Structural Behavior of KSTAR CS Magnet During Plasma Operation

Ahn, Hee-Jae,Park, Hyun-Ki,Kim, Jinsub,Kim, YoungOk,Kim, Kwang Pyo,Chu, Yong,Kim, Hyun-Seok,Park, Kaprai,Oh, Yeong-Kook,Lee, Sudo,Kim, Yong Hwan Institute of Electrical and Electronics Engineers 2018 IEEE transactions on applied superconductivity Vol.28 No.3

<P>The finite element model of KSTAR central solenoid (CS) magnet has been developed with new smeared orthotropic material properties of CS coils and the effective coefficient of thermal expansion of the magnet structures. The accuracy of structural analysis for assembly and cool-down processes is higher than in previous studies. Electromagnetic analysis was performed to evaluate Lorentz forces of poloidal field (PF) coils during a long pulse discharge. The analyzed structural behavior of the CS magnet was clearly consistent with the measured data and calculated Electromagnetic (EM) forces during the plasma operation. The current of PF4 coil had a significant effect on axial compression and the minimum preloading was maintained at 2.0 MN in the end of plasma. Equivalent EM force can easily predict the axial compression of CS magnet without complicated structural analysis. The study on the structural behavior of CS magnet is expected to provide the optimal combination of PF coil current limits for large plasma current and long pulse discharges.</P>

Conceptual design and implementation of Pulse Automation and Scheduling System for KSTAR

Lee, Woongryol,Lee, Taegu,Park, Jinseop,Hong, Jaesic,Hahn, Sanghee,Han, Hyunsun,Woo, Minho,Park, Kaprai Elsevier 2015 Fusion engineering and design Vol.96 No.-

<P><B>Abstract</B></P> <P>The world clock based automatic sequential operation manipulator has been developed and begin to work on the 7th campaign in KSTAR Tokamak. The Pulse Automation and Scheduling System (PASS) divided into Pulse Automation System (PAS) and Pulse Scheduling System (PSS). The PAS is on the online control system and it has communicated with many other local control systems. Before PASS, the plasma experiment was performed manually by using Central Control System (CCS). However the PASS currently manipulates the sequential operation of KSTAR with the programmed shot interval time. It provides readiness check routine, shot time handler, and local system monitoring functions. The PASS has no hardware dependency and it was configured with EPICS extensions. The Real Time Monitoring System, PCS_GATE, Automatic Reporting System, Central Control System, and Timing Synchronization System are well organized and they communicate to each other. The PASS provides perceptual operation status, easy time manipulator, and intuitive man machine interface. The plasma disruption information which is used in the KSTAR standard software framework also comes from the PASS. We describe the functions and system architecture of the Pulse Automation System in this paper. The PSS will be specified inside PASS for the purpose of intelligent system parameterization.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The world clock based automatic sequential operation manipulator. </LI> <LI> Configuration of the Pulse Automation System (PAS) and the Pulse Scheduling System (PSS) </LI> <LI> Providing of operational information in voice through an Ethernet interface. </LI> <LI> A perceptional operation status, easy time manipulator, and intuitive man machine interface for the purpose of the Tokamak operation. </LI> <LI> Generation of the plasma disruption information. </LI> </UL> </P>

전자기적 발열에서의 KSTAR In-Vessel Control Coil의 열 및 기계적 거동

강진구(Jin Gu Kang),박성현(Sunghyun Park),장민용(Minyoung Jang),이현정(Hyunjung Lee),김현욱(Hyun Wook Kim),이근수(KunSu Lee),김광표(Kwang Pyo Kim),박갑래(Kaprai Park),김범석(Beom Seok Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

To settle fusion technology, technical- and engineering challenges should be solved to control unstable fusion plasma. In-vessel control coil (IVCC) in Korea Superconducting Tokamak Advanced Research (KSTAR) has been implemented for plasma control. We characterize the mechanical behaviors of IVCC under high heat-generation environments due to electrically induced eddy currents. Numerical evaluations reveal electromagnetic-, thermal- and mechanical responses under operating conditions. Thermal stability is assessed in terms of transient temperature variations and consequent thermal stress distributions. Experimental approaches using IVCC mock-up models are employed to validate the numerical results. We suggest candidates reduce eddy current and guarantee heat-dissipating performance via tailored methods with an upgrade of the IVCC case. The preliminary results will be the fundamental data for feasible upgrade of IVCC in KSTAR.

핵융합연구장치(KSTAR장치)의 가동 중 검사 방안

김희수(Hee Soo Kim),박갑래(Park, Kaprai),조광운(Kwang-Woon Cho) 한국비파괴검사학회 2023 한국비파괴검사학회 춘계학술대회 초록집 Vol.2023 No.5

Experimental Evaluation of Inductance and Its Impact on Quench Detection of the KSTAR Coils

Yonekawa, H,Yong Chu,Young-ok Kim,Kaprai Park,Hoon-Kyun Na,Myeun Kwon IEEE 2011 IEEE transactions on applied superconductivity Vol.21 No.3

<P>Windings of Nb<SUB>3</SUB>Sn cable-in-conduit conductors of the toroidal field (TF) and the 1st-5th poloidal field (PF) coils of the Korea Superconducting Tokamak Advanced Research (KSTAR) have Incoloy-908 jackets, which exhibit weak ferromagnetism. The inductance of the PF coils was measured by monitoring the induced voltages on the coils while TF coils were steadily energized at 20 kA, and one of each pair of PF coils was charged up to 4 kA at 2 kA/s. At a large PF current, the measured self inductance was very close to the design value. In contrast, the measured self inductances of the PF1-PF5 coils increased 90-135% by decreasing their current below 2 kA; whereas those of the PF6-PF7 coils almost stayed at the same levels. On the other hand, the measured self inductances were much smaller than the other measurements obtained at no TF current. The self induced voltage was almost cancelled out by using a single Wheatstone bridge of the quench detectors; whereas, the mutually induced voltage was cancelled out by numerically subtracting outputs of two Wheatstone bridges for coils, which were symmetrically located in the assembled coils.</P>

전자기적 발열에서의 KSTAR In-Vessel Control Coil의 열 및 기계적 거동

강진구(Jin Gu Kang),박성현(Sunghyun Park),장민용(Minyoung Jang),이현정(Hyunjung Lee),김현욱(Hyun Wook Kim),이근수(KunSu Lee),김광표(Kwang Pyo Kim),박갑래(Kaprai Park),김범석(Beom Seok Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

To settle fusion technology, technical- and engineering challenges should be solved to control unstable fusion plasma. In-vessel control coil (IVCC) in Korea Superconducting Tokamak Advanced Research (KSTAR) has been implemented for plasma control. We characterize the mechanical behaviors of IVCC under high heat-generation environments due to electrically induced eddy currents. Numerical evaluations reveal electromagnetic-, thermal- and mechanical responses under operating conditions. Thermal stability is assessed in terms of transient temperature variations and consequent thermal stress distributions. Experimental approaches using IVCC mock-up models are employed to validate the numerical results. We suggest candidates reduce eddy current and guarantee heat-dissipating performance via tailored methods with an upgrade of the IVCC case. The preliminary results will be the fundamental data for feasible upgrade of IVCC in KSTAR.

Actively cooled plasma-facing components and coolant removal system in KSTAR

Bang, Eunnam,Jeong, Nam-yong,Hong, Suk-Ho,Kong, Jongdae,Park, Kaprai Elsevier 2017 Fusion engineering and design Vol.124 No.-

<P><B>Abstract</B></P> <P>This paper deals with the first commissioning of active cooling system and coolant removal system for plasma-facing components (PFCs). During 2015 KSTAR campaign, we have achieved a 55s long pulse H-mode plasma operation. However, some plasma shots were terminated, not because of instabilities or limitation of heating power, but because of safety limit applied to the PFCs temperature: upper boundary to lock the system is 400°C to protect the machine, and unlocked at 200°C. In order to overcome this limitation and to achieve longer pulse, an active cooling system is installed. With the active cooling, the temperature of lower divertor is about 302°C lower than that of upper divertor and returned quickly to initial temperature resulting in reduction of shot interval: Inertial cooling takes much longer time to unlock the safety inter-lock. One technical issue of this active cooling of PFCs is to remove coolant from the “cooling line”. The cooling line, pipe system inside the PFCs are also used to bake the PFCs. Therefore, a coolant removal system is assembled. The system is consists of adsorption dryer (external heater non purge air dryer), gas cooler, pipes and valve components. The coolant removal system was operated for 8days during PFC baking operation period. The dew point of requirement value (<−40°C) was decreased to −80°C, and then PFC baking operation was well done. And we could be achieved a 70s long pulse H-mode plasma at 2016 campaign.</P> <P><B>Highlights</B></P> <P> <UL> <LI> KSTAR have been operated the long pulse more than 50 seconds and the first commissioning of active cooling for PFC have been successfully done. </LI> <LI> After plasma shot, the temperature of PFC tiles returned quickly to initial temperature and the shot interval time is reduced. </LI> <LI> The coolant removal system is consist of adsorption dryer with 3000Nm<SUP>3</SUP>/hr of flow capacity. </LI> <LI> The PFCs baking was well operated. The PFCs baking and cooling operation was well done at a time to maintain of lower vacuum pressure, to remove the water of vacuum vessel and for cooling of PFCs. </LI> <LI> The performance and operation period of coolant removal system can be confirmed. </LI> </UL> </P>

Recovery process of wall condition in KSTAR vacuum vessel after temporal machine-vent for repair

Kim, Kwang Pyo,Hong, Suk-Ho,Lee, Hyunmyung,Song, Jae-in,Jung, Nam-Yong,Lee, Kunsu,Chu, Yong,Kim, Hakkun,Park, Kaprai,Oh, Yeong-Kook Elsevier 2015 Fusion engineering and design Vol.98 No.-

<P><B>Abstract</B></P> <P>Efforts have been made to obtain vacuum condition that is essential for the plasma experiments. Under certain situations, for example, the vacuum vessel should be vented to repair in-vessel components such as diagnostic shutter, exchange of window for diagnostic equipment, and PFC damaged by high energy plasma. For the quick restart of the campaign, a recovery process was established to make the vacuum condition acceptable for the plasma experiment. In this paper, we present the recovery process of wall condition in KSTAR after temporal machine-vent for repair. It is found that an acceptable vacuum condition has been achieved only by plasma based wall conditioning techniques such as baking, GDC, and boronization. This study was that the proper recovering method of the vacuum condition should be developed according to the severity of the accident.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Efforts have been made to obtain vacuum condition that is essential for the plasma experiments. </LI> <LI> For example, the vacuum vessel should be vented to repair in-vessel components such as diagnostic shutter, and PFC damaged by high energy plasma. </LI> <LI> Here, we present the recovery process of wall condition in KSTAR after temporal machine-vent for repair. </LI> <LI> It is found that an acceptable vacuum condition has been achieved only by plasma based wall conditioning techniques such as baking, GDC, and boronization. </LI> <LI> This study was that the proper recovering method of the vacuum condition should be developed according to the severity of the accident. </LI> </UL> </P>