• Nuclear Engineering and Technology
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• 제47권5호
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• pp.534-545
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• 2015

In the very high temperature reactor (VHTR), which is a next generation nuclear reactor system, ceramics are used as a fuel coating material and graphite is used as a core structural material. Even if a depressurization accident occurs and the reactor power goes up instantly, the temperature of the core will change only slowly. This is because the thermal capacity of the core is so high. Therefore, the VHTR system can passively remove the decay heat of the core by natural convection and radiation from the surface of the reactor pressure vessel. The objectives of this study are to investigate the heat transfer characteristics of natural convection of a one-side heated vertical channel with inserted porous materials of high porosity and also to develop the passive cooling system for the VHTR. An experiment was carried out using a one-side heated vertical rectangular channel. To obtain the heat transfer and fluid flow characteristics of the vertical channel with inserted porous material, we have also carried out a numerical analysis using a commercial Computational Fluid Dynamics (CFD) code. This paper describes the thermal performances of the one-side heated vertical rectangular channel with an inserted copper wire of high porosity.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1604-1615
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• 2023

In an open-pool type research reactor with a downward forced flow in the core, pipes can be under sub-atmospheric pressure because of the large pressure drop at the reactor core in the atmospheric pool. Sub-atmospheric pressure can result in air inflow into the pipe from the pressure difference between the atmosphere and the inside of the pipe, which in a postulated pipe break scenario can lead to the breakdown of the cooling pump. In this study, a plant-scale experiment was conducted to study air inflow in large piping systems by considering the actual operational conditions of an advanced research reactor. The air inflow rate was measured, and the entrained air was visualized to investigate the behavior of air inflow and flow regime depending on the pipe break size. In addition, the developed drift-flux model for a large vertical pipe with a diameter of 600 mm was compared with other correlations. The flow regime transition in a large vertical pipe under downward flow was also studied using the newly developed drift-flux model. Consequently, the characteristics of two-phase flow in a large vertical pipe were found to differ from those in small vertical pipes where liquid recirculation was not dominant.

• 자원환경지질
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• 제53권6호
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• pp.695-701
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• 2020

본 연구는 중성의 pH 조건에서 Fe, Mn, As이 포함된 복합오염수를 배출하는 광산배수의 수질특성을 모니터링하였다. 침출수를 처리하기 위해 모래와 석회석으로 이루어진 수직흐름반응조(VFR, Vertical Flow Reactor)와 제강슬래그와 석회석을 적용한 반응조(ZMR)로 구성된 현장파일럿 장치를 설치하여 약 6개월간 운영하였다. 광산배수 내 존재하는 Fe, Mn, As에 대한 현장파일럿 장치의 처리효율을 평가하였다. 중성의 알칼리 수질특성을 가진 D광산 침출수에 VFR와 ZMR 공정을 적용한 결과, pH와 알칼리도가 효과적으로 상승하여 Fe과 As가 99%이상 제거되었으며 Mn은 98%이상 제거하여 복합오염물질 처리가 가능함을 확인하였다. 본 연구결과를 통해 Fe, As, Mn이 포함된 소규모 광산배수에 자연정화기반의 공법이 적용가능함을 확인하였다.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.357-373
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• 2022

The high-temperature gas-cooled reactor pebble-bed module project is the first commercial Generation-IV NPP(Nuclear Power Plant) in China. A new joint is used for the vertical support of RPV(Reactor Pressure Vessel). The steel corbel is integrally embedded into the reactor-cabin wall through eight asymmetrically arranged pre-stressed high-strength bolts, achieving the different path transmission of shear force and moment. The vertical monotonic loading test of two specimens is conducted. The results show that the failure mode of the joint is bolt fracture. There is no prominent yield stage in the whole loading process. The stress of bolts is linearly distributed along the height of corbel at initial loading. As the load increases, the height of neutral axis of bolts gradually decreases. The upper and lower edges of the wall opening contact the corbel plate to restrict the rotation of the corbel. During the loading, the pre-stress of some bolts decreases. The increase of the pre-stress strength ratio of bolts has no noticeable effect on the structure stiffness, but it reduces the ultimate bearing capacity of the joint. A simplified calculation model for the elastic stage of the joint is established, and the estimation results are in good agreement with the experimental results.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 추계학술발표회논문집(2)
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• pp.1021-1026
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• 1995

The seismic responses of a base isolated Pressurized Water Reactor (PWR) are investigated using a mathematical model which expresses the superstructure as lumped mass-spring model and the seismic isolator as an equivalent spring-damper. Time history analyses are performed for the 1940 E1 Centre earthquakes in both horizontal and vertical directions. In the analysis, structural damping of 5% is used for the superstructure. The isolator damping ratios of 12% for horizontal and 5% for vertical directions are used. The acceleration responses in base isolated PWR superstructure with high damping rubber bearings are much smaller than those in fixed base structure in horizontal direction. However, the vertical acceleration responses at the superstructure in the base isolation system are amplified to some extent. It is suggested that the vertical seismic responses at the superstructure should be reduced by introducing a soft vertical isolation device.

• 유기물자원화
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• 제15권4호
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• pp.115-124
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• 2007

다량의 유기성 폐기물을 신속히 처리하기 위한 대용량의 반응조 개발이 이루어짐에 따라 대형 반응조 내부에서 재료물질 자체의 물리적 특성변화가 퇴비화에 미치는 영향을 파악하기 위한 연구가 시도되고 있다. 특히 좁은 공간에서 단위 면적당 처리량을 높일 수 있는 수직형 반응조에서는 재료가 갖는 자체적인 무게로 인한 침하 현상이 발생하여 퇴비화공정에 영향을 미치게 된다. 본 연구에서는 수직형 퇴비화 반응조 내에서의 수직 높이구간별로 재료물질의 온도, 수분함량, 용적밀도, 고형물함량, 침하거리 등의 물리적 성상 변화를 측정하여 수직형 반응조에서의 침하현상에 의한 효과를 파악하고자 하였다. 이를 위하여 수직형 퇴비화 반응조를 제작하여 계분과 톱밥을 혼합한 퇴비화 재료를 투입한 후 일정한 공기 유량을 주입하면서 퇴비화기간 동안의 반응조 높이별 물리적 성상 변화를 측정 하였다. 실험결과, 각 높이구간별로 최대온도 이후의 온도 재상승에 의한 변동폭은 교반횟수가 증가함에 따라 감소하고 있으며, 각 수직 높이 구간별로는 수직높이가 높아질수록 온도상승폭이 증가하고 있다. 수분함량 변화는 하층부에서의 증발수분이 상층구간으로 이동하게 됨으로써 반응조 높이가 높아질수록 수분함량이 높아지는 결과가 나타났다. 용적밀도는 수분함량 변화와 유사한 경향을 나타내었으며, 수분함량과 용적밀도와는 2차식($R^2=0.94$)의 관계를 보이고 있다. 각 높이구간에서의 고형물 함량은 수직높이가 높아질수록 감소하는 것으로 나타났다. 이와 같은 수직형 반응조에서의 높이구간별 물리적 성상변화는 퇴비화 재료물질의 침하현상에 기인한 것으로 나타났으며, 퇴비화 재료물질의 침하거리를 시간에 따른 1차식($R^2=0.91$)으로 나타내면 Ls(침하거리, cm)=$2.184{\times}T$(시간, day)와 같은 관계식을 얻을 수 있었다. 이러한 수직형 반응조내 재료물질의 침하현상은 자유공기공극(FAS)을 폐쇄시키고 공기투과성(air permeability)을 감소시켜 국부적으로 공기흐름을 저해하거나 혐기성 상태를 유발시키는 원인이 된다.

• 한국가시화정보학회지
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• 제16권1호
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• pp.37-41
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• 2018

The two-fluid model is widely used for practical applications involving multi-phase flows in chemical reactor, nuclear reactor, desalination systems, boilers, and internal combustion engine. There are several modeling terms in the two-fluid model, which must be determined properly. This study suggests the best models for turbulent vertical bubbly flow.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.561-568
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• 2001

For obtaining the time history nodal responses of reactor building, a lumped-mass beam model composed of two sticks for the reactor building and the reactor support structure is developed. The time history responses for the non-isolated and isolated reactor buildings are calculated under an artificial time history, generated using the seismic spectrum curve of US NRC RG1.60. The analysis results show that the horizontal accelerations of the isolated building are dramatically decreased to one-tenths of the non-isolated one, but the vertical responses are increased by about 40%.

• Nuclear Engineering and Technology
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• 제49권3호
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• pp.476-483
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• 2017

The decay heat that is produced by nuclear reactor spent fuel must be cooled in a spent fuel storage pool. A wickless heat pipe or a vertical two-phase closed thermosyphon (TPCT) is used to remove this decay heat. The objective of this research is to investigate the thermal performance of a prototype model for a large-scale vertical TPCT as a passive cooling system for a nuclear research reactor spent fuel storage pool. An experimental investigation and numerical simulation using RELAP5/MOD 3.2 were used to investigate the TPCT thermal performance. The effects of the initial pressure, filling ratio, and heat load were analyzed. Demineralized water was used as the TPCT working fluid. The cooled water was circulated in the water jacket as a cooling system. The experimental results show that the best thermal performance was obtained at a thermal resistance of $0.22^{\circ}C/W$, the lowest initial pressure, a filling ratio of 60%, and a high evaporator heat load. The simulation model that was experimentally validated showed a pattern and trend line similar to those of the experiment and can be used to predict the heat transfer phenomena of TPCT with varying inputs.

• 한국염색가공학회지
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• 제12권1호
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• pp.32-43
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• 2000

Batch culture system and continuous culture systems were used to investigate the removal of disperse dye using white rot fungi. White rot fungi used in the study were Coriolus hirsutus IFO 4917, Lenzites betulina IFO 6266, Coriolus versicolor IFO 30340 and Phanerochaete chrysosporium IFO 31249. The results of the batch culture experiment showed that white rot fungi used in this study had excellent dye removal abilities. Phnerochete chrysosporium IFO 31249 was especially effective on the removal of disperse dyes. And continuous treatment of disperse red 60 was studied under two type of reactor using Phanerochaete chrysosporium IFO 31249. The removal efficiency of disperse red 60 for immobilized Phanerochaete chrysosporium IFO 31249 in continuous reactor with vertical matrix was increased 1.3 fold in $1.4\;hr^{-1}$ dilution rate when compared with continuous reactor without vertical matrix.