• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.41-49
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• 2003

Tube oscillation behaviour is experimentally investigated for the study on the fuel rod fretting that is caused by the flow-induced vibration in nuclear reactor. The experiment was conducted in all at room temperature. The specimen of tube assembly was supported by plate springs which simulated the spacer grids and fuel rods of a fuel assembly. To investigate the influence of contact condition between the grids and rods, normal load of 10 and 5 N, gaps of 0.1 and 0.3 mm were applied. The range of the oscillation at the center of the fuel rod specimen was varied as 0.2, 0.3 and 0.4 mm to simulate the fuel rod vibration due to flow. Displacements near the contact were measured with four displacement sensors during the tube oscillation. As results, the shape of oscillation (phase) varied depending on the contact condition. The oscillation displacement increased considerably from the contact to gap condition. The displacement increased further as the gap size increased. It is regarded that the spring shape influences the tube oscillation behaviour. Simple calculation showed that the slip displacement was very small. Therefore, cumulative damage concept is necessary for the fuel rod wear. The mechanism of plowing is thought required to explain the severe wear in the case of gap existence.

• 청정기술
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• 제13권4호
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• pp.293-299
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• 2007

막-전극 접합체(membrane electrode assembly, MEA)의 설계인자 즉, 구성요소들이 직접 메탄올 연료전지의 성능에 미치는 영향을 알아보았다. MEA에서의 촉매층과 고분자 분리막의 계면저항을 줄이기 위하여 직접 코팅법을 사용하여 제조한 MEA 구조와 조성의 최적화를 실시하였으며, 기체 확산층, 촉매량, 고분자 전해질 분리막의 두께가 직접메탄을 연료전지의 성능에 미치는 영향을 알아보고, 전기화학적 분석법을 사용하여 성능향상 요인을 분석하였다. 본 연구를 통해 직접코팅법으로 제조한 MEA의 구조와 조성에 따른 성능변화 특성을 파악할 수 있었으며, 연료극과 공기극에 총 $4\;m/cm^2$ (Pt 기준)의 촉매를 사용하였을 때, $80^{\circ}C$ 1기압의 운전 조건하에서는 최고성능 $147\;mW/cm^2$, $60^{\circ}C$, 1기압의 운전 조건하에서는 최고성능 $100\;mW/cm^2$을 확보하였다.

• 항공우주시스템공학회지
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• 제7권4호
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• pp.49-54
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• 2013

A turbopump for a 75 ton class liquid rocket engine was tested at full speed for 20 seconds using model fluid. Liquid nitrogen is used for the oxidizer pump, water for the fuel pump, and hot gas for the turbine. The non-cavitating head of pump from the turbopump assembly test showed a good agreement with that from the pump component test. The relative difference of turbine efficiency between the turbopump assembly test and the turbine component test was 0.3% only. Suction performance from the turbopump assembly test was higher than that of pump component test, which resulted from the thermodynamic effect of cavitation.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 Proceedings of The 6th korea-china joint workshop on nuclear waste management
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• pp.156-164
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• 2005

The challenges China is facing in energy security are briefly discussed. Then, the development of nuclear power in China in the first half of 21 st century is envisioned, and it is expected that Generation-3 PWR nuclear power plants (NPPs) would be the leading units of nuclear power in the coming $30\~40$ years. As part of the nuclear power program, the R&D work on nuclear fuel cycle is generally proposed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2396-2401
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• 2007

Freon CHF experiments are carried out to investigate the CHF enhancements by mixing vane shapes of spacer grids in nuclear fuel assembly. The experiments were performed for a wide range mass flux, 50$\sim}$3000 kg/$m^2s$. Three kinds of spacer grids in 5${\times}$5 rod bundles are tested: no mixing vane grids, hybrid mixing vane grids, and split mixing vane grids. The CHF performances are compared along with the data belong to the PWR operating conditions based on a water equivalence through a fluid-to-fluid modeling method. The average of the data in this range is 16.4% for 37 data of hybrid vane grid and 12.5% for 24 data of split vane. In the lower mass flux, however, the split vane grid shows slightly higher performance than the hybrid vane grid.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.482-487
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• 2001

A CFD study was conducted to evaluate the nuclear fuel assembly coolant mixing that is promoted by the flow-mixing vanes on the grid spacer. Four mixing vanes (split vane, swirl vane, twisted vane, hybrid vane) were chosen in this study. A single subchannel of one grid span is modeled using the flow symmetry. The three mixing vanes other than swirl vane generate a large crossflow between the subchannels and a skewed elliptic swirling flow in the subchannel near the grid spacer. The swirl vane induces a circular swirling flow in the subchannel and a negligible crossflow. The split vane and the twisted vane were predicted to result in relatively larger pressure drop across the grid spacer. Since the average turbulent kinetic energy in the subchannel rapidly decreases to a fully developed level downstream of the spacer, turbulent mixing caused by the mixing vanes appears to be not as effective as swirling flow mixing in the subchannel. In summary, the CFD analysis represented the overall characteristics of coolant mixing well in a nuclear fuel assembly with the flow mixing vanes on the grid spacer. The CFD study is therefore quite useful for the development of an advanced flow-mixing vane.

• 한국전산유체공학회지
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• 제9권2호
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• pp.11-17
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• 2004

CFD analysis was performed to figure out flow behavior in the inlet plenum of new research reactor where coolant is injected to the flow tubes with the fuel assembly. The computation results showed that large-scale vortices are generated in the inlet plenum by flow stream injected from inlet pipe. These vortices are divided into small vortices and reversed their revolution. They may lead to flow-induced vibration of fuel assembly, moreover, which has been regarded as a cause of fretting wear of fuel assembly. Also there is an another important thing that average velocity of each flow-tube is uneven showing difference in maximum 18%. So it has been suggested that perforated baffle will be installed to prevent the formation of vortex in the inlet plenum. Two perforated baffles, one is flow skirt and the other is muffler type flow straightener, were proposed and their effect was evaluated using commercial CFD code, Fluent. According to CFD analysis for two perforated baffles, it was confirmed that both of them can prevent or reduce vortex formation in the inlet plenum and make average velocity of each flow tube more even.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2454-2463
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• 2021

The objective of this research is to the use of americium (AmO₂) as a burnable absorber effectively instead of conventional gadolinium (Gd₂O₃) for VVER-1200 reactor by analyzing its impacts on reactivity, power peaking factor (PPF), safety factor, and quality of the spent fuel. The assembly is burned to 60 GWd/t by using SRAC-2006 code and JENDL-4.0 data library for finding the optimum amount and effective way of using AmO₂ as a burnable absorber. From these studies, it is found that AmO₂ can decrease the excess reactivity like Gd₂O₃ without changing the criticality life span and enrichment of ²³⁵U. A homogeneous mixture of the 0.20% AmO₂+ 4.95% enriched UO₂ fuel rod (model MF-4) decreases the PPF than the reference assembly. The use of AmO₂+UO₂ in the integral burnable absorber (IBA) rod or the outer layer could also decrease the PPF up to 10 GWd/t but increases rapidly after 30 GWd/t, which could be a safety threat. The fuel temperature coefficient and void coefficient of the model MF-4 are the same as the reference assembly. In addition, 22% of initially loaded Am are burning effectively and contributing to the power production.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.911-919
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• 2021

In this paper, the design stress intensity values for the plate-type fuel assembly for research reactor are presented. Through a tensile test, the material properties of the cladding (aluminum alloy 6061) and structural material (aluminum alloy 6061-T6), in this case the yield and ultimate tensile strengths, Young's modulus and the elongation, are measured with the temperatures. The empirical equations of the material properties with respect to the temperature are presented. The cladding undergoes several heat treatments and hardening processes during the fabrication process. Cladding strengths are reduced compared to those of the raw material during annealing. Up to a temperature of 150 ℃, the strengths of the cladding do not significantly decrease due to the dislocations generated from the cold work. However, over 150 ℃, the mechanical strengths begin to decrease, mainly due to recrystallization, dislocation recovery and precipitate growth. Taking into account the uncertainty of the 95% probability and 95% confidence level, the design stress intensities of the cladding and structural materials are established. The presented design stress intensity values become the basis of the stress design criteria for a safety analysis of plate-type fuels.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1526-1533
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• 2022

Small modular reactors have garnered considerable attention in the recent years. Plate fuel elements exhibit a good application prospect in small modular pressurized water reactors for marine applications. Further, improved economic benefits can be achieved by extending the core lifetime of small modular reactors. However, it is necessary to realize a large initial residual reactivity for achieving a relatively long burnup depth finally. Thus, the selection of a suitable burnable poison (BP) is a crucial factor that should be considered in the design of small modular reactors. In this study, some candidate BPs are selected to realize the effective control of reactivity. The results show that ²³¹Pa₂O₃, ²⁴⁰Pu₂O₃, ¹⁶⁷Er₂O₃, PACS-J, and PACS-L are ideal candidates of BP, and since the characteristics of BP can increase the final burnup depth of assembly, the economic benefits are gained. Additionally, an optimal combination scheme of BPs is established. Specifically, it is proved that through a reasonable combination of BPs, a low reactivity fluctuation during the lifetime can be achieved, leading to a large final burnup depth.