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Seo, H.,Kim, H.T.,Cha, J.E.,Bang, I.C. Pergamon Press ; Elsevier Science Ltd 2014 Annals of nuclear energy Vol.73 No.-
The moderator tank in a CANDU reactor plays a key role in the reactor core including the fuel channels and moderator. Understanding the circulation characteristics such as the flow pattern and temperature distribution in the moderator tank is important because the cooling capability is limited inside the fuel channels in the worst accident scenarios such as large break loss of coolant accident, resulting in heat removal through the Calandria tubes contacting with the fuels via thermal expansion. Therefore, measurement of the velocity profile and temperature distribution in the moderator tank is a key factor in the safety analysis of CANDU reactors because the moderator tank provides ultimate heat sink. In the present work, the velocity profile in a scaled CANDU6 moderator tank was obtained using particle image velocimetry from the 1st and 2nd jet orifices under symmetric and asymmetric flow conditions. The scaled moderator tank was prepared with acrylic, which is transparent to allow the laser penetration to create the light sheet for illuminating tracer particles. The velocity profile in the scaled moderator tank was obtained from the inlet nozzle running to the top of the tank along and near the curved wall surface and compared to a commercial CFD code, CFX.
Constrained Texture Mapping using Image Warping
Seo, H.,Cordier, F. Blackwell Publishing Ltd 2010 Computer Graphics Forum Vol.29 No.1
<P>Abstract</P><P><I>We introduce in this paper a new method for smooth foldover-free warping of images. It allows users to specify the constraints in two different ways: positional constraints to constrain the position of points in the image and gradient constraints to constrain the orientation and scaling of some parts of the image. We then show how our method is used for texture mapping with hard constraints. We start with an unconstrained planar embedding of the target mesh calculated with conventional methods. In order to obtain a mapping that satisfies the user-defined constraints, we use our warping method to align the features of the texture image with those of the unconstrained embedding. Compared to previous work, our method generates a smoother texture mapping and offers higher level of control for defining the constraints.</I></P>
Limit load analyses of helical coiled steam generator tubes with a volumetric flaw
SEO, H.‐,B.,RYU, T.‐,Y.,KIM, Y.‐,J.,CHANG, Y.‐,S.,KIM, J.‐,W.,KIM, T.‐,W. Blackwell Publishing Ltd 2012 Fatigue & fracture of engineering materials & stru Vol.35 No.11
<P><B>ABSTRACT</B></P><P>Maintaining structural integrity of piping has always been an important effort in the nuclear power industry. To resolve piping issues such as unanticipated failures caused by diverse planar and volumetric flaws, several guidelines were developed and used especially for assessment of steam generator tubes. However, because the major components of new reactors have dissimilar geometric features and loading conditions compared with those of conventional operating reactors, most of existing assessment methods are not expected to be applicable; therefore, new alternative assessment guidelines are required. In this paper, a systematic structural integrity assessment of helical coiled steam generator tubes for a small and medium modular reactor, which is currently being designed, is introduced. Three‐dimensional detailed finite element (FE) limit analyses have been carried out to simulate the behaviours of the tube containing a volumetric flaw such as elliptical wear‐type, rectangular wear‐type and tapered wear‐type defects subjected to external pressure. Failure pressures were calculated from the FE analyses by changing defect depth, defect length and defect angle affecting the load‐carrying capacity of the tube. Thereby, engineering equations were developed as a function of these key parameters to predict structural failures and system reliability to enable more reasonable design and manufacturing decisions.</P>
Seo, H.,Son, M.K.,Kim, J.K.,Choi, J.,Choi, S.,Kim, S.K.,Kim, H.J. Elsevier 2012 Photonics and nanostructures Vol.10 No.4
Dye-sensitized solar cells (DSCs) have been proposed as a substitute for silicon crystalline solar cells which have a high manufacturing cost but it is still difficult to fabricate highly efficient DSC module assemblies. Therefore, in this work, an externally connected module assembly was investigated for industrial applications of DSCs. The equivalent circuit of a DSC was determined using typical electrical components and the cause of a current loss in the parallel connection was analyzed using electrochemical impedance spectroscopy. Also, an externally connected module has been constructed using 50 DSCs, where each cell has an active area of 8cm<SUP>2</SUP> (4.62cmx1.73cm) and a conversion efficiency of 4.21% under 1 sun illumination (P<SUB>in</SUB> of 100mW/cm<SUP>2</SUP>). As a result, the externally connected DSC module assembly has an output of 7.4V and 200mA, and shows stable performance, with an energy conversion efficiency of 4.44% under 0.45 sun illuminations.
Highly selective fluorescent probe for sequential recognition of copper(II) and iodide ions
Seo, H.,An, M.,Kim, B.Y.,Choi, J.H.,Helal, A.,Kim, H.S. Pergamon Press 2017 Tetrahedron Vol.73 No.31
A new highly selective fluorescent probe based on 2-(2'-aminolphenyl)-4-hydroxymethylthiazole (1) was developed for the detection of copper and iodide ions in ethanol. Probe 1 selectively detected Cu<SUP>2+</SUP> through a ''switch off'' response, showing a good association constant (K<SUB>a</SUB> = 1.43 x 10<SUP>5</SUP> M<SUP>-1</SUP>) and binding with Cu<SUP>2+</SUP> ions in a 1:1 stoichiometry. An in situ generated 1-Cu<SUP>2+</SUP> (1:1) ensemble detected I<SUP>-</SUP> ions sequentially through a ''switch on'' response. The ''switch off'' response occurred with selective complexation of Cu<SUP>2+</SUP> ions due to intramolecular charge transfer (ICT). An ensemble of 1 and copper(II) showed higher selectivity towards iodide than towards any other anions due to the reduction of Cu<SUP>2+</SUP> to Cu<SUP>+</SUP> by I<SUP>-</SUP> and subsequent complexation with 1.
Subchannel analysis of a small ultra-long cycle fast reactor core
Seo, H.,Kim, J.H.,Bang, I.C. North-Holland Pub. Co 2014 Nuclear engineering and design Vol.270 No.-
Thermal-hydraulic evaluation of a small ultra-long cycle fast reactor (UCFR) core is performed based on existing safety regulations. The UCFR is an innovative reactor newly designed with long-life core based on the breed-and-burn strategy and has a target electric power of 100MWe (UCFR-100). Low enriched uranium (LEU) located at the bottom region of the core play the role of igniter to operate the UCFR for 60 years without refueling. A metallic form is selected as a burning fuel region material after the LEU location. HT-9 and sodium are used as cladding and coolant materials, respectively. In the present study, MATRA-LMR, subchannel analysis code, is used for evaluating the safety design limit of the UCFR-100 in terms of fuel, cladding, and coolant temperature distributions in the core as design criteria of a general fast reactor. The start-up period (0 year of operation), the middle of operating period (30 years of operation), and the end of operating cycle (60 years of operation) are analyzed and evaluated. The maximum cladding surface temperature (MCST) at the BOC (beginning of core life) is 498<SUP>o</SUP>C on average and 551<SUP>o</SUP>C when considering peaking factor, while the MCST at the MOC (middle of core life) is 498<SUP>o</SUP>C on average and 548<SUP>o</SUP>C in the hot channel, respectively, and the MCST at the EOC (end of core life) is 499<SUP>o</SUP>C on average and 538<SUP>o</SUP>C in the hot channel, respectively. The maximum cladding surface temperature over the long cycle is found at the BOC due to its high peaking factor. It is found that all results including fuel rods, cladding, and coolant exit temperature are below the safety limit of general SFR design criteria.