• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.6
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• pp.36-43
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• 1997

To cope with quest to improve the fuel economy and vehicle performance, Continuously Variable Transmission with Changing the speed ratio between minimum and maximum ratio by infinite step, is more efficient than conventional multi-ratio transmission. In this paper, to investigate a specific CVT shift ratio diagram and CVT shift characteristics, CVT vehicle was tested on the proving ground and chassis dynamometer. The test results are as follows; CVT can obtain the excellent vehicle performance and fuel economy changing the shift ratio by infinite step, without rapid change of engine revolution and driving force. And CVT can set up a special shift range that obtains not only the engine brake effect but also the maximum speed driving.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.573-581
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• 1999

액체 금속로(LMIR) 핵연료교환장치의 기본설계를 위해서는 여러 분야(예를 들면, 기구학, 동역 학, 재료역학 등)의 해석을 동시에 수행해야 한다. 그러나 이와 같은 해석들은 각각 별개로 연속적으로 수행되는 것이 아니라, 상호 유기적인 연관을 갖고 수행되어야 한다. 이와 같은 해석에 적합한 기법이 MDO 기법이다. 본 논문에서는 MDO기법에 의한 핵연료교환장치 구조해석의 한 단계로 핵연료교환장치의 기구 동역 학 해석을 수행하여 핵연료 교환장치 작동에 대한 기구운동학적 특성 및 동역학적 특성을 분석하였다. 분석결과 해석대상 핵연료교환장치는 예상한대로 원활하게 작동됨이 확인되었다. 아울러 이 분석 결과를 토대로 핵연료교환장치의 정적 휨 변형을 구하기 위한 재료역학해석에서 요구되는 정적구조를 결정하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.583-589
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• 1999

본 논문에서는 MDO기법에 의한 핵연료교환장치의 구조해석 단계 중 핵연료교환장치의 휨 변형을 구하는 재료역학해석을 수행하였다. 이는 액체 금속로(LMR) 핵연료교환장치의 기본설계를 위하여 매우 중요하다. 해석대상 핵연료교환장치의 정적구조는 기 수행한 핵연료교환장치의 기구 동역 학 해석 결과를 활용하였다. 네 가지 핵연료교환동작에 대하여 핵연료 봉의 무게를 100㎏에서 500㎏까지 100㎏씩 증가시켜 휨 변형의 크기를 구하였다. 그 결과 회전 중심 축에서 가장 멀리 있는 핵연료 봉을 교환하는 핵연료교환동작에서 최대 휨 변형이 발생함이 밝혀졌다. 또한 이 최대 휨 변형이 발생하는 핵연료교환장치구조에 대하여 부재의 단면두께를 축소하면서, 또 단면형상을 여러 가지로 바꾸면서 휨 변형크기를 구하여 비교하였다. 비교결과 비교대상 단면형상 중에서 중공직사각형 단면이 최소 휨 변형이 발생하는 최적단면형상임이 밝혀졌다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.2
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• pp.255-266
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• 2021

Solid-state mechanochemical reduction combined with subsequent melting consolidation was suggested as a technical option for the oxide reduction in pyroprocessing. Ni ingot was produced from NiO as a starting material through this technique while Li metal was used as a reducing agent. To determine the technical feasibility of this approach for pyroprocessing, which handles spent nuclear fuels, thermodynamic calculations of the phase stabilities of various metal oxides of U and other fission elements were made when several alkaline and alkali-earth metals were used as reducing agents. This technique is expected to be beneficial, not only for oxide reduction but also for other unit processes involved in pyroprocessing.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.4
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• pp.329-333
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• 2005

To identify the effect of engineered barriers on the leach rate of cesium from spent PWR fuel under a synthetic granitic groundwater, the related leach tests with and without bentonite or metals have been performed up to about 6 years. The leach rates were decreased as a function of leaching time and then became a constant after a certain period. The period in a bare spent fuel was much longer than that with bentonite or metal sheets. The cumulative fraction of cesium released from the spent fuel with bentonite or with copper and stainless steel sheets was steadily increased, but the fraction from bare fuel was rapidly and then sluggishly increased. However, the values deducted its gap inventory from the cumulative fraction of cesium released from the bare fuel was almost very close to the others. These suggest that the initial release of cesium from bare fuel might be dependant on its gap inventory and the effect of engineered barriers on the long-term leach rate of cesium would be insignificant but the rate with engineered barriers could be reduced in the initial transient period due to their retardation effect. And the long-term leach rate of cesium from spent fuel in a repository would be approached to a constant rate of $2\times10^{-2}g/m^2-day$.

• Journal of Environmental Science International
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• v.19 no.12
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• pp.1355-1359
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• 2010

The application of metal caps has been continuously increased as real life are extended. Metal caps is usually made of aluminum and polyethylene(PE) as packing. Since metal caps contain 75% aluminum on a weight basis, metal caps may be a valuable source when these were properly recovered. The recovery methods of metal caps have mechanical peeling and incineration. However these are either hard to apply in some case or environmentally unacceptable. So in this investigation, recovery method of aluminum from metal caps was investigated using pyrolysis. The result shows that pyrolysis temperature and pyrolysis time was $450^{\circ}C$ and 120min. respectively. Also 100% of aluminum was recovered from metal caps. Heat content of recovered oil was high enough to use as a fuel representing 7,425.0, 7,793.1, 7,583.2, 7,726.2(cal/g). Heavy metal contens in the oil were under regulatory limit indicating.

• Nuclear Engineering and Technology
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• v.53 no.11
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• pp.3563-3579
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• 2021

Measured decay heat data of light water reactor (LWR) spent nuclear fuel (SNF) assemblies are adopted to train machine learning (ML) models. The measured data is available for fuel assemblies irradiated in commercial reactors operated in the United States and Sweden. The data comes from calorimetric measurements of discharged pressurized water reactor (PWR) and boiling water reactor (BWR) fuel assemblies. 91 and 171 measurements of PWR and BWR assembly decay heat data are used, respectively. Due to the small size of the measurement dataset, we propose: (i) to use the method of multiple runs (ii) to generate and use synthetic data, as large dataset which has similar statistical characteristics as the original dataset. Three ML models are developed based on Gaussian process (GP), support vector machines (SVM) and neural networks (NN), with four inputs including the fuel assembly averaged enrichment, assembly averaged burnup, initial heavy metal mass, and cooling time after discharge. The outcomes of this work are (i) development of ML models which predict LWR fuel assembly decay heat from the four inputs (ii) generation and application of synthetic data which improves the performance of the ML models (iii) uncertainty analysis of the ML models and their predictions.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4084-4094
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• 2022

The Advanced Fuels Campaign Fission Accelerated Steady-state Test (FAST) at Idaho National Laboratory (INL) completed its first irradiation cycle within the Advanced Test Reactor (ATR). The test focused on the irradiation of alloy fuel forms for use in sodium fast reactors. The first cycle of FAST testing was completed and four rodlets were removed for the initial post irradiation examination (PIE). The rodlet design and irradiation conditions were evaluated using Monte Carlo N-Particle (MCNP) for as-run power history and COMSOL for temperature analysis. These rodlets include a set of low burnups (~2.5 % fissions per initial metal atoms [%FIMA]), control rodlets, and a helium-bonded annular rodlet (4.7 %FIMA). Nondestructive PIE has been completed and includes visual inspection, neutron radiography and gamma scanning of the FAST capsules and rodlets. Radiography confirmed the integrity of the experiments, revealed that the annulus in the annular fuel was filled at a modest burnup (4.7 %FIMA), and indicated potential slumping of the cooler rodlets at lower burnup. Precision gamma scanning indicated mostly usual fission product behavior, except for cesium in the He-bonded annular fuel. Future destructive PIE will be necessary to fully interpret the effects of accelerated irradiation on U-Zr metallic fuel behavior.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.3
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• pp.1-10
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• 1998

In this paper, we investigated the improvement of characteristics of knock, emission and fuel consumption rate by optimizing the location and size of water transfer holes in cylinder head gasket without change of engine water jacket design itself. The cooling system was modified in the direction of reducing the metal temperature in the head and increasing the metal temperature in the block. The optimization of water transfer holes in cylinder head gasket was obtained by "flow visualization test". The water transfer holes were concentrated in front side of the engine in order to reduce thermal boundary layer in the water jacket of No. 2 and No. 3 combustion changer in the cylinder head, which would have a large knock intensity, and increase thermal boundary layer in the water jacket of the cylinder block. When the modified coolant flow pattern was applied as proposed in this paper, the knock characteristic was improved. The spark timing was advanced up to 2$^{\circ}$ in low and middle speed range at a full load. In addition, HC emission at MBT was reduced by 5.2%, and the fuel consumption rate was decreased up to 1% in the driving condition of 2400 rpm and 250 KPa. However, since this coolant flow pattern mentioned in this paper might deteriorate the performance of vehicle cooling system due to the coolant flow rate reduction, a properly optimized point should be obtained. obtained.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.133-133
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• 2013

For both oxygen reduction (ORR) and hydrogen oxidation reactions (HOR) of proton electrolyte membrane fuel cells (PEMFCs), alloying Pt with another transition metal usually results in a higher activity relative to pure Pt, mainly due to electronic modification of Pt and bifunctional behaviour of alloy surface for ORR and HOR, respectively. However, activity and stability are closely related to the preparation of alloy nanoparticles. Preparation conditions of alloy nanoparticles have strong influence on surface composition, oxidation state, nanoparticle size, shape, and contamination, which result from a large difference in redox priority of metal precursors, intrinsic properties of metals, increasedreactivity of nanocrystallites, and interactions with constituents for the synthesis such as solvent, stabilizer, and reducing agent, etc. Carbon-supported Pt-Ni alloy nanoparticles were prepared by the borohydride reduction method in anhydrous solvent. Pt-Ru alloy nanoparticles supported on carbon black were also prepared by the similar synthetic method to that of Pt-Ni. Since electrocatalytic reactions are strongly dependent on the surface structure of metal catalysts, the atom-leveled design of the surface structure plays a significant role in a high catalytic activity and the utilization of electrocatalysts. Therefore, surface-modified electrocatalysts have attracted much attention due to their unique structure and new electronic and electrocatalytic properties. The carbon-supported Au and Pd nanoparticles were adapted as the substrate and the successive reduction process was used for depositing Pt and PtM (M=Ru, Pd, and Rh) bimetallic elements on the surface of Au and Pd nanoparticles. Distinct features of the overlayers for electrocatalytic activities including methanol oxidation, formic acid oxidation, and oxygen reduction were investigated.