• 대한기계학회논문집B
• /
• 제33권6호
• /
• pp.418-426
• /
• 2009

The effect of an inertia moment of a pump flywheel on the thermal-hydraulic behaviors of the KALIMER-600(Korea Advanced LIquid MEtal Reactor) reactor pool during an early-phase of a loss of normal heat sink accident was investigated. The thermal-hydraulic analyses for a steady and a transient state were made by using the COMMIX-1AR/P code. In the present analysis a quarter of the reactor geometry was modeled in a cylindrical coordinate system, which includes a quarter of a reactor core and a UIS, a half of a DHX and a pump and a full IHX. In order to evaluate the effects of an inertia moment of the pump flywheel, a coastdown flow whose flow halving time amounts to 3.69 seconds was supplied to a natural circulation flow in the reactor vessel. Thermal-hydraulic behaviors in the reactor vessel were compared to those without the flywheel equipment. The numerical results showed a good agreement with the design values in a steady state. It was found that the inertia moment contributes to an increase in the circulation flow rate during the first 40 seconds, however to a decrease of it there after. It was also found that the flow stagnant region induced by a core exit overcooling decelerated the flow rate. The appearance of the first-peak temperature was delayed by the flow coastdown during the initial stages after a reactor trip.

• 방사성폐기물학회지
• /
• 제12권3호
• /
• pp.179-189
• /
• 2014

파이로 공정은 사용후핵연료 관리 이슈 해결과 유용자원 재활용 제고의 목적으로 개발되고 있다. 파이로 공정 중 전해환원 공정은 LiCl을 전해질로 사용하여 산화물을 금속으로 전환시키는 공정으로 금속 전환체에 잔류염이 포함되므로 후속 공정이 요구된다. 진공 증류 공정은 다양한 용융염계에서 적용되어 왔으며 금속 전환체에서도 활용될 수 있다. 전해환원 금속 전환체 잔류염은 LiCl과 알카리 및 알카리토 금속 염화물을 포함한다. 본 연구에서는 이들 염화물들의 증기압을 추산하여 진공 증류 공정에서 잔류 액체의 조성변화를 계산하였다. 증류된 기체가 일정하게 제거되는 조건에서 물질수지와 기-액 평형식을 결합한 모델을 개발하였으며 증기압을 이용하여 무차원 시간에 대한 액체 조성 변화를 계산하였다. 공정 조건 변화 모사를 위해 온도와 용융염 조성을 변화시켜 거동을 비교하였다. 잔류염의 증류는 주성분인 LiCl에 의해 지배되었으며 LiCl 보다 증기압이 높은 CsCl은 쉽게 제거될 것이 예상되었다. 증기압이 유사한 RbCl은 LiCl과 일정한 조성이 유지되었다. 반면 증기압이 낮은 $SrCl_2$와 $BaCl_2$는 시간에 따라 농축되며 초기 조성이 높은 경우 증류 과정에서 석출될 가능성이 있는 것으로 예상되었다.

• 분석과학
• /
• 제5권4호
• /
• pp.389-399
• /
• 1992

역상 액체 크로마토그래피에 의하여 $Pd(IEAA-NR)_2$ (R=H, $CH_3$, $C_2H_5$, $n-C_3H_7$, $C_6H_5-CH_2$, $n-C_4H_9$) 킬레이트의 용리 거동을 Micropak MCH-5 분리관을 사용하여 연구하고, 아울러 동시 분리분석에 미치는 흐름속도, 이동상의 세기, 분리관의 온도 등 여러 가지 인자들의 영향을 조사 검토하였다. 용리액으로 methanol/water의 이성분 용매를 사용하였으며, 모든 금속 킬레이트의 용매 세기 인자는 $0{\leq}log\;k^{\prime}{\leq}1$의 범위임을 확인하였고, 각 금속 킬레이트의 log k'과 이성분용매 중의 물의 부피분율을 도시한 결과 직선 관계가 성립하였다. 또한 뱃치법으로 측정한 분포비 ($D_c$)값과 k'값을 도시하여 본 결과 직선관계가 성립됨으로써 금속 킬레이트의 용리 메카니즘이 주로 소용매성 효과, 즉 소수성효과에 기인함을 확인하였다. 또한 금속 킬레이트의 머무름에 미치는 용량 인자와 온도와의 관계를 알아본 결과 좋은 직선성을 나타내고 있으며, 직선의 기울기로부터 엔탈피 (${\Delta}H$)와 엔트로피 (${\Delta}S$)를 구하고, 엔탈피와 용량 인자와의 관계로부터 금속 킬레이트의 머무름이 반드시 엔탈피와 관련되어 있다고 할 수 없으며 구조적 성질과도 관계가 있는 것으로 여겨진다.

• KEPCO Journal on Electric Power and Energy
• /
• 제2권3호
• /
• pp.447-452
• /
• 2016

It is imperative to develop an effective pathway to depolymerize lignin into liquid fuel that can be used as a bioheavy oil. Lignin can be converted into liquid products either by a solvent-free thermal cracking in the absence air, or thermo-chemical degradation in the presence of suitable solvents and chemicals. Here we show that the solvent-assisted liquefaction has produced promising results in the presence of metal-based catalysts. The supercritical ethanol is an efficient liquefaction solvent, which not only provides better solubility to lignin, but also scavenges the intermediate species. The concentrated sulfuric acid hydrolysis lignin (CSAHL) was completely liquefied in the presence of solid catalysts (Ni, Pd and Ru) with no char formation. The effective deoxy-liquefaction nature associated with scEtOH with aid hydrodeoxygenation catalysts, resulted in significant reduction in oxygen-to-carbon (O/C) molar ratio up to 61%. The decrease in oxygen content and increase in carbon and hydrogen contents increased the calorific value bio-oil, with higher heating value (HHV) of $34.6MJ{\cdot}Kg^{-1}$. The overall process is energetically efficient with 129.8% energy recovery (ER) and 70.8% energy efficiency (EE). The GC-TOF/MS analysis of bio-oil shows that the bio-oil mainly consists of monomeric species such as phenols, esters, furans, alcohols, and traces of aliphatic hydrocarbons. The bio-oil produced has better flow properties, low molecular weight, and high aromaticity.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
• /
• pp.545-550
• /
• 2002

In order to ensure the signal could be transported cocrrectly, the microwave devices made of Aluminmn alloys must be assembled and brazed flaw-freely. In this paper, a new approach of using contact reactive brazing (CRB) process to realize the compact brazing of Aluminum alloys was put forward. The reason for this is that CRB, which realizes bonding depending on the liquid alloy produced by metallurgy reaction between the materials to be joined, overcomes the limitation of traditional brazing that the macroscopically disorganized filling flow of liquid filler metal would result in defects in brazed seam. Joint ofLF21 (AA3003) with the compactness of over 95% was brazed by the method of CRB using Si powder as an interlayer. At last, the influence of the physical parameter related to the Si powder interlayer on the compactness of the joints was investigated in detail.

• 소성∙가공
• /
• 제8권3호
• /
• pp.301-301
• /
• 1999

Austenitic stainless steels such as AISI 316L have been used in equipment in which fluid flows at high speeds which can induce cavitation erosion on metallic surfaces due to the collapse of cavities, where the collapse is caused by the sudden change of local pressure within the liquid. Usually AISI 316L is susceptible to cavitation erosion. This research focuses on developing a better material to replace the AISI 316L used in equipment with high speed fluid flow, such as impellers. The effects of Rare Earth Metal (REM) additions on the cavitation erosion-corrosion resistance of duplex stainless steels were studied using metallographic examination, the potentiodynamic anodic polarization test, the tensile test, the X-ray diffraction test and the ultrasonic cavitation erosion test. The experimental alloys were found to have superior mechanical properties due to interstitial solid solution strengthening, by adding high nitrogen (0,4%), as well as by the refinement of phases and grains induced by fine REM oxides and oxy-sulfides. Corrosion resistance decreases in a gentle gradient as the REM content increases. However, REM containing alloys show superior corrosion resistance compared with that of other commercial alloys (SAF 2507, AISI 316L). Owing to their excellent mechanical properties and corrosion resistance, the alloys containing REM have high cavitation erosion-corrosion resistance.

• Bulletin of the Korean Chemical Society
• /
• 제24권10호
• /
• pp.1433-1436
• /
• 2003

A new method for the simultaneous determination of heavy metal ions in cigarette material by microwave digestion and reversed-phase high-performance liquid chromatography (RP-HPLC) has been developed. The cigarette material was digested by microwave digestion. Lead, cadmium, mercury, nickel and tin ions in the digested samples were pre-column derivatized with tetra-(2-chlorophenyl)-porphyrin ($T_2$-CPP) to form color chelates, which were then enriched by solid phase extraction with a $C_{18}$ cartridge. The chelates were separated on a Waters Xterra$^{TM}RP_{18}$ column by gradient elution with methanol (containing 0.05 mol/L pyrrolidine-aceticacid buffer salt, pH = 10.0) and acetone (containin0.05 mol/L pyrrolidine-acetic acid buffer salt, pH = 10.0)as mobile phase at a flow rate of 0.5mL/min and analyzed with a photodiode array detector from 350-600 nm. The detection limits of lead, cadmium, mercury, nickel and tin were 4,3,3,8 and 5 ng/L, respectively, in the original samples. This method was afforded good results.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2005년도 춘계학술대회 논문집
• /
• pp.174-179
• /
• 2005

In the super slow speed die casting process, the casting defects due to melt flow should be controlled in order to obtain sound casting products. The casting defects that are caused by molten metal were cold shut formation, entrapment of air, gas, and inclusion. But the control of casting defects has been based on the experience of the foundry engineers. The calculation of simulation can produce very useful and important results. The calculation data of die casting process condition from the computer simulation by the Z-CAST is made to insure that the liquid metal is injected at the right velocity range and that the filling time is small enough to prevent premature solidification. The parameters of runner shape that affected on the optimized conditions that was calculated with simple equation were investigated. These die casting process control techniques of automobile valve body mid-plate have achieved good agreement with the experimental data of tensile strength, hardness test, and material structure photographies satisfactory results.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회B
• /
• pp.3175-3180
• /
• 2008

A metal-fueled pool-type liquid metal fast reactor (LMFR) provides large margins to sodium boiling and fuel damage under accident conditions. The favorable passive safety results are obtained by both a reactivity feedback mechanism in the core and a passive decay heat removal system. Among the various reactivity feedbacks, the ones by a thermal expansion of a radial dimension of the core and by the control rod drivelines are strongly dependent on the flow conditions in the core and the hot pool, respectively. The effects of multidimensional thermal hydraulic characteristics on these reactivity feedbacks are investigated by the system-wide safety analysis code SSC-K with advanced thermal hydraulics models. Particularly a detailed three dimensional thermal hydraulics reactor core model is integrated into SSC-K for use in a whole system analysis of the passive safety aspects of LMR designs. The model provides fuel and cladding temperatures for every fuel pin in a reactor and coolant temperatures for every coolant sub-channel in the reactor.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2005년도 추계 학술대회논문집
• /
• pp.105-110
• /
• 2005

Evaluation of elliptic blending turbulence model (EBM) together with the two-layer model, shear stress transport (SST) model and elliptic relaxation model (V2-F) is performed for a better prediction of thermal stratification in an upper plenum of a liquid metal reactor by applying them to the experiment conducted at JNC. The algebraic flux model is used for treating the turbulent heat flux. There exist much differences between turbulence models in predicting the temporal variation of temperature. The V2-F model and the EBM better predict the steep gradient of temperature at the interface of thermal stratification, and the V2-F model and EBM predict properly the oscillation of temperature. The two-layer model and SST model fail to predict the temporal oscillation of temperature.