• Nuclear Engineering and Technology
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• 제47권6호
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• pp.678-699
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• 2015

Although the harsh space environment imposes many severe challenges to space pioneers, space exploration is a realistic and profitable goal for long-term humanity survival. One of the viable and promising options to overcome the harsh environment of space is nuclear propulsion. Particularly, the Nuclear Thermal Rocket (NTR) is a leading candidate for nearterm human missions to Mars and beyond due to its relatively high thrust and efficiency. Traditional NTR designs use typically high power reactors with fast or epithermal neutron spectrums to simplify core design and to maximize thrust. In parallel there are a series of new NTR designs with lower thrust and higher efficiency, designed to enhance mission versatility and safety through the use of redundant engines (when used in a clustered engine arrangement) for future commercialization. This paper proposes a new NTR design of the second design philosophy, Korea Advanced NUclear Thermal Engine Rocket (KANUTER), for future space applications. The KANUTER consists of an Extremely High Temperature Gas cooled Reactor (EHTGR) utilizing hydrogen propellant, a propulsion system, and an optional electricity generation system to provide propulsion as well as electricity generation. The innovatively small engine has the characteristics of high efficiency, being compact and lightweight, and bimodal capability. The notable characteristics result from the moderated EHTGR design, uniquely utilizing the integrated fuel element with an ultra heat-resistant carbide fuel, an efficient metal hydride moderator, protectively cooling channels and an individual pressure tube in an all-in-one package. The EHTGR can be bimodally operated in a propulsion mode of $100MW_{th}$ and an electricity generation mode of $100MW_{th}$, equipped with a dynamic energy conversion system. To investigate the design features of the new reactor and to estimate referential engine performance, a preliminary design study in terms of neutronics and thermohydraulics was carried out. The result indicates that the innovative design has great potential for high propellant efficiency and thrust-to-weight of engine ratio, compared with the existing NTR designs. However, the build-up of fission products in fuel has a significant impact on the bimodal operation of the moderated reactor such as xenon-induced dead time. This issue can be overcome by building in excess reactivity and control margin for the reactor design.

• 천문학논총
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• 제32권1호
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• pp.359-361
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• 2017

We report our research on aluminum mirror optics for future infrared astronomical satellites. For space infrared missions, cooling the whole instrument is crucial to suppress the infrared background and detector noise. In this aspect, aluminum is appropriate for cryogenic optics, because the same material can be used for the whole structure of the instrument including optical components thanks to its excellent machinability, which helps to mitigate optical misalignment at low temperatures. We have fabricated aluminum mirrors with ultra-precision machining and measured the wave front errors (WFEs) of the mirrors with a Fizeau interferometer. Based on the power spectral densities of the WFEs, we confirmed that the surface accuracy of all the mirrors satisfied the requirements for the SPICA Coronagraph Instrument. We then integrated the mirrors into an optical system, and examined the image quality of the system with an optical laser. As a result, the total WFE is estimated to be 33 nm (rms) from the Strehl ratio. This is consistent with the WFEs estimated from the measurement of the individual mirrors.

• 지식경영연구
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• 제17권2호
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• pp.27-50
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• 2016

Korean manufacturing industry have recently faced the catch-up of China in the mass commodity product, such as automotive, display, and smart phone in terms of market as well as technology. Accordingly, discussion on the importance of achieving catch-up in complex product systems (CoPS) has been increasing as a new innovation engine for the industry. In order to achieve successful catch-up of CoPS, we explored emerging technologies of CoPS, which are featured by the characteristics of radical novelty, relatively fast growth and self-sustaining, through the study of emerging technologies of gas turbine for power generation. We found that emerging technologies of the gas turbine are technologies for combustion nozzle and composition of electrical machine for increasing power efficiency, washing technology for particulate matter, cast and material processing technology for enhancing durability from fatigue, cooling technologies from extremely high temperature, interconnection operation technology between renewable energy and the gas turbine for flexibility in power generation, and big data technology for remote monitoring and diagnosis of the gas turbine. We also found that those emerging technologies resulted in technological progress of the gas turbine by converging with other conventional technologies in the gas turbine. It indicates that emerging technologies in CoPS can be appeared on various technological knowledge fields and have complementary relationship with conventional technologies for technology progress of CoPS. It also implies that latecomers need to pursue integrated learning that includes emerging technologies as well as conventional technologies rather than independent learning related to emerging technologies for successful catch-up of CoPS. Our findings provide an important initial theoretical ground for investigating the emerging technologies and their characteristics in CoPS as well as recognizing knowledge management strategy for successful catch-up of latecomers. Our findings also contribute to the policy development of the CoPS from the perspective of innovation strategy and knowledge management.

• Journal of Radiation Protection and Research
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• 제20권1호
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• pp.53-64
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• 1995

월성 원자력발전소 2,3,4 호기의 보조건물 주요 지역에서 냉각재 다량상h7사고 (large LOCA) 후의 방사선장을 평가하였다. 핵분열 생성물의 총량은 ORIGEN2 코드를 사용하여 계산하였고 선원항은 2중고장 시나리오, 즉 LOCA 사고후 비상노심냉각 (ECC) 계통의 고장이 결부된 사고시의 방사능 방출에 근거하였다. 원자로건물, 보조건물 및 ECC 계통의 구조모형을 QAD-CG 모델에 포함하여 계산하였다. 사고시점부터 90일 경과시까지 시간대 별로 선량율과 누적선량을 계산하였다. 결과적으로, 연속출입이 요구되는 중요지역에서의 방사선장은 충분히 낮은 것으로 평가되었다. 그러나, 일부구역에서는 제한적인 출입을 허용할 정도로 상대적으로 높은 방사선장을 나타내었다.

• Korean Chemical Engineering Research
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• 제51권3호
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• pp.376-381
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• 2013

원유에 함유된 물질 중 분자량이 큰 파라핀계 왁스성분의 침전 거동을 연구하였다. 용해되어 녹아있는 왁스성분은 주위 온도가 낮아지면 침전을 시작한다. 침전이 시작되는 온도를 왁스침전온도라 하며, 왁스침전온도에 대해서는 다양한 측정 방법들이 연구되어 왔다. 이에 반하여, 온도하강에 따른 왁스 침전량, 즉 온도에 따른 정량화 시도는 상대적으로 많지 않다. 본 연구는 FTIR을 활용하여 온도에 따른 침전된 왁스의 정량화를 시도하였다. 기존에 제안된 방법이 FTIR의 한 밴드영역인 735~715 $cm^{-1}$에서 시도되었던 것과 비교하여, 본 연구에서는 두 밴드영역인 1,402~1,324 $cm^{-1}$와 735~715 $cm^{-1}$을 활용하였다. 이 방법을 이용하여 정량화를 시도하였을 때, 온도에 따른 부피변화가 있을 경우나 시료에 물이 함유된 경우와 같이 기존 방법에서는 측정이 불가능한 경우에도 안정적인 결과를 얻을 수 있었다.

• 한국산학기술학회논문지
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• 제20권6호
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• pp.306-313
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• 2019

전 세계적으로 자동차 산업에 있어서 현재 배기가스로 인한 대기오염과 화석연료의 에너지자원 고갈의 문제로 인해 배기가스 발생이 전혀 없고 다양한 방법으로 에너지원을 만들 수 있는 전기자동차의 전동 구동부 시스템에 대한 연구가 활발히 진행되고 있다. 이러한 전기 자동차는 차량의 중량에 따라 모터의 용량 및 사양이 달라지는데 그 중 상용전기자동차에 사용하는 고용량의 전기모터는 크기가 크고 중량이 무거워서 제한된 배터리의 용량을 빨리 소비하여 주행거리를 단축시킨다. 이러한 모터의 출력은 일반적으로 고속회전하기 때문에 자동차에 필요한 초기가속능력이 부족하다. 따라서 본 연구에서는 모터의 출력을 변속기를 통하여 감속시켜 차량의 초기가속능력을 높이고 모터의 크기와 중량을 상대적으로 줄였다. 그리고 각각의 분리된 구조를 이루고 있는 구동모터와 변속기를 일체화하여 입 출력을 위한 커넥터의 간소화를 이루고 냉각시스템의 용량도 축소하여 차량을 설계하고 제작하거나 기존차량을 구조변경을 하는데 효과적인 기술을 제시하였다. 또한 모터와 변속기를 일체화하기 위한 스플라인의 설계 및 해석을 통하여 적합성을 증명하였다.

• 한국건축친환경설비학회 논문집
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• 제12권6호
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• pp.669-679
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• 2018

Energy consumption savings in buildings should be reviewed in diverse areas such as air conditioning system and lighting responsible for cooling and heating, and energy management systems such as BAS (Building Automation System) and BEMS (Building Energy Management System) are introduced to improve energy consumption efficiency and to promote economic control of related facilities by integrated management of energy generated and consumption in buildings. The measured building of this study uses regenerative geothermal system. Measured values of heat pump and system COP were 4.7 and 4.2 respectively, and they were found to be higher 11.9% and 23.5% than rated values. As a result of analyzing the air conditioning and lighting energy from the first floor to the fourth floor performing the air conditioning, the second and third floors, which have a high frequency of use, are compared with the first and fourth floors 50% higher energy consumption ratio. On the other hand, the general heat storage system uses the nighttime power of the previous day to store heat and use it the next day. The total number of days of abnormal operation during the summer season is 61 days. The electricity cost corresponding to the abnormal operation is 1,840,641 KRW, and the normal operation using the nighttime power is 1,363,561 KRW, which is difference of 477,080 KRW, 35% increase in cost. We will utilize it as the main data of BEMS through analysis of winter operation characteristics as well as summer operation characteristics.

• 한국기계가공학회지
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• 제20권7호
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• pp.33-40
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• 2021

Current industrial flow is directed toward reducing the usage of raw materials by reusing parts, which is referred to as a circular economy (CE). Repair is one of the most value-added approaches in CE, which can be efficiently accomplished via additive manufacturing. The repair technology of metallic parts via the directed energy deposition process, which includes the selective removal and redeposition of damaged regions of metallic parts. Residual stress characteristics depend on the shape of the part and the shape of the redeposition region. The objective of this study is to investigate the effects of the radius and corner position of the substrate on the residual stresses for repair by using finite element analysis (FEA). The residual stress distribution of the 45° angle groove at the edge of the circular shape models on the outer and inner radii was analytically investigated. The analysis was accomplished using SYSWELD software by applying a moving heat source with defined material properties and cooling conditions integrated into the FEA model. The results showed a similar pattern of concentrated stress distribution for all models except the 40-mm and 60-mm radii, for which the maximum stress locations were different. The maximum residual stresses are high but lower than the yield strength, suggesting the absence of cracks and fractures due to residual stresses.

• 생물환경조절학회지
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• 제30권4호
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• pp.429-440
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• 2021

본 연구는 고온기 원예작물의 안정 생산을 위해 대형 단동하우스 '사계절하우스'를 파프리카 재배에 활용 시 시설 내부 기상환경 및 파프리카 품종별 생육, 수량, 품질 등을 분석하고 근권냉방 효과 등을 구명하여 파프리카 재배환경 조건을 최적화 하기 위한 기초자료로 사용하고자 수행하였다. 정식 후부터 재배 종료 시점(2020년 5-11월)까지 시설내 평균 적산광량은 12.7MJ·m^-2d^-1로, 온실외부의 평균 광량인 14.1MJ·m^-2d^-1의 90% 수준으로 나타났다. 일 년중 가장 기온이 높은 7-8월의 온실내 24시간 평균온도는 외기보다 3.04℃ 낮았고, 장마가 끝난 8월 12일 이후에는 평균 4.07℃ 낮게 나타났다. 시설 내 포그 냉방 가동(6월 13일) 이전 일평균 상대습도는 최저 40%(주간 20%) 수준까지 떨어져 작물재배에 적합하지 않은 상태였으나 포그를 가동한 이후 주간 상대습도는 70-85% 수준으로 증가된 것으로 나타났다. 평균 수분부족분(humidity deficit)은 포그 공급전에는 최고 12.7g/m³ 까지 상승하여 매우 건조한 조건이었으나, 포그 공급 후 고온기(7-8월)에 평균 3.7g/m³으로 감소하였고, 저온기(10-11월)로 갈수록 다시 증가되는 경향이었다. 주간 잔존 CO₂ 농도는 전체 재배기간동안 평균 707ppm으로 나타났다. '20년 7월 27일부터 11월 23일까지 수확한 파프리카의 품종별 상품수량(kg/10a)은 주황색 품종 'DSP-7054'과 황색 품종 'Allrounder'이 각각 14,255kg/10a와 14,161kg/10a로 다른 품종에 비해 높았고, 다음으로 주황색 'K-Gloria orange', 황색 'Volante', 적색 'Nagano' 품종 순으로 나타났다. 사계절하우스에서 고온기(8월)에 생산된 대과종 파프리카의 품종별 과실품질 특성을 조사한 결과, 과고, 과폭, 과실당도, 과육두께에서 품종 간 유의성이 인정되었다. 당도는 주황색 품종인 'DSP-7054'와 'Naarangi'에서 높게 나타났고, 과육두께는 황색과 주황색 품종인 'K-Gloria orange'와 'Allrounder'에서 높게 나타났다. 근권 냉방처리 기간 동안 배지내 일평균 온도는 20.7℃로 나타났고, 근권 난방처리 기간 동안 배지내 일평균 온도는 23.4℃로 나타났다. 근권부 냉난방 처리를 통해 상품수량은 무처리구에 비해 비해 'Nagano' 16.5%, 'Allrounder' 1.3%, 'Naarangi' 20.2%, 및 'Raon red' 17.3% 증가하였고, 품종 전체로는 16.1% 증가하였다. 근권 냉난방처리에 의해 과실의 경도는 4개 품종 평균 5.7% 증가하였으나 다른 품질 지표에서는 유의성있는 차이가 나타나지 않았다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.131.1-131.1
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• 2010

This study was conducted for engineering optimization for the gasification process which is the key factor for success of Taean IGCC gasification plant which has been driven forward under the government support in order to expand to supply new and renewable energy and diminish the burden of the responsibility for the reduction of the green house gas emission. The gasification process consists of coal milling and drying, pressurization and feeding, gasification, quenching and HP syngas cooling, slag removal system, dry flyash removal system, wet scrubbing system, and primary water treatment system. The configuration optimization is essential for the high efficiency and the cost saving. For this purpose, it was designed to have syngas cooler to recover the sensible heat as much as possible from the hot syngas produced from the gasifier which is the dry-feeding and entrained bed slagging type and also applied with the oxygen combustion and the first stage cylindrical upward gas flow. The pressure condition inside of the gasifier is around 40~45Mpg and the temperature condition is up to $1500{\sim}1700^{\circ}C$. It was designed for about 70% out of fly ash to be drained out throughout the quenching water in the bottom part of the gasifier as a type of molten slag flowing down on the membrane wall and finally become a byproduct over the slag removal system. The flyash removal system to capture solid particulates is applied with HPHT ceramic candle filter to stand up against the high pressure and temperature. When it comes to the residual tiny particles after the flyash removal system, wet scurbbing system is applied to finally clean up the solids. The washed-up syngas through the wet scrubber will keep around $130{\sim}135^{\circ}C$, 40~42Mpg and 250 ppmv of hydrochloric acid(HCl) and hydrofluoric acid(HF) at maximum and it is turned over to the gas treatment system for removing toxic gases out of the syngas to comply with the conditions requested from the gas turbine. The result of this study will be utilized to the detailed engineering, procurement and manufacturing of equipments, and construction for the Taean IGCC plant and furthermore it is the baseline technology applicable for the poly-generation such as coal gasification(SNG) and liquefaction(CTL) to reinforce national energy security and create new business models.