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.

CMOS depth sensor with programmable filter circuits for environment-adaptive noise suppression

Seo, H.,Kim, B.,Chun, J.-H.,Kim, S.-J.,Choi, J. Institution of Electrical Engineers 2018 Electronics letters Vol.54 No.19

Crack Detection in Pillars Using Infrared Thermographic Imaging

Seo, H.,Choi, H.,Park, J.,Park, J.,Lee, I.-M. ASTM International 2017 Geotechnical testing journal Vol.40 No.3

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.

Histogram-based mixed-signal time-to-digital-converter array for direct time-of-flight depth sensors

Seo, H.,Choi, J. Institution of Electrical Engineers 2019 Electronics letters Vol.55 No.6

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.

Development of prototype induced-fission-based Pu accountancy instrument for safeguards applications

Seo, H.,Lee, S.K.,An, S.J.,Park, S.H.,Ku, J.H.,Menlove, H.O.,Rael, C.D.,LaFleur, A.M.,Browne, M.C. Pergamon Press 2016 Applied radiation and isotopes Vol.115 No.-

Prototype safeguards instrument for nuclear material accountancy (NMA) of uranium/transuranic (U/TRU) products that could be produced in a future advanced PWR fuel processing facility has been developed and characterized. This is a new, hybrid neutron measurement system based on fast neutron energy multiplication (FNEM) and passive neutron albedo reactivity (PNAR) methods. The FNEM method is sensitive to the induced fission rate by fast neutrons, while the PNAR method is sensitive to the induced fission rate by thermal neutrons in the sample to be measured. The induced fission rate is proportional to the total amount of fissile material, especially plutonium (Pu), in the U/TRU product; hence, the Pu amount can be calibrated as a function of the induced fission rate, which can be measured using either the FNEM or PNAR method. In the present study, the prototype system was built using six <SUP>3</SUP>He tubes, and its performance was evaluated for various detector parameters including high-voltage (HV) plateau, efficiency profiles, dead time, and stability. The system's capability to measure the difference in the average neutron energy for the FNEM signature also was evaluated, using AmLi, PuBe, <SUP>252</SUP>Cf, as well as four Pu-oxide sources each with a different impurity (Al, F, Mg, and B) and producing (α,n) neutrons with different average energies. Future work will measure the hybrid signature (i.e., FNEMxPNAR) for a Pu source with an external interrogating neutron source after enlarging the cavity size of the prototype system to accommodate a large-size Pu source (~600g Pu).

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>

Analysis of current loss from a series-parallel combination of dye-sensitized solar cells using electrochemical impedance spectroscopy

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.

Capacity Region of Multiuser Shared Channel with Time-Varying Transmission Power

Seo, H.,Park, D.,Lee, B.G. IEEE INSTITUTE OF ELECTRICAL AND ELECTRONICS 2009 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.57 No.8