• Nuclear Engineering and Technology
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• v.46 no.4
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• pp.521-528
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• 2014

The surface modification of engineering materials by laser beam scanning (LBS) allows the improvement of properties in terms of reduced wear, increased corrosion resistance, and better strength. In this study, the laser beam scan method was applied to produce an oxide dispersion strengthened (ODS) structure on a zirconium metal surface. A recrystallized Zircaloy-4 alloy sheet with a thickness of 2 mm, and $Y_2O_3$ particles of $10{\mu}m$ were selected for ODS treatment using LBS. Through the LBS method, the $Y_2O_3$ particles were dispersed in the Zircaloy-4 sheet surface at a thickness of 0.4 mm, which was about 20% when compared to the initial sheet thickness. The mean size of the dispersive particles was 20 nm, and the yield strength of the ODS treated plate at $500^{\circ}C$ was increased more than 65 % when compared to the initial state. This strength increase was caused by dispersive $Y_2O_3$ particles in the matrix and the martensite transformation of Zircaloy-4 matrix by the LBS.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.6
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• pp.457-465
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• 2018

Since IMO has discussed the effectuation of the EEDI, EEOI and SEEMP, each country, shipping company, shipbuilding company and research institute have been requested to prepare the design, construction and operation of the efficient ship. From the shipbuilding company's point of view, it was necessary to develop a method based on the maneuvering equations of motion in a bid to estimate the EEOI considering the design, model test results and the calculation results of the ship. In this paper, the estimation method of RPM, power and fuel consumption proposed in the previous research was developed to construct a framework that helps in the estimation of the EEOI. It was possible to estimate the EEOI from the estimated ship speed (distance), LNG cargo mass, fuel consumptions and emission factors according to the type of fuel. The rapid increase of the evaluated EEOI was observed when the LNGC with ME-GI engine executing the course changed with a large difference. This prompted the comparison of the type of fuel on the estimated EEOI by considering HFO, LNG fuel and MGO properties.

• Korean Journal of Materials Research
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• v.29 no.8
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• pp.483-490
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• 2019

Currently, the Korean nuclear industry uses ZIRLO as material for nuclear fuel cladding(zirconium alloy). KEPCO Nuclear Fuel is in the process of developing a HANA alloy to enable domestic production of cladding. Cladding manufacture involves multistage heat treatments and pickling processes, the latter of which is vital for the removal of defects and impurities on the cladding surface. SMUT that forms on the cladding surface during such pickling process is a source of surface defects during heat treatment and post-treatment processes if not removed. This study analyzes ZIRLO, HANA-4, and HANA-6 alloy claddings to extensively study the SEM/EDS, XRD, and particle size characteristics of SMUT, which are second phase particles that are formed on the cladding surface during pickling processes. Using the analysis results, this study observes SMUT formation characteristics according to Nb concentration in Zr alloys during the washing process following the pickling process. In addition, this study observes SMUT removal characteristics on cladding surfaces according to concentrations of nitric acid and hydrofluoric acid in the acid solution.

• Journal of Energy Engineering
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• v.3 no.2
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• pp.130-150
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• 1994

Coal-water mixture(CWM) fuel has attracted much attention as a substitute fuel for oil by which high economics and short-term commercialization might be realized in comparison with other coal conversion technologies. There are many factors that affect the CWM combustibility, such as the physical properties of CWM, the performance of atomizer and burner, operating conditions, capacity and load of the boiler, etc. Particularly, atomization quality is extremely critical to achieving acceptable carbon conversion efficiency of CWM fuel and maintaining the flame stability, because the coal particles in the CWM droplets burn as agglomerates. This paper presents the R&D results about the CWM atomization characteristics, including the significance of CWM atomization the R&D results about the CWM atomization characteristics, including the significance of CWM atomization quality, the atomization and combustion mechanism, the type of CWM atomizer, size and size distribution of CWM droplets and some factors that influence the atomization performance.

• Proceedings of the Korean Professional Engineer Association Conference
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• 1984.12a
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• pp.84-91
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• 1984

Heavy Residual Fuel oils is a mixture of reduced crude from crude unit, bottom products from vacuum and/or catalytic cracking unit with distillate to meet the specification and generally used as Heavy Fuel Oil for large combustion engines, boilers, etc…. But this study was made to investigate Heavy Residual Fuel oils for using as industrial raw material and resulted the following possibilties as valuable raw material as well as Heavy Fuel Oil. 1) Production of straight asphalt through vacuum distillation unit. 2) Using straight asphalt from vacuum distillation unit for manufacturing of Blown Asphalts, Cut Back Asphalts, Emulsified Asphalts and Asphalt Compound, etc…. 3) Using waxy oil side streams for manufacturing of raw oil to be Lube Oil base stocks through solvent dewaxing. 4) Production of lube base oils from dewaxed raw oil through chemical treatments. 5) Manufacturing of paraffine wax from slack wax to be produced as by product of dewaxing process.

• Macromolecular Research
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• v.15 no.4
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• pp.379-384
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• 2007

Sulfonation of polyetheretherketones (PEEK) was carried out in order to fabricate commercial perfluorosulfonic acid membrane alternatives, which were characterized in terms of their ion exchange capacity, ionic conductivity, water swelling, methanol crossover and electrochemical performance in their direct application as a methanol fuel cell. A high ion exchange capacity, 1.88, was achieved with a sulfonation reaction time of 8 h, with a significantly low methanol crossover low compared to that of Nafion. However, the morphological stability was found to deteriorate for membranes with sulfonation reaction times exceeding 8 h. Electrochemical cell tests suggested that the fabrication parameters of the membrane electrode assembly based on the sulfonated PEEK membranes should be optimized with respect to the physicochemical properties of the newly prepared membranes.

• Nuclear Engineering and Technology
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• v.41 no.8
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• pp.1087-1100
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• 2009

A finite element method utilizing the Galerkin form of the weighted residuals procedure was developed to estimate the mechanical behavior for a coated fuel particle (CFP) of a high temperature gas-cooled reactor (HTGR). Through a weak formulation, finite element equations for multiple layers were set up to calculate the displacements and stresses in a CFP. The finite element method was applied to the stress analyses for three coating layers of a tri-isotropic coated fuel particle (TRISO) of a HTGR. The stresses calculated by the finite element method were in good agreement with those from a previously developed computer code and depicted the typical stress behavior of the coating layers very well. The newly developed finite element method performs a stress analysis for multiple bonded layers in a CFP by changing the material properties at any position in the layers during irradiation.

• Nuclear Engineering and Technology
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• v.52 no.8
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• pp.1724-1731
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• 2020

Low cycle fatigue tests on the hydrogenated welding seam of Zr-Sn-Nb alloy at room temperature and 360 ℃ had been carried out by using the funnel-shaped flat specimens. The relationships between nominal stress & strain directly measured across the funnel and local stress & strain at the root of the funnel are given by considering cyclic plasticity correction. The results show that the fatigue resistance of welding seam at room temperature is only slightly better than that at 360 ℃. Probabilistic fatigue life curves are obtained by using a two-parameter power function.

• Journal of the Korean Ceramic Society
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• v.33 no.6
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• pp.631-636
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• 1996

The powder characteristics of UO2 via AUC prepared by precipitation from a UN with AC soiution produced from nuclear fuel powder conversion plant and that of the existing facility were compared. Mean particle size of AUC powder was decreased and agglomerates were much occured in case of using the AC solution that that of the gases but other properties such as particle size distribution and shape of particle are thought to be similarly. In compaction of UO2 powder the breaking pressur of agglomerated UO2 powder and the sintered density of final UO2 pellet from AC solution were measured 1.45$\times$108 N/m2 and 10.52 g/cc, These values could be used in nuclear fuel powder fabrication process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.651-654
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• 2001

In the dismantling process of nuclear spent fuels, the spent fuel rod cutting process, followed immediately by the decladding process, performs the cutting the spent fuel rods to a proper length for fast decladding operation. In this paper, we analyzed the chemical compositions, mechanical properties, and physical characteristics for SUS and zircaloy tubes in order to identify the feasibility of cutter-blade type in cutting SUS and zircaloy tubes. It is considered that material, shape and angle, and heat treatment for fabricating the highly durable cutter blade and also it is investigated that the round-shape sustenance of cross-section, amount of debris production, and fire occurrence for measuring the cutting performance on SUS and zircaloy tubes, spent fuel rod cutting device is designed to be operated automatically through the remote control system for use in Hot Cell(radioactive) area and the electro-driven mechanical parts are modularized for easy maintenance. Results from various experiments confirm the efficiency of this device.