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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Nuclear Engineering and Technology
Journal Basic Information
Journal DOI :
Korean Nuclear Society
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Volume & Issues
Volume 44, Issue 8 - Dec 2012
Volume 44, Issue 7 - Oct 2012
Volume 44, Issue 6 - Aug 2012
Volume 44, Issue 5 - Jun 2012
Volume 44, Issue 4 - May 2012
Volume 44, Issue 3 - Apr 2012
Volume 44, Issue 2 - Mar 2012
Volume 44, Issue 1 - Feb 2012
Selecting the target year
NEW FRONTIERS IN THERMAL PLASMAS FROM SPACE TO NANOMATERIALS
Boulos, Maher I. ;
Nuclear Engineering and Technology, volume 44, issue 1, 2012, Pages 1~8
DOI : 10.5516/NET.77.2012.001
Thermal plasma technology has been at the center of major developments over the past century. It has found numerous applications ranging from aerospace materials testing to nanopowder synthesis and processing. In the present review highlights of principal breakthroughs in this field are presented with emphasis on an analysis of the basic phenomena involved, and the potential of the technology for industrial scale applications.
THERMAL PLASMA SYNTHESIS OF NANO-SIZED POWDERS
Seo, Jun-Ho ; Hong, Bong-Guen ;
Nuclear Engineering and Technology, volume 44, issue 1, 2012, Pages 9~20
DOI : 10.5516/NET.77.2012.002
A brief review on the thermal plasma synthesis of nano-sized powders is presented according to the application materials, such as, metals, ceramics, glasses, carbonaceous materials and other functional composites, such as, supported metal catalyst and core-shell structured nano materials. As widely adopted plasma sources available for thermal plasma synthesis of nanosized powders, three kinds of plasma torches, such as transferred and non-transferred DC and RF plasma torches, are introduced with the main features of each torch system. In the basis of the described torch features and the properties of suggested materials, application results including synthesis mechanism are reviewed in this paper.
THERMAL PLASMA DECOMPOSITION OF FLUORINATED GREENHOUSE GASES
Choi, Soo-Seok ; Park, Dong-Wha ; Watanabe, Takyuki ;
Nuclear Engineering and Technology, volume 44, issue 1, 2012, Pages 21~32
DOI : 10.5516/NET.77.2012.003
Fluorinated compounds mainly used in the semiconductor industry are potent greenhouse gases. Recently, thermal plasma gas scrubbers have been gradually replacing conventional burn-wet type gas scrubbers which are based on the combustion of fossil fuels because high conversion efficiency and control of byproduct generation are achievable in chemically reactive high temperature thermal plasma. Chemical equilibrium composition at high temperature and numerical analysis on a complex thermal flow in the thermal plasma decomposition system are used to predict the process of thermal decomposition of fluorinated gas. In order to increase economic feasibility of the thermal plasma decomposition process, increase of thermal efficiency of the plasma torch and enhancement of gas mixing between the thermal plasma jet and waste gas are discussed. In addition, noble thermal plasma systems to be applied in the thermal plasma gas treatment are introduced in the present paper.
PREDICTION OF THERMAL STRATIFICATION IN A U-BENT PIPE: A URANS VALIDATION
Pellegrini, M. ; Endo, H. ; Ninokata, H. ;
Nuclear Engineering and Technology, volume 44, issue 1, 2012, Pages 33~42
DOI : 10.5516/NET.02.2010.069
In the present study, CFD is employed to investigate phenomena occurring during a process of thermal stratification in U-bent pipes at transitional Reynolds number. URANS evaluation had been chosen for its low computational costs during transient analysis and for the evaluation of modeling performance in these conditions. Application of CFD at transitional Reynolds number and buoyancy driven flows indeed contains deeper uncertainties in relation to the range of applicability for hydrodynamic and thermal models. The methodology applied in the work points out, through validations with the basic problems constituting the complex stratified phenomenon, the applicability of the current turbulence modeling. Accurate predictions have been found in relation to transitional Reynolds number in bent pipes and region of stability induced by the gravitational field. On the other hand the defects introduced in the unstable region of the U bent pipe, are discussed in relation to the adopted modeling.
ANALYSIS OF THE PERMEABILITY CHARACTERISTICS ALONG ROUGH-WALLED FRACTURES USING A HOMOGENIZATION METHOD
Chae, Byung-Gon ; Choi, Jung-Hae ; Ichikawa, Yasuaki ; Seo, Yong-Seok ;
Nuclear Engineering and Technology, volume 44, issue 1, 2012, Pages 43~52
DOI : 10.5516/NET.06.2011.034
To compute a permeability coefficient along a rough fracture that takes into account the fracture geometry, this study performed detailed measurements of fracture roughness using a confocal laser scanning microscope, a quantitative analysis of roughness using a spectral analysis, and a homogenization analysis to calculate the permeability coefficient on the microand macro-scale. The homogenization analysis is a type of perturbation theory that characterizes the behavior of microscopically inhomogeneous material with a periodic boundary condition in the microstructure. Therefore, it is possible to analyze accurate permeability characteristics that are represented by the local effect of the facture geometry. The Cpermeability coefficients that are calculated using the homogenization analysis for each rough fracture model exhibit an irregular distribution and do not follow the relationship of the cubic law. This distribution suggests that the permeability characteristics strongly depend on the geometric conditions of the fractures, such as the roughness and the aperture variation. The homogenization analysis may allow us to produce more accurate results than are possible with the preexisting equations for calculating permeability.
SPATIAL AND ENERGY RESOLUTIONS OF A HEXAGONAL ANIMAL PET SCANNER BASED ON LGSO CRYSTAL AND FLAT-PANEL PMT
Lee, Chan-Mi ; Hong, Seong-Jong ; Yoon, Hyun-Suk ; Ito, Mikiko ; Kwon, Sun-Il ; Park, Sang-Keun ; Lee, Dong-Soo ; Sim, Kwang-Souk ; Lee, Jae-Sung ;
Nuclear Engineering and Technology, volume 44, issue 1, 2012, Pages 53~60
DOI : 10.5516/NET.08.2010.059
The aim of this study was to explore the spatial and energy resolutions of a PET scanner that we have recently developed. The scanner, which consists of six detector modules with 1-layer LGSO crystals, has a hexagonal configuration with a faceto- face distance of 86.4 mm between two opposite PET modules; such properties facilitate the imaging of small animals. A
point source was employed to estimate horizontal and vertical spatial resolutions. To assess the energy resolution, a uniform
cylindrical phantom was scanned. A software-based spectrum analysis of list-mode data was used to assign a local energy window centered on the photopeak position for every single crystal. For the image reconstruction, an ML-EM algorithm was used. The spatial resolutions at the center of the scanner were 0.99 mm in the horizontal direction and 1.13 mm in the vertical direction. The energy resolution averaged over each PMT ranged from 13.3%-14.3%, which gave an average value of 13.8%. These results show that this simple system is promising for small animal imaging with excellent spatial and energy resolutions.
APPLICATION OF A DUAL-ENERGY MONOCHROMATIC XRAY CT ALGORITHM TO POLYCHROMATIC X-RAY CT: A FEASIBILITY STUDY
Chang, S. ; Lee, H.K. ; Cho, G. ;
Nuclear Engineering and Technology, volume 44, issue 1, 2012, Pages 61~70
DOI : 10.5516/NET.08.2010.044
In this study, a simple post-reconstruction dual-energy computed tomography (CT) method is proposed. A dual-energy CT algorithm for monochromatic x-rays was adopted and applied to the dual-energy CT of polychromatic x-rays by assigning a representative mono-energy. The accuracy of algorithm implementation was tested with mathematical phantoms. To test the sensitivity of this algorithm to the inaccuracy of representative energy value in energy values, a simulation study was performed with mathematical phantom. To represent a polychromatic x-ray energy spectrum with a single-energy, mean energy and equivalent energy were used, and the results were compared. The feasibility of the proposed method was experimentally tested with two different micro-CTs and a test phantom made of polymethyl methacrylate (PMMA), water, and graphite. The dual-energy calculations were carried out with CT images of all possible energy pairs among 40, 50, 60, 70, and 80 kVp. The effective atomic number and the electron density values obtained from the proposed method were compared with theoretical values. The results showed that, except the errors in the effective atomic number of graphite, most of the errors were less than 10 % for both CT scanners, and for the combination of 60 kVp and 70 kVp, errors less than 6.0 % could be achieved with a Polaris 90 CT. The proposed method shows simplicity of calibration, demonstrating its practicality and feasibility for use with a general polychromatic CT.
ESTIMATION OF LOCAL LIQUID FILM THICKNESS IN TWO-PHASE ANNULAR FLOW
Lee, Bo-An ; Yun, Byong-Jo ; Kim, Kyung-Youn ; Kim, Sin ;
Nuclear Engineering and Technology, volume 44, issue 1, 2012, Pages 71~78
DOI : 10.5516/NET.02.2011.013
In many semi-empirical analyses of flow boiling heat transfer, an annular flow is often assumed as a model flow and the local liquid film thickness is a key parameter in the analysis. This work considers a simple electrical conductance technique to estimate the local liquid film thickness in two-phase annular flows. In this approach, many electrodes are mounted flush with the inner wall of the pipe. Voltage differences between two neighboring electrodes for concentric annular flows with various liquid film thicknesses are obtained before the main experiments and logged in a look-up table. For an actual application in the annual flow, voltage differences of neighboring electrodes are measured and then corresponding local film thicknesses are determined by the interpolation of the look-up table. Even though the proposed technique is quite simple and straightforward, the numerical and static phantom experiments support its usefulness.
PRELIMINARY MODELING FOR SOLUTE TRANSPORT IN A FRACTURED ZONE AT THE KOREA UNDERGROUND RESEARCH TUNNEL (KURT)
Park, Chung-Kyun ; Lee, Jae-Kwang ; Baik, Min-Hoon ; Jeong, Jong-Tae ;
Nuclear Engineering and Technology, volume 44, issue 1, 2012, Pages 79~88
DOI : 10.5516/NET.06.2011.007
Migration tests were performed with conservative tracers in a fractured zone that had a single fracture of about 2.5 m distance at the KURT. To interpret the migration of the tracers in the fractured rock, a solute transport model was developed. A two dimensional variable aperture channel model was adopted to describe the fractured path and hydrology, and a particle tracking method was used for solute transport. The simulation tried not only to develop a migration model of solutes for open flow environments but also to produce ideas for a better understanding of solute behaviours in indefinable fracture zones by comparing them to experimental results. The results of our simulations and experiments are described as elution and breakthrough curves, and are quantified by momentum analysis. The main retardation mechanism of nonsorbing tracers, including matrixdiffusion, was investigated.
AN ANALYSIS OF THE FACTORS AFFECTING THE HYDRAULIC CONDUCTIVITY AND SWELLING PRESSURE OF KYUNGJU CA-BENTONITE FOR USE AS A CLAY-BASED SEALING MATERIAL FOR A HIGH-LEVEL WASTE REPOSITORY
Cho, Won-Jin ; Lee, Jae-Owan ; Kwon, Sang-Ki ;
Nuclear Engineering and Technology, volume 44, issue 1, 2012, Pages 89~102
DOI : 10.5516/NET.06.2011.018
The buffer and backfill are important components of the engineered barrier system in a high-level waste repository, which should be constructed in a hard rock formation at a depth of several hundred meters below the ground surface. The primary function of the buffer and backfill is to seal the underground excavation as a preferred flow path for radionuclide migration from the deposited high-level waste. This study investigates the hydraulic conductivity and swelling pressure of Kyungju Ca-bentonite, which is the candidate material for the buffer and backfill in the Korean reference high-level waste disposal system. The factors that influence the hydraulic conductivity and swelling pressure of the buffer and backfill are analyzed. The factors considered are the dry density, the temperature, the sand content, the salinity and the organic carbon content. The possibility of deterioration in the sealing performance of the buffer and backfill is also assessed.