are very complicated since various phenomena, i.e. ice-blocking, electro-chemical reactions, heat transfer, and defrosting of BOP components, are involved in them. This paper presents a framework to approach the problem at a full stack scale using Axiomatic Design (AD). It was characterized in terms of Functional Requirements (FRs) and Design Parameters (DPs) while their relations were established in a design matrix. Considering the design matrix, the endplates should have low thermal conductivity and capacity without increase in weight or decrease in structural stiffness. Consequently, composite sandwich endplates were proposed and examined both through finite element analyses and experiments simulating cold start conditions. From the examinations, it was found that the composite sandwich endplates significantly contributed to improving the cold start characteristics of PEMFC.

• 한국재료학회지
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• 제29권5호
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• pp.336-341
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• 2019

The gas adsorption isotherm requires accurate measurement for the analysis of porous materials and is used as an index of surface area, pore distribution, and adsorption amount of gas. Basically, adsorption isotherms of porous materials are measured conventionally at 77K and 87K using liquid nitrogen and liquid argon. The cold volume calibration in this conventional method is done simply by splitting a sample cell into two zones (cold and warm volumes) by controlling the level sensor in a Dewar filled with liquid nitrogen or argon. As a result, BET measurement for textural properties is mainly limited to liquefied gases (i.e. $N_2$ or Ar) at atmospheric pressure. In order to independently investigate other gases (e.g. hydrogen isotopes) at cryogenic temperature, a novel temperature control system in the sample cell is required, and consequently cold volume calibration at various temperatures becomes more important. In this study, a cryocooler system is installed in a commercially available BET device to control the sample cell temperature, and the automated cold volume calibration method of temperature variation is introduced. This developed calibration method presents a reliable and reproducible method of cryogenic measurement for hydrogen isotope separation in porous materials, and also provides large flexibility for evaluating various other gases at various temperature.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 하계학술발표대회
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• pp.32-32
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• 2005