• Nuclear Engineering and Technology
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• 제56권3호
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• pp.785-792
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• 2024

This article provides an overview of the design methodology used to develop a conceptual set of reactivity control mechanism of a micro reactor based on the U-Battery. The U-Battery is based on remote deployment and therefore it is favourable to provide a long fuel lifecycle. This is achieved by implementing a high fissile loading content, which proves challenging when considering reactivity control methods. This article follows the design methodology used to overcome these issues, with an emphasis on a new concept of a moveable moderator which utilises the size of the U-Battery as a small reduction in moderation provides a significant reduction in reactivity. The latest work on this project sees the moveable moderator investigated during a depressurised loss of forced coolant accident, where a reduction of moderator volume increases the maximum fuel temperature experienced. The overall conclusion is that the maximum fuel temperature is not significantly increased (4 K) due to the central reflector region relatively lower volumetric heat capacity compared to that of whole core. However, a small temperature increase is observed immediately after the transient due to the central reflector removal because it reaches energy equilibrium with the fuel region faster.

• Environmental Engineering Research
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• 제18권2호
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• pp.103-108
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• 2013

Vietnam is a developing country with the rate around 5%-6% per year, especially in urban areas. Rapidly developed urban areas lead to stress for infrastructure and the water supply is also stressed. In Hanoi city, total water capacity from the manufactories is around one million cubic meters per day and almost the entire main water source is groundwater but it is not enough to supply all of Hanoi's people, especially in the summer. A demo project is implemented in Hanoi University of Civil Engineering (HUCE) to produce drinking water by using the rainwater and membrane system and supply for people. In this project, rainwater is collected on the rooftop of the lecture building with an area of around $500m^2$ and $100m^3$ volumetric rainwater tanks. Afterwards, the rainwater is treated by the micro-membrane system and supplied to the tap water. Total cost for construction, technology and operation in the first year is around USD 48,558. In the long-term (15 yr) if HUCE invests in the same system, with $20m^3$ volumetric storage tank, it can provide drinking water for 500 staffs in every year. The cost of investment and operation for this system is lower than 30% compared to buying bottled water with the price USD 1.8/bottle. The drinking water parameters after treatment are pH, 7.3-7.75; turbidity, 0.6-0.8 NUT; total dissolved solids, 60-89 mg/L; coliform, 0; heavy metal similar with water quality in the bottle water in Vietnam.

• 환경위생공학
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• 제12권3호
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• pp.9-17
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• 1997

This research aims to remove nitrogen in the piggery wastewater by combined process with upflow anaerobic sludge blanket (UASB) and biofilm process. For the effective denitrification. anaerobic and anoxic reactors were connected to a reactor. The effluent of aerobix reactor was recycled equally with influent in the upper filter of anaerobic reactor for denitrification and outlet of UBF reactor was connected to the settling tank with $1.5{\;}{\ell}$ capacity and the settling sludge was repeatedly recycled to UASB zone. The organic loading rate of total reactor was operated from 0.4 to $3.1kgCOD/m^{3}/d$ and it was observed that the removal rate of TCOD was 80 to 95 percentage. Ammonia nitrogen was removed over 90 percentage in the less volumetric loading rate than $0.1{\;}kgN/m^{3}/d$. But because of non-limitation of organic materials, it was reduced to 70 percentage in the more volumetric loading rate than $0.6{\;}kgN/m^{3}/d$. But denitrification rate was observed 100 percentage in the all of loading rate. This is caused by the maintenance of optimum temperature, sufficient carbon source, and competition of electron acceptors. The results of COD mass balance at the $1.21{\;}kgCOD/m^{3}/d$ was observed with the 71.7% percentage of influent COD. It was revealed that the most part of organic materials was removed in the aerobic and the anaerobic reactor because 38.4 percentage was conversed into $CH_{4}$ gas and 11 percentage was removed in the aerobic reactor with cell synthesis and metabolism. Besides, 5.7% organics was used to denitrification reaction and 3.7% organics related to sulfate reduction.

• Radiation Oncology Journal
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• 제31권1호
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• pp.34-40
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• 2013

Purpose: To evaluate the predictive factors of radiation pneumonitis (RP) and associated changes in pulmonary function after definitive concurrent chemoradiotherapy (CCRT) in patients with non-small cell lung cancer (NSCLC). Materials and Methods: Medical records of 60 patients with NSCLC who received definitive CCRT were retrospectively reviewed. Dose volumetric (DV) parameters, clinical factors, and pulmonary function test (PFT) data were analyzed. RP was graded according to the CTCAE ver. 4.0. Percentage of lung volume that received a dose of threshold (Vdose) and mean lung dose (MLD) were analyzed for potential DV predictors. PFT changes were calculated as the difference between pre-RT and post-RT values at 3, 6, and 12 months after RT. Results: Twenty-two patients (37%) developed grade ${\geq}2$ RP. Among clinical factors, tumor location in lower lobe was associated with RP. Among the DV parameters, only MLD >15 Gy was associated with grade ${\geq}2$ RP. There were statistically significant decreases in PFT at all points compared with pre-RT values in grade ${\geq}2$ RP group. MLD was associated with forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) changes at 6 and 12 months. V10 was associated with FVC changes at 12 months. V20 and V30 were associated with FEV1 changes at 6 months and FVC changes at 12 months. Conclusion: After definitive CCRT in patients with NSCLC, MLD >15 Gy and lower lobe tumor location were predictors of grade ${\geq}2$ RP. Pulmonary functions were decreased after CCRT and the magnitude of changes was associated with DV parameters.

• Computers and Concrete
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• 제31권6호
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• pp.513-525
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• 2023

This research presents the experimental and theoretical evaluations on circular steel-fiber-reinforced-concrete (SFRC) columns reinforced by glass-fiber-reinforced-polymer (GFRP) rebar under the axial compressive loading. Test programs were designed to investigate and compare the effect of different parameters on the structural behavior of columns by performing tests. Theses variables included conventional concrete (CC), fiber concrete (FC), steel/GFRP longitudinal rebars, and transversal rebars configurations. A total of 16 specimens were constructed and categorized into four groups in terms of different rebar-concrete configurations, including GFRP-rebar-reinforced-CC columns (GRCC), GFRP-rebar-reinforced-FC columns (GRFC), steel-rebar-reinforced-CC columns (SRCC) and steel-rebar- reinforced-FC columns (SRFC). Experimental observations displayed that failure modes and cracking patterns of four groups of columns were similar, especially in pre-peak branches of load-deflection curves. Although the average ultimate axial load of columns with longitudinal GFRP rebars was obtained by 17.9% less than the average ultimate axial load of columns with longitudinal steel rebars, the average axial ductility index (DI) of them was gained by 10.2% higher than their counterpart columns. Adding steel fibers (SFs) into concrete led to the increases of 7.7% and 6.7% of the axial peak load and the DI of columns than their counterpart columns with CC. The volumetric ratio had greater efficiency on peak loads and DIs of columns than the type of transversal reinforcement. A simple analytical equation was proposed to predict the axial compressive capacity of columns by considering the axial involvement of longitudinal GFRP rebars, volumetric ratio, and steel spiral/hoop rebar. There was a good correlation between test results and predictions of the proposed equation.

• Journal of Biosystems Engineering
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• 제13권3호
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• pp.44-51
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• 1988

The objective of this study is to develop a grain handling system for loading, unloading and transporting of rough rice stored at the in-bin drying and storage (IBDS) developed by the Korea Advanced Institute of Science and Technology(KAIST). A mechanized Fain handling system consisted of a portable auger and a gate was developed and tested. The test results can be summarized as the following: 1) The loading capacity of the handling system developed is $16.2m^3/h$ (8.3 ton/h) for the Indica type rice and $13.0m^3/h$(7.3 ton/h) for the Japonica type. It is greater than that of manual handling as much as 2.5 - 2.7 times. 2) The unloading capacity of the handling system developed is $16.0m^3/h$(8.2 ton/h) for the Indica type rice and $12.6m^3/h$(7.0 ton/h) for the Japonica type. It is greater than that of the manual as much as 4.7 - 5.5 times. 3) For 3-ton capacity of the storage, the loading and unloading can be performed for 20 and 30 minutes by one man operation of equipment. while 60 and 120 minute for the manual of 2 men, respectively. 4) The volumetric efficiency of the system developed is 0.42 - 0.54 and the power efficiency is 4.0 - 4.4. 5) The break-even quantity of the handling system developed is about 38.6 ton($68.7m^3$) of rough rice and the initial investment for the system would be returned within five years for the most owners of the KAIST IBDS system.

• 대한토목학회논문집
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• 제31권4A호
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• pp.331-340
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• 2011

콘크리트 공시체의 압축강도와 연성성능을 향상시키기 위하여 섬유-강판 복합플레이트 fiber-sheet and steel-plate composite plate(FSP))의 적용을 실험적으로 연구하였다. FSP 보강재료, 앵커볼트 설치방법, 콘크리트 압축강도 등이 고려된 FSP 보강 콘크리트 공시체의 압축실험을 실시하였다. FSP 보강 콘크리트 공시체의 압축실험결과, FSP는 콘크리트 공시체의 압축강도와 변형저항성능을 크게 향상시켰다. FSP 보강 콘크리트 공시체의 압축성능은 FSP 보강재 종류, 앵커볼트 사용방법, 콘크리트 압축강도에 영향을 받는 것으로 나타났다. 앵커볼트를 사용한 FSP 보강 콘크리트 공시체 실험에서 측정된 FSP의 파단변형률은 FRP 보강 콘크리트 압축부재 실험에서 측정된 FRP 파단변형률보다 크게 측정되었다. FSP 파단변형률의 크기는 FSP의 보강효과에 영향을 미친다. FSP 보강 콘크리트 공시체 압축실험에서 측정된 축방향변형률, 원주방향변형률, 체적 변형률에 의한 FSP 내부 콘크리트의 손상상태를 분석하여 FSP 보강효과를 평가하였다. 연구결과, FSP 보강공법은 콘크리트 압축부재의 보강방법으로 실용적 기법이라 판단된다.

• 한국지반공학회논문집
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• 제35권11호
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• pp.7-14
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• 2019

압축 벤토나이트는 고준위폐기물을 처분하기 위한 공학적방벽 시스템에서 중요한 구성요소 중 하나인 완충재의 후보물질로 가장 적합한 것으로 고려되고 있다. 완충재는 처분공 내 사용후핵연료가 담긴 처분용기와 근계 암반 사이에 채워지는 방벽재로서 지하수 유입으로부터 처분용기를 보호하고, 방사성 핵종 유출을 저지한다. 처분 초기에는 처분용기로부터 발생하는 고온의 열량으로 인해 완충재의 포화도는 감소하지만, 그 후 주변 암반으로부터 유입되는 지하수로 인해 완충재의 포화도는 증가한다. 이렇듯 완충재는 처분 운영 조건에 따라 불포화에서 포화 상태로 도달하게 되기에 완충재의 불포화-포화 거동 특성은 공학적방벽의 전체 안전성을 좌우할 수 있는 중요한 입력자료이다. 따라서 본 연구에서는 국내 압축 벤토나이트 완충재에 대한 수분보유특성을 규명하고자 하였다. 처분 초기 온도 증가에 따라 완충재의 포화도가 감소하는 상황을 고려하여 상온에서부터 125도까지 압축 벤토나이트의 온도 증가에 따른 체적 함수비와 수분흡입력을 측정하였다. 또한 이를 상온에서 동일한 함수비에서의 수분보유능과 비교하였으며 상온에서의 수분흡입력은 1~15% 정도 크게 측정되었다.

• 대한토목학회논문집
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• 제33권5호
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• pp.1765-1775
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• 2013

콘크리트 공시체의 압축강도와 연성성능을 향상시키기 위하여 FRP 와이어의 적용을 실험적으로 연구하였다. 와이어 보강겹수와 콘크리트 압축강도의 변화가 고려된 와이어 보강 공시체의 압축실험을 실시하였다. FRP 와이어 보강 공시체 압축실험에서 측정된 축방향변형률, 원주방향변형률, 체적변형률에 의한 와이어 내부 콘크리트의 손상상태를 분석하여 와이어 보강효과를 평가하였다. FRP 와이어 보강 공시체의 응력-변형률 선도는 두 개의 직선구간과 변환구간으로 구성된 것으로 측정되었으며, 균열이후구간에서 응력상승거동하였다. 와이어 보강 공시체의 균열강도와 최대강도는 와이어 보강겹수에 비례하여 증가하는 것으로 평가되었다. 와이어가 3겹 보강된 35 MPa 공시체의 최대강도는 무보강 공시체의 압축강도보다 286% 높게 측정되었다. FRP 와이어 보강 공시체의 내부 콘크리트 파괴형태는 i) 수직균열 또는 경사균열파괴; ii) 수평균열파괴로 구분되었다. 특히, 수평균열파괴는 와이어에 의한 구속약화로 인하여 갑자기 내부 콘크리트가 팽창하는 부분과 와이어가 아직 내부 콘크리트를 효과적으로 구속하는 부분의 전단효과로 발생하였으며, 수평균열은 공시체의 중앙부를 기준으로 여러 면으로 발생하였으며, 와이어에 의한 구속효과가 우수한 공시체에 발생하였다. FRP 와이어 보강 공시체 압축실험에서 와이어 최대파단변형률에 대한 인장파단변형률의 비가 55-90%로 측정되었으며, 평균 69.5%로 나타났다. 이는 일반 FRP 시트 보강 공시체 실험에서 측정된 시트 파단변형률보다 다소 높은 값으로 FRP 와이어 보강 공법의 우수성을 입증한다.

• 청정기술
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• 제29권3호
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• pp.217-226
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• 2023

본 연구에서는 grand canonical 몬테카를로 전산모사 방법을 이용하여 정사각형 배열을 가지는 단일벽나노튜브에서 나노튜브의 직경과 가장 가까운 튜브들 사이의 거리의 함수로써 수소의 흡착특성을 연구하였다. 그리고 동일한 직경과 간격을 가지는 삼각형 배열을 이용하여 기하학에 대한 영향도 연구하였다. 수소-탄소 그리고 수소-수소의 인력은 단거리 인력의 경우 Lennard-Jones 포텐셜을 사용하였고, 수소-수소의 경우는 정전기적 인력을 저온에서의 양자효과를 고려하기 위해 추가하였다. 194.5 K에서 큰 직경을 가지는 단일벽나노튜브의 경우 Type I과 넓은 간격을 가지는 나노튜브의 경우 흡착과 탈착과정에서 Type IV의 흡착 등온선이 관찰되었다. 200 bar에서 단일벽나노튜브의 중량 수소저장 능력은 미국 에너지부의 목표치에 도달하거나 초과하였다. 그러나 부피 수소저장 능력은 목표치의 약 70%에 해당하였다. 77 K에서는 단일층 형성과 이후 응축 단계가 따르는 두 단계의 흡착이 관찰되었다. 수소는 나노튜브의 내부 표면, 외부 표면, 관 내부의 공간 그리고 나노튜브 다발 사이의 틈새 채널의 순서로 흡착하였다. 1 bar 이하에서도 여러 가지 직경과 간격을 가지는 탄소나노튜브는 중량 그리고 부피 저장 능력이 모두 목표치를 초과하였다.