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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>
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>
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.
Optimization of hybrid-type instrumentation for Pu accountancy of U/TRU ingot in pyroprocessing
Seo, H.,Won, B.H.,Ahn, S.K.,Lee, S.K.,Park, S.H.,Park, G.I.,Menlove, S.H. Pergamon Press 2016 Applied radiation and isotopes Vol.108 No.-
One of the final products of pyroprocessing for spent nuclear fuel recycling is a U/TRU ingot consisting of rare earth (RE), uranium (U), and transuranic (TRU) elements. The amounts of nuclear materials in a U/TRU ingot must be measured as precisely as possible in order to secure the safeguardability of a pyroprocessing facility, as it contains the most amount of Pu among spent nuclear fuels. In this paper, we propose a new nuclear material accountancy method for measurement of Pu mass in a U/TRU ingot. This is a hybrid system combining two techniques, based on measurement of neutrons from both (1) fast- and (2) thermal-neutron-induced fission events. In technique #1, the change in the average neutron energy is a signature that is determined using the so-called ring ratio method, according to which two detector rings are positioned close to and far from the sample, respectively, to measure the increase of the average neutron energy due to the increased number of fast-neutron-induced fission events and, in turn, the Pu mass in the ingot. We call this technique, fast-neutron energy multiplication (FNEM). In technique #2, which is well known as Passive Neutron Albedo Reactivity (PNAR), a neutron population's changes resulting from thermal-neutron-induced fission events due to the presence or absence of a cadmium (Cd) liner in the sample's cavity wall, and reflected in the Cd ratio, is the signature that is measured. In the present study, it was considered that the use of a hybrid, FNEMxPNAR technique would significantly enhance the signature of a Pu mass. Therefore, the performance of such a system was investigated for different detector parameters in order to determine the optimal geometry. The performance was additionally evaluated by MCNP6 Monte Carlo simulations for different U/TRU compositions reflecting different burnups (BU), initial enrichments (IE), and cooling times (CT) to estimate its performance in real situations.
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.
Long-range enhancers modulate Foxf1 transcription in blood vessels of pulmonary vascular network
Seo, H.,Kim, J.,Park, G. H.,Kim, Y.,Cho, S. W. Springer Science + Business Media 2016 Histochemistry and cell biology Vol.146 No.3
<P>Intimate crosstalk occurs between the pulmonary epithelium and the vascular network during lung development. The transcription factor forkhead box f1 (Foxf1) is expressed in the lung mesenchyme and plays an indispensable role in pulmonary angiogenesis. Sonic hedgehog (Shh), a signalling molecule, is expressed in lung epithelium and is required to establish proper angiogenesis. It has been suggested that Foxf1, a downstream target of the Shh signalling pathway, mediates interaction between angiogenesis and the epithelium in lung. However, there has been no clear evidence showing the mechanism how Foxf1 is regulated by Shh signalling pathway during lung development. In this study, we investigated the lung-specific enhancers of Foxf1 and the Gli binding on the enhancers. At first, we found three evolutionarily conserved Foxf1 enhancers, two of which were long-range enhancers. Of the long-range enhancers, one demonstrated tissue-specific activity in the proximal and distal pulmonary blood vessels, while the other one demonstrated activity only in distal blood vessels. At analogous positions in human, these long-range enhancers were included in a regulatory region that was reportedly repeatedly deleted in alveolar capillary dysplasia with misalignment of pulmonary vein patients, which indicates the importance of these enhancers in pulmonary blood vessel formation. We also determined that Gli increased the activity of one of these long-range enhancers, which was specific to distal blood vessel, suggesting that Shh regulates Foxf1 transcription in pulmonary distal blood vessel formation.</P>