• 방사성폐기물학회지
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• 제7권4호
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• pp.229-236
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• 2009

우리나라에서 발생하는 사용후핵 연료를 CANDU형과 PWR형 2종류로 구분한다. PWR형 사용후핵 연료의 경우 적절한 공정을 거쳐 원료물질로 다시 사용할 수 있는 물질을 많이 포함하고 있어 재활용 공정을 고려할 수 있다. CANDU형 사용후핵 연료는 천연 우라늄을 원료물질로 사용하고 있어 재활용 가능성이 거의 없으므로 직접 처분을 고려하고 있다. 본 논문에서는 PWR형과 CANDU형 사용후핵연료 모두를 직접 처분하는 개념으로 개발한 한국형 사용후핵연료 처분시스템을 바탕으로 CANDU형 사용후핵연료 처분 시스템을 향상시키는 방안을 도출하고자 하였다. 이를 위하여, 현재 원자력발전소에서 사용하고 있는 사용후핵연료 60 다발(Bundle) 용량의 저장바스켓을 포장 활용하는 방안으로 처분용기 개념을 개선하였다. 이들 개선한 처분용기를 기반으로 하여 사용후핵연료의 심지층 처분시스템에 있어서 주요한 제한요건인 폐기물로부터 발생된 열로 인하여 완충재의 온도가 $100^{\circ}C$를 넘지 않도록 하는 요건을 만족시키면서 효율을 향상시킨 처분시스템 개념을 제시하였다. 제시한 처분 시스템 개념들은 장기저장 및 회수성이 용이한 방안을 도입한 개념과 개선한 처분용기를 1개 처분공에 2단으로 처분하는 것으로서 이들 개념을 기존 한국형 처분시스템과 효율성 측면 에서 비교 분석하였다. 본 연구를 통하여 얻은 CANDU 사용후핵연료 처분개념은 단위면적당 열효율, U-density, 처분면적, 굴착량, 완충재 및 폐쇄 물질량을 30~40 %까지 효율을 향상시킬 수 있었다.

• 한국재료학회지
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• 제28권6호
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• pp.343-348
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• 2018

Recently, the properties of nanostructured materials as advanced engineering materials have received great attention. These properties include fracture toughness and a high degree of hardness. To hinder grain growth during sintering, it is necessary to fabricate nanostructured materials. In this respect, a high-frequency induction-heated sintering method has been presented as an effective technique for making nanostructured materials at a lower temperature in a very short heating period. Nanopowders of W and $Al_2O_3$ are synthesized from $WO_3$ and Al powders during high-energy ball milling. Highly dense nanostructured $W-Al_2O_3$ composites are made within three minutes by high-frequency induction-heated sintering method and materials are evaluated in terms of hardness, fracture toughness, and microstructure. The hardness and fracture toughness of the composite are $1364kg/mm^2$ and $7.1MPa{\cdot}m^{1/2}$, respectively. Fracture toughness of nanostructured $W-Al_2O_3$ is higher than that of monolithic $Al_2O_3$. The hardness of this composite is higher than that of monolithic W.

• 한국연소학회지
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• 제14권3호
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• pp.16-23
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• 2009

It is strongly desired for coal-fired power plants to utilize not only low-rank coals with high moisture contents, but also lowering cost with diversifying fuel sources. In this study, combustion characteristics of low rank coal with high moisture, and standard pulverized coals are experimentally investigated using TGA (Thermogravimetric Analysis) and DTF (drop tube furnace). The coals tested are three kinds of coal with moisture content ranging from 8.32 to 26.82%. The results show that under the air combustion condition, the burn-out time at TGA rises as moisture content increases, and standard pulverized coal with 8.32% moisture content showed the lowest activation energy of 55.73 kJ/mol. In case of the high amount of moisture, the combustion efficiency decreases due to evaporation heat loss, and unburned carbon in ash produced at combustion process in DTF increased. Aslo, initial deformation temperature of slag attached in alumina tube of DTF decreased with lowering the crytallinity of anorthite and augite. To improve the combustion reactivity and efficiency, it is effective to upgrade through drying the high moisture coal to moisture level (less than 10%) of standard pulverized coal.

• 한국세라믹학회지
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• 제51권4호
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• pp.283-288
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• 2014

PdO-doped $BaZr_{0.85}Y_{0.15}O_{3-\delta}$ (BZPY) proton conductors have been proposed as applicable for intermediate temperature electrolytes for protonic ceramic fuel cells (PCFCs) because the PdO doping is effective for improving the proton conductivity of $BaZr_{0.85}Y_{0.15}O_{3-\delta}$ (BZY) with high affinity for hydrogen. In order to further improve the conductivity of BZPY, two-phase composite electrolytes consisting of a BZPY and molten carbonate were designed. Dense BZPY-based composite electrolytes were fabricated after sintering at $670^{\circ}C$ for 4 h, since molten carbonates fill the grain boundary of the porous BZPY matrix. Furthermore, BZPY/$(Li-0.5Na)_2CO_3$ composites show a significantly enhanced protonic conductivity at intermediate temperatures. This may be because easy proton transport is possible through the interface of the carbonate and oxide phase.

• Nuclear Engineering and Technology
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• 제49권4호
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• pp.700-709
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• 2017

This work looks at the effect of changes in kinetic parameters on simultaneous reactivity insertions and beam tube flooding in a typical material testing reactor-type research reactor with low enriched high density ($U_3Si_2-Al$) fuel. Using a modified PARET code, various ramp reactivity insertions (from $0.1/0.5 s to $1.3/0.5 s) plus beam tube flooding ($0.5/0.25 s) accidents under uncontrolled conditions were analyzed to find their effects on peak power, net reactivity, and temperature. Then, the effects of changes in kinetic parameters including the Doppler coefficient, prompt neutron lifetime, and delayed neutron fractions on simultaneous reactivity insertion and beam tube flooding accidents were analyzed. Results show that the power peak values are significantly sensitive to the Doppler coefficient of the system in coupled accidents. The material testing reactor-type system under such a coupled accident is not very sensitive to changes in the prompt neutron life time; the core under such a coupled transient is not very sensitive to changes in the effective delayed neutron fraction.

• 한국수소및신에너지학회논문집
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• 제14권2호
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• pp.138-145
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• 2003

There are high expectations for DME(Dimethyl Ether) as a new alternative fuel for diesel engine. Compared with the conventional diesel engine, nearly zero soot emission and high thermal efficiency have been reported from DME fuelled CI engines. However, higher NOx emission is one of the disadvantages from DME Engines. In the present study, cooled EGR(Exhaust Gas Recirculation) was applied to DME engine modified from conventional Dl diesel engine, and effects of EGR were examined under various EGR temperature. Finally, it was concluded that the cooled EGR is an effective solution to reduce NOx emission from DME engine.

• 전기화학회지
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• 제2권4호
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• pp.190-194
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• 1999

고분자전해질형 연료전지에서 에칭한 Nafion막으로 고분자막/전극 어셈블리를 제조하고 그 성능을 측정하였다. 에칭을 함으로서 고분자막과 전극의 접합이 잘 이루어져 hot pressing 압력과 온도를 낮출 수 있었고, 낮은 온도에서 hot pressing이 이루어짐으로서 전지의 성능을 향상시킬 수 있었다. 어셈블리 제조방법중의 하나인 페인팅 방법에서 에칭 된 Nafion막을 이용하면 전지의 성능이 향상됨을 보였으며, 에칭정도에 따라 적당한 양의 전극촉매를 사용해야 함을 보였다.

• 한국전기전자재료학회논문지
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• 제33권4호
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• pp.310-314
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• 2020

Although waste oil derived fuel (WDF) production technology was developed under a government initiative ~10 years ago, it became stagnant owing to the small size of participating companies, residents' rejection of foul odor, and the nature of the technology for recycling waste that was avoided. However, this subject is under the spotlight again because of recent developments, such as garbage crisis. In particular, plastic is the most difficult waste to dispose of, with more than 4 million tons of plastic waste produced every year according to statistics from the Ministry of Environment. The most effective method for treating plastic waste is to produce WDF through low temperature thermal decomposition. The WDF includes several volatile ingredients that mostly limit the use of fuel for boilers, owing to safety concerns. In particular, flash point is legally stipulated because of secondary contamination in the distribution process and the risk of fire and explosion. It is required that external shipments (distribution) should be maintained in the range of at least 30~60℃ (excluding explosion prevention facilities) for diesel power generation. Therefore, this study seeks to find the flash point that is best suited to WDFs produced from plastic waste.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.133-136
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• 2008

본 연구는 추진제를 공급하는 터보펌프와 연계한 연료 과농 가스발생기의 연소 특성에 관한 것이다. 총 5회의 연소시험이 안정적으로 실시되었다. 가스발생기의 압력 형성은 터보펌프로부터 추진제 공급유량에 따라 연동하였다. 터보펌프를 가스발생기 가스로 직접 구동하는 폐회로 시험에서도 안정적인 작동 성능을 보여주었다. 연소 가스의 온도 형성은 이전 시험 결과와 비슷한 양상을 보였다. 실제 작동 연소 압력 변경을 위해 장착한 오리피스는 압력 섭동 저감에 효과적이었으나 45 bar 이하의 저압에서는 단품 시험 시와 동일한 압력 섭동 특성을 보여주었다.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.764-769
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• 2022

The United Arab Emirates is currently building and operating four units of the APR-1400 developed by a South Korean vendor, Korea Electric Power Corporation (KEPCO). This paper attempts to perform APR-1400 reactor core analysis by using the well-known two-step method. The two-step method was applied to the APR-1400 first cycle using the open-source nodal diffusion code, KOMODO. In this study, the group constants were generated using CASMO-4 fuel transport lattice code. The simulation was performed in Hot Zero Power (HZP) at steady-state and transient conditions. Some typical parameters necessary for the Nuclear Design Report (NDR) were evaluated in this paper, such as effective neutron multiplication factor, control rod worth, and critical boron concentration for steady-state analysis. Other parameters such as reactivity insertion, power, and fuel temperature changes during the Reactivity Insertion Accident (RIA) simulation were evaluated as well. The results from KOMODO were verified using PARCS and SIMULATE-3 nodal core simulators. It was found that KOMODO gives an excellent agreement.