• Nuclear Engineering and Technology
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• 제50권1호
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• pp.80-87
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• 2018

Consideration is given to the possibility to use changes in buoyancy as a negative reactivity feedback mechanism during temperature transients in heavy liquid metal fast reactors. It is shown that by the proper use of heavy pellets in the fuel elements, fuel rods could be endowed with a passive self-ejection mechanism and then with a negative feedback. A first estimate of the feasibility of the mechanism is calculated by using a simplified geometry and model. If in addition, a neutron poison pellet is introduced at the bottom of the fuel, then when the fuel element is displaced upward by buoyancy force, the reactivity will be reduced not only by disassembly of the core but also by introducing the neutron poison from the bottom. The use of induced buoyancy opens up the possibility of introducing greater amounts of actinides into the core, as well as providing a palliative solution to the problem of positive coolant temperature reactivity coefficients that could be featured by the heavy liquid metal fast reactors.

• 융복합기술연구소 논문집
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• 제3권2호
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• pp.1-6
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• 2013

The ionic liquids are known to potential alternative solvents capable of replacing the commercial solvents in various processes including those in nuclear fuel cycle. As to the material, a number of studies have already reviewed the interesting results and addressed the spectroscopic as well as electrochemical behaviors of metal elements included in spent nuclear fuels. It has found that the important properties of metal ions in TBP dissolved ILs have led the development of alternative technologies to traditional solvent extraction processes. On the other hand, the electrochemical deposition of metal ions in ILs have been investigated for the application of the solvents to aqueous as well as to non-aqueous processes. In this work, a review on the application of ILs in nuclear fuel cycle is briefly presented to understand the notable researches on ILs focusing on aqueous processes.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1993년도 봄 학술발표회논문집
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• pp.191-198
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• 1993

This paper presents the analysis briefs to evaluate the structural adequacy of the KMRR spent fuel storage racks which stack modules in three layers. The seismic analysis models are idealized to consider the overall dynamic motions such as rocking, sliding and liftoff in the event of an postulated earthquake. The displacement time histories of the floor obtained from the floor response spectra in three orthogonal directions are simultaneously applied to the nonlinear seismic model of the structure with gap and friction elements.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.90.1-90.1
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• 2010

The design and fabrication of a metallic bipolar plate-gasket assembly for polymer electrolyte fuel cells (PEMFCs) is defined. This bipolar plate-gasket assembly was prepared by inserting a previously prepared bipolar plate in the specially designed gasket mold. For this aim, a proprietary fluoro-silicone based rubber was injected directly into the bipolar plate borders. Gaskets obtained like this showed the chemically / physically stable and the good sealibilty in typically operating PEM fuel cell conditions. And also, this bipolar plate-gasket assembly shows lots of advantages with respect to traditional PEMFCs stack assembling systems: useful application to automative stacking due to easy handling, reduced fabrication time, possibility of quality control and failed elements substitution. This bipolar plate-gasket assembly was evaluated in the short fuel cell stack and met the leakage requirement for normal operation both in short-term and in long-term operation. Especially, it was confirmed that this gasket could be applied successfully even in the high pressure FEM fuel cell systems(over 2.0 bar in absolute pressure).

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.2847-2858
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• 2021

When a nuclear reactor with rectangular fuel assemblies runs for a long time, impurities and debris may be taken into coolant channels, which may cause flow blockage, and the blocked fuel assemblies might be destroyed. Therefore, the purpose of this study is to perform a thermal-hydraulic analysis of a rectangular fuel assembly by STAR-CCM+, under the condition of one subchannel with 80% blockage ratio. A rectangular fuel assembly of the International Atomic Energy Agency (IAEA) 10 MW material test reactor (MTR) is chosen. In view of the gasket material taken into the coolant channel is close to the single side of the coolant channel, in the flow blockage accident of the Oak Ridge Research Reactor (ORRR), a new blockage category called single side blockage is attempted. The blockage positions include inlet, middle and outlet, and the blockage is set as a cuboid. It is found by simulations that the blockage redistributes the mass flow rate, and large vortices appear locally. The peak temperature of the cladding is maximum, when the blockage is located at the single side of the coolant channel inlet, and no boiling occurs in all blockage cases. Moreover, as the height of the blockage increases, the damage caused by the blockage increases slightly.

• 방사성폐기물학회지
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• 제19권3호
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• pp.307-322
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• 2021

This study developed an analytical methodology for the mechanical integrity of spent nuclear fuel (SNF) cladding tubes under external pinch loads during transportation, with reference to the failure mode specified in the relevant guidelines. Special consideration was given to the degraded characteristics of SNF during dry storage, including oxide and hydride contents and orientations. The developed framework reflected a composite cladding model of elastic and plastic analysis approaches and correlation equations related to the mechanical parameters. The established models were employed for modeling the finite elements by coding their physical behaviors. A mechanical integrity evaluation of 14 × 14 PWR SNF was performed using this system. To ensure that the damage criteria met the applicable legal requirements, stress-strain analysis results were separated into elastic and plastic regions with the concept of strain energy, considering both normal and hypothetical accident conditions. Probabilistic procedures using Monte Carlo simulations and reliability evaluations were included. The evaluation results showed no probability of damage under the normal conditions, whereas there were small but considerably low probabilities under accident conditions. These results indicate that the proposed approach is a reliable predictor of SNF mechanical integrity.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.846-854
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• 2024

FEMAXI-ATF is being developed for fuel performance modeling of SiC cladded UO2 fuel with focuses on modeling pellet-cladding mechanical interactions (PCMI). The code considers probability distributions of mechanical strengths of monolithic SiC (mSiC) and SiC fiber reinforced SiC matrix composite (SiC/SiC), while it models pseudo-ductility of SiC/SiC and propagation of cladding failures across the wall thickness direction in deterministic manner without explicitly modeling cracks based on finite element method in one-dimensional geometry. Some hypothetical BWR power ramp conditions were used to test sensitivities of different model parameters on the analyzed PCMI behavior. The results showed that propagation of the cladding failure could be modeled by appropriately reducing modulus of elasticities of the failed wall element, so that the mechanical load of the failed element could be re-distributed to other intact elements. The probability threshold for determination of the wall element failure did not have large influence on the predicted power at failure when the threshold was varied between 25 % and 75 %. The current study is still limited with respect to mechanistic modeling of SiC failure as it only models the propagation of the cladding wall element failure across the homogeneous continuum wall without considering generations and propagations of cracks.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1826-1834
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• 2011

The traffic realizes that people come and go. The mobility is on the basis of location and time. The physical means for the traffic is composed of roads, vehicles and fuel. The current traffic services place emphasis on the physical elements. In the near future, with the current elements, the railroad service is considerably improved of through intangible factors including the customized customer services that the mobile-social network service is newly applied. The intangible things are connected to the increase of the time value for customers.

• 전력전자학회논문지
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• 제15권2호
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• pp.134-141
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• 2010

소형 PEM (Proton Exchange Membrane) 연료전지 시스템은 가습이 필요치 않아 상용화의 가능성이 크지만 그 제어 방법은 뚜렷하게 정립되어 있지 않다. 따라서 본 논문에서는 소형 PEM 연료전지 시스템의 제어를 위해 이중 루프 구조의 제어방식을 정립하고 DSP (Digital Signal Processor)를 이용하여 구현한다. 일반적으로 연료전지 시스템에서 제어의 핵심 요소는 크게 공기와 수소의 공급, 스택 내부의 수분 관리, 스택의 온도 관리로 나뉜다. 별도의 가습이 없이 공랭식으로 구동되는 소형 PEM 연료전지 스택의 제어에 있어서 팬은 스택의 공기 공급과 열관리 및 수분관리를 위한 핵심적인 역할을 하며, 퍼지밸브는 스택 내부의 잉여수분을 배출한다. 제안된 방식은 이중 제어루프를 이용한 팬의 제어를 통해 팬의 과도응답을 빠르게 하여 공기의 공급 속도를 개선시키며, 연료전지 스택의 전압변화를 피드백 하여 보상해줌으로써 연료전지가 부하변동에 대해 신속한 응답 특성을 갖도록 하였다. 제안된 방법의 유용함은 60W급 소형 PEM 연료전지 시스템의 실험과 이를 이용한 노트북 컴퓨터의 구동을 통해 검증된다.

• 분석과학
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• 제15권1호
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• pp.1-6
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• 2002

사용후핵연료 침출액중 비방사능이 작은 핵종들의 정확한 분석을 위해서는 비방사능이 큰세슘을 제거하여야 한다. 이를 위하여 세슘만을 선택적으로 흡착한다고 알려진 ammonium molybdophosphate(AMP) 를 이용하여 사용후 핵연류 침출액의 구성원소들(Cs, U, Ce, La, Co, Sr)과 사용후핵연료와 접한 벤토나이트의 성분들(Ca, Na, K)에 대한 제거율을 검토하였다. 그 결과 0.1 M 질산매질에서 AMP로 90% 이상의 세슘이 제거되었고 대부분의 Ca, Na, Co, Sr은 용액중에 남아 있었다. 그러나 일부 세늄을 포함한 란탄족 3가 이온들은 세슘과 같이제거 되었다. 벤토나이트 성분중일부 칼륨도 AMP에 흡착하였으나 실제 시료와 같이 묽은 벤토나이트 용액에서의 칼륨은 AMP이 유효치환량에 큰 영향을 주지 않았다. 한편 사용후핵연료의 침출 기준원소인 스트론튬을 분리하기 위하여 8.0 M 질산매질의 용리할 경우 95% 이상의 스트론튬을 회수 할 수 있었다.