Estimation of Operational Stability for the KSTAR TF Magnet

Chu, Y,Kim, Y O,Yonekawa, H,Park, S H,Lee, H J,Kim, K P,Park, K R,Na, H K IEEE 2011 IEEE transactions on applied superconductivity Vol.21 No.3

<P>During the operation of the Korea Superconducting Tokamak Advanced Research (KSTAR), there exist various disturbances that cause the conductors to become unstable. The KSTAR Toroidal Magnet (TF) system was designed to secure the sufficient stability against them. The stability analysis showed that the energy margin of the TF Cable-In-Conduit (CIC) conductor was sufficiently high so that the expected disturbances could not cause the conductor to quench. During the 2nd KSTAR campaign in 2009, the cryogenic stability of the TF magnet system was analysed by energizing it up to 36 kA that is a bit higher than the designed current of 35.2 kA. The temperature increase measured at helium outlets was less than 0.1 K, which was well consistent with the analysis. Even in the reference plasma scenario, it was expected from the analysis that there still exists the sufficient temperature margin more than 4 K. The quench analysis was carried out to validate the design of the present TF CIC conductor from the magnet protection's point of view. In this paper, the cryogenic stability of the TF magnet system was estimated and the quench detection parameters were derived for protecting possible damages from quenches.</P>

Quench Simulation and Detection in KSTAR PF Magnet System

Chu, Y,Park, S H,Yonekawa, H,Kim, Y O,Lee, H J,Kim, K P,Lee, S J,Park, K R,Oh, Y K,Na, H K IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3

<P>To detect quenches in the Poloidal Field (PF) magnet system is more difficult than the Toroidal Field (TF) magnet system due to excessively high inductive voltages generated by PF pulse-currents and plasma currents. According to reference scenarios being considered so far, the maximum voltage across the PF coils is inductively generated up to about 3.5 kV during the start of plasma (SoP) stage in a very short time period. The voltage measured by compensation of the inductive voltage should be below a certain level which is called as the quench voltage threshold. However, the compensated voltage might be higher than the threshold even with the well-designed compensation schemes. Accordingly, the quench voltage threshold and the quench protection delay time should be properly determined for the quench detection not to take a false action which could cause the fast energy discharge. From the quench simulation using the calculation of hot spot temperature and the resistive voltage growth as a function of time, the proper values of the quench detection parameters of the PF magnet system were derived for the maximum hot temperature rise to be limited within 150 K.</P>

Separation dynamics of hydrogen isotope gas in mesoporous and microporous adsorbent beds at 77 K: SBA-15 and zeolites 5A, Y, 10X

Chu, X.Z.,Cheng, Z.P.,Xiang, X.X.,Xu, J.M.,Zhao, Y.J.,Zhang, W.G.,Lv, J.S.,Zhou, Y.P.,Zhou, L.,Moon, D.K.,Lee, C.H. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.9

The separation of a hydrogen isotope mixture on porous materials was studied using equilibrium and breakthrough experiments. The adsorption equilibria of H<SUB>2</SUB> and D<SUB>2</SUB> on SBA-15 with mesopores and molecular sieves 5A, Y, and 10X with micropores were measured at 77 K using the volumetric method. The breakthrough experiments of a H<SUB>2</SUB> and D<SUB>2</SUB> mixture in each adsorbent bed were carried out at various conditions of flow rate and pressure. The equilibrium ratio of D<SUB>2</SUB> to H<SUB>2</SUB> on mesoporous molecular sieves was larger than the ratio on microporous molecular sieves (SBA-15 > 10X > Y > 5A), but the difference among the adsorbents decreased with increases in pressure. On the other hand, the order of breakthrough separation factor showed the opposite result (SBA-15 < 10X < Y < 5A). The breakthrough separation factors for zeolite 10X was approximately equal to the equilibrium ratio of D<SUB>2</SUB> to H<SUB>2</SUB> at the corresponding partial pressures, whereas zeolites 5A and Y showed higher breakthrough separation factors than their equilibrium ratios. In SBA-15, the separation factors from breakthrough results were even smaller than the corresponding equilibrium ratio. In the microporous adsorbent with a limited pore size (zeolite 5A in the study), the diffusion mechanism contributed to the separation of hydrogen isotope gases as one of key factors.

Listeria monocytogenes에 의한 신생아 감염증 4례

송필준,주정혜,민정식,이규환,유신애,안창일 慶熙大學校 醫科大學 1982 慶熙 醫大 論文集 Vol.7 No.1

이비인후과 의뢰환자의 임상통계적 고찰

천표,장병일,추광철,김선곤 대한이비인후과학회 1977 대한이비인후과학회지 두경부외과학 Vol.20 No.4

Hydraulic Behavior of Rectangular Cable-In-Conduit Conductor for KSTAR Superconducting Magnet System

Park, S H,Chu, Y,Yonekawa, H,Kim, Y O,Kim, K P,Woo, I S,Han, W S,Hong, J S,Park, K R,Na, H K,Kwon, M IEEE 2011 IEEE transactions on applied superconductivity Vol.21 No.3

<P>The Korea Superconducting Tokamak Advanced Research (KSTAR) adopted superconducting coils which consist of rectangular cable-in-conduit conductors (CICC) without a central hole for supercritical helium. Most of all, the KSTAR has a unique superconducting magnet system with Nb<SUB>3</SUB>Sn and NbTi such as ITER. We expect that the test results of KSTAR experiments can also provide useful information for ITER and the other fusion devices. Up to now, the KSTAR superconducting magnet system is showing a larger flexibility and reliability in operation. For example, the TF magnet system has achieved the current charging of 36.2 kA and PF magnet system has been also charged up to ±4 kA without difficulties during the last two times KSTAR campaigns. The significant thermo-hydraulic characteristics such as helium flow distribution, pressure drop between the inlet and outlet of coil, the friction factor and the temperature variation according to the current charging operations are introduced in this paper.</P>

Mechanical properties of MgO–Al₂O₃–SiO₂ glass-infiltrated Al₂O₃–ZrO₂ composite

Balakrishnan, A.,Panigrahi, B.B.,Sanosh, K.P.,Chu, Min-Cheol,Kim, T.N.,Cho, Seong-Jai Elsevier 2009 Journal of materials processing technology Vol. No.

<P><B>Abstract</B></P><P>This work attempts to improve the mechanical properties of alumina-10wt% zirconia (3mol% yttria stabilized) composite by infiltrating a glass (magnesium aluminum silicate glass) of lower thermal expansion on the surface at high temperature. The glass improved the strength of the composite at room temperature as well as at higher temperatures. There was a significant improvement in the Weibull modulus after the glass infiltration. Glass-infiltrated samples showed better thermal shock resistance. The magnitude of strength increment was found to be in the order of the surface residual stress generated by thermo-elastic properties mismatch between the composite and the infiltrated glass.</P>

Key Features in the Operation of KSTAR

Jong-Gu Kwak,Oh, Y. K.,Kim, K. P.,Kim, S. W.,Hong, S. H.,Chu, Y.,Lee, H. J.,Kim, Y. O.,Kim, J.,Park, S. L.,Hahn, S. H.,Park, M. K.,Kim, H. K.,Bak, J. G.,Bae, Y. S.,Ko, W. H.,Lee, S. G.,Lee, J. H.,Jung IEEE 2012 IEEE transactions on plasma science Vol.40 No.3

<P>The Korea Superconducting Tokamak Advanced Research (KSTAR) device is aimed at advanced tokamak (AT) research. Three years have passed since it achieved its first plasma in 2008. Because it is a superconducting machine and is working toward AT research, it has unique features in terms of the machine engineering and operation. The toroidal field (TF) magnet coils are made of Nb<SUB>3</SUB>Sn, which provide high TFs up to 3.5 T, and have been fully tested. The poloidal field (PF) magnet coils, consisting of both Nb<SUB>3</SUB>Sn and NbTi, which have a maximum current of 25 kA in their design, were tested up to 15 kA. A thermal hydraulic analysis is being conducted for PF magnet coil operation. All plasma-facing components (PFCs) are equipped with water cooled graphite tiles and have the capability of being baked up to 350°C. A startup scenario, which considered both the effect of the ferromagnetic material in the cable in conduit conductor jacket of the magnet coils as well as a nonferromagnetic up-down asymmetry in the cryostat structure, was developed and demonstrated its effectiveness by the last two year's reliable operations. Passive stabilizers and in-vessel control coils (IVCCs) are key components to realize AT operation in KSTAR. The segmented IVCC coils were connected to form circular coils for internal vertical control in 2010, and diverted plasmas with high elongation (κ~1.8, δ>;0.6) were achieved. A neutral beam injection (NBI) system was developed aiming at 2 MW, 300 s per ion source which meets the long-pulse requirement of KSTAR. An NBI ion source with a power of 1.7 MW at 100 kV has been commissioned for 10 s. Finally, ELMy H-modes were successfully produced with 1.3-MW NBI power at a plasma current of 0.6 MA in the 2010 campaign. The first H-mode discharge (#4200) in KSTAR was achieved one year earlier than officially planned and was done at B<SUB>T</SUB> = 2 T with I<SUB>p</SUB> = 0.6 MA in a well-balanced double null configuration after boronization on the PFC. Successful operations in the early days of KSTAR including H-mode experiments revealed the capability of advanced and steady-state operation which is essential for the international thermonuclear experimental reactor (ITER) and future fusion reactors.</P>

Biosynthesis of a novel fisetin glycoside from engineered Escherichia coli

Pandey, R.P.,Parajuli, P.,Chu, L.L.,Kim, S.Y.,Sohng, J.K. Korean Society of Industrial and Engineering Chemi 2016 Journal of industrial and engineering chemistry Vol.43 No.-

<P>Escherichia coli BL21(DE3)/Delta pgi Delta zwf Delta galU mutant was engineered by overexpressing thymidine diphosphate (dTDP)-D-glucose synthase (tgs), dTDP-D-glucose 4,6-dehydratase (dh), and a sugar aminotransferase (wecE) from different sources to produce a pool of dTDP-4-amino-4,6-dideoxy-D-galactose in the cell cytosol. To this recombinant mutant, two Arabidopsis thaliana glycosyltransferases (ArGT-3 and ArGT-4) were overexpressed to generate two glycosylation platforms (E. coli BL21(DE3)/ Delta pgi Delta zwf Delta galUTDW-3 and E. coli BL21(DE3)/Delta pgi Delta zwf Delta galUTDW-4), which were accessed for the glycosylation of fisetin. As a result, one of the two systems, E. coli BL21(DE3)/Delta pgi Delta zwf Delta galUTDW-3, was able to conjugate 4-amino-4,6-dideoxy-D-galactose sugar at the 3-OH position of fisetin, producing an unnatural fisetin 3-O-4-amino-4,6-dideoxy-D-galactoside. (C) 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.</P>

Status of the KSTAR superconducting magnet system development

Kim, K.,Park, H.K.,Park, K.R.,Lim, B.S.,Lee, S.I.,Chu, Y.,Chung, W.H.,Oh, Y.K.,Baek, S.H.,Lee, S.J.,Yonekawa, H.,Kim, J.S.,Kim, C.S.,Choi, J.Y.,Chang, Y.B.,Park, S.H.,Kim, D.J.,Song, N.H.,Kim, K.P.,So International Atomic Energy Agency 2005 Nuclear fusion Vol.45 No.8

<P>The aim of the Korea superconducting tokamak advanced research (KSTAR) project is to develop a steady-state-capable advanced superconducting tokamak for establishing a scientific and technological basis for an attractive fusion reactor. Since the KSTAR mission includes the achievement of a steady-state-capable operation, the use of superconducting coils is an obvious choice for the magnet system. The KSTAR superconducting magnet system consists of 16 toroidal field (TF) and 14 poloidal field (PF) coils which include 8 central solenoid coils. Both the TF and PF coil systems use internally-cooled cable-in-conduit conductors (CICC). The TF coil system provides a magnetic field of 3.5 T at the plasma centre and the PF coil system provide a flux swing of 17 V s. The major achievement in the KSTAR magnet system development includes the development of CICC, a full size TF model coil, a background magnetic field generation coil system and the construction of a large scale superconducting magnet and the CICC test facility. TF and PF coils are at the stage of fabrication for the KSTAR completion in the year 2007.</P>