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Study on the endoscopic inspection of ITER thermal shield cooling pipes
Nam, Kwanwoo,Her, Namil,Park, Won Woo,Won, Jong Moon,Kim, Il Jin,Kang, Youngkil,Kang, Dong Kwon Elsevier 2019 Fusion engineering and design Vol.146 No.2
<P><B>Abstract</B></P> <P>A novel endoscope is developed for the inspection of long and complex-shaped cooling pipe of ITER Thermal Shield (TS). The mechanical design of the endoscope is improved for its easier insertion into long pipe routing. Main break-through is to reduce the cable friction against metal pipe surface as well as to maintain the elastic rigidity of the cable for the insertion. Spacers are attached on both the camera head and the cable to reduce the friction. Plate spring tube is used to protect signal wire and to maintain elastic rigidity of the cable. The conceived endoscope was tested to the pipe routing mock-up, which is similar to the longest and most complex TS pipe routing. Special device is also presented for making the endoscope insertion be easier. The insertion test result is compared with that of a conventional endoscope. Several endoscopic images are also discussed for typical pipe samples and for the curved region of pipe routing.</P>
Flow analysis and test for ITER thermal shield components
Nam, Kwanwoo,Lim, Kisuk,Kang, Dongkwon Elsevier 2018 Fusion engineering and design Vol.136 No.1
<P><B>Abstract</B></P> <P>Flow distribution on the piping network of ITER Thermal Shield (TS) is analyzed and orifice installation is suggested for attenuating flow mal-distribution. Flow test is performed for a TS segment to verify the analysis model. Room temperature nitrogen gas passes through the cooling pipe on TS segment with test flow rate which is equivalent to the actual operating condition of TS. Flow rate is controlled by a thermal mass flow controller and pressure drop between the inlet and the outlet of the pipe routing is measured by a differential pressure gauge. Test result is compared with the analysis one to check the validity of the analysis model for the real manufactured TS segment. The flow test is also conducted for the fabricated orifices. The loss coefficient of the orifice is compared with that used in the analysis. The loss coefficient correlation for the fabricated orifices is obtained from the test results.</P>
Thermal and Electrical Analysis of Coated Conductor Under AC Over-Current
Kwanwoo Nam,Chanjoo Lee,Dong Keun Park,Tae Kuk Ko,Bok-Yeol Seok IEEE 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>In order to design a high temperature superconducting (HTS) winding for the fault current limiter (FCL), the resistance and the temperature of the winding should be calculated quantitatively under the over-current caused by fault condition. In this paper, a transient analysis is performed to estimate the resistance development and the temperature rise of coated conductor (CC) under AC over-current. A one-dimensional thermal conduction model with an electrical circuit model is developed for the solenoid coil configuration at 65 K cooling condition. All the composite materials except the buffer layer in CC are considered in the model. Two kinds of stabilizer materials (copper/stainless steel) are considered to investigate the current limitation of CC. The simulation results are compared with the experimental data of the commercial CC. The effect of Ag and solder layer on the simulation result are revealed for CC.</P>
Manufacturing study of lower cryostat thermal shield cylinder component for ITER tokamak
Nam, Kwanwoo,Her, Namil,Hur, Junyoung,Park, Won Woo,Kang, Kyoung-O,Lim, Kisuk,Kim, Il Jin,Kang, Youngkil,Arzoumanian, Terenig,Panchal, Manoj,Pichel, German Perez,Noh, Chang Hyun,Kang, Dong Kwon Elsevier 2019 Fusion engineering and design Vol.146 No.1
<P><B>Abstract</B></P> <P>This paper describes the manufacturing study of ITER Lower Cryostat Thermal Shield (LCTS) cylinder components, which are to be delivered to ITER site. All LCTS cylinder 20 ° sectors will be assembled at the ITER site by the flange joints, which are welded to the shells. Reliability of cooling pipe welding was checked by two inspection methods: endoscopy and vacuum leak test. Pre-assembly of three 20 ° sectors is one of the important step to ensure dimensional tolerance and its process is described in details. Dimensions of the pre-assembled 60 ° sector was measured by a laser tracker. The qualification of silver coating facility was carried out using a simple well-defined plate mock-up. After the facility qualification, silver coating of LCTS cylinder 20 ° sectors had been conducted. Technical efforts to improve the coated surface quality are presented in this paper.</P>
조해용(Haeyong Cho),김관우(Kwanwoo Kim),남기정(Gijeong Nam),이제훈(Jaehoon Lee),서정(Jeong Suh) 한국레이저가공학회 2006 한국레이저가공학회지 Vol.9 No.1
Glass is one of brittle materials. Generally, brittle material is weak for tensile stress but strong for compression stress. Laser breaking of glass used this brittle characteristics. Laser breaking of glass was simulated to optimize breaking condition by using commercial FEM code MARC which is applicable to thermo-mechanical coupling analysis. Various shapes of heat sources were applied to the analysis and the distance between heating and cooling source were varied for each simulation. The shapes of heat sources were circle, single and double ellipse and the distance was varied from 0㎜ to 30㎜. Moving heat sources were designed on the basis of experimental condition. As a result, double elliptic shape of heat source was the most suitable among them in laser breaking of glass. And it should be useful to determine optimal condition of laser breaking for glass.
Development of a 13.2 kV/630 A (8.3 MVA) High Temperature Superconducting Fault Current Limiter
Hyoungku Kang,Chanjoo Lee,Kwanwoo Nam,Yong Soo Yoon,Ho-Myung Chang,Tae Kuk Ko,Bok-Yeol Seok IEEE 2008 IEEE transactions on applied superconductivity Vol.18 No.2
<P>This paper deals with fabrication and development of a high temperature superconducting (HTS) fault current limiter (FCL) based on YBCO coated conductor (CC) wire for distribution systems. The capacity of the developed HTS FCL is 8.3 MVA and its rated voltage is 13.2 kV which corresponds to a three-phase power equipment voltage class of 22.9 kV. Tests of the developed prototype HTS FCL were conducted at Korea Electrotechnology Research Institute (KERI) accredited as a testing laboratory by the Korea Laboratory Accreditation Scheme (KOLAS). A short-circuit test and an AC dielectric withstand voltage test for the HTS FCL were conducted under sub-cooled liquid nitrogen (LN<SUB>2</SUB> ) conditions of 3 bar and 65 K. The magnitude of an asymmetric short- circuit current without FCL reached 30 kA<SUB>peak</SUB> in a short-circuit test. The superconducting coil quenched instantaneously after the fault, and the magnitude of the fault current was limited to 3.6 kA<SUB>peak</SUB> within quarter cycle by the developed resistance of the superconducting coil. An AC dielectric withstand voltage test was performed, and the HTS FCL successfully withstood 143 kV for 1 minute. Also, it was found that there was no electrical or mechanical damage on the superconducting coil after the tests.</P>
Structural Analysis of the ITER Thermal Shield for Final Design Verification
Chang Hyun Noh,Kwanwoo Nam,Woo Ho Chung,Dong Kwon Kang,Kyoung-O Kang,Hee Jae Ahn,Her, Nam I.,Hamlyn-Harris, Craig Institute of Electrical and Electronics Engineers 2014 IEEE transactions on plasma science Vol. No.
<P>The structural integrity of the ITER thermal shield (TS) has been verified by structural analysis. In this paper, the analysis process methodology and demonstration of the structural integrity for the TS are described. The analysis is performed for the TS global models and detailed models, such as supports and joints. TS joints in the shell model are modeled using orthotropic material properties. To verify the structural reliability for the TS, plastic collapse, buckling, ratcheting, and fatigue are assessed in accordance with ASME Section VIII, Div. 2.</P>