Yaung-Soo Kim

CURRENT STATUS OF NUCLEAR FUSION ENERGY RESEARCH IN KOREA

The history of nuclear fusion research in Korea is rather short compared to that of advanced countries. However, since the mid-1990s, at which time the construction of KSTAR was about to commence, fusion research in Korea has been actively carried out in a wide range of areas, from basic plasma physics to fusion reactor design. The flourishing of fusion research partly owes to the fact that industrial technologies in Korea including those related to the nuclear field have been fully matured, with their quality being highly ranked in the world. Successive pivotal programs such as KSTAR and ITER have provided diverse opportunities to address new scientific and technological problems in fusion as well as to draw young researchers into related fields. The frame of the Korean nuclear fusion program is now changing from a small laboratory scale to a large national agenda. Coordinated strategies from different views and a holistic approach are necessary in order to achieve optimal efficiency and effectiveness. Upon this background, the present paper reflects upon the road taken to arrive at this point and looks ahead at the coming future in nuclear fusion research activities in Korea.

CONSTRUCTION, ASSEMBLY AND COMMISSIONING OF KSTAR MAIN STRUCTURES

The KSTAR device succeeded in first plasma generation on June of 2008 through comprehensive system test and commissioning. Among various kinds of the key factors that decisively affected the project, success in the construction and assembly of the major tokamak structure was most important one. Every engineering aspects of each structure were finally confirmed in the integrated commissioning period, and there were no severe troubles and failures prevented the KSTAR device from operating during the commissioning and the first plasma experiments. As a result, all of the experiences and technologies achieved through the KSTAR construction process are expected to be important fundamentals for future construction projects of superconducting fusion devices. This paper summarizes key engineering features of the major structures and of the machine assembly.

Stabilization of the KSTAR Power System for the First Plasma Operation

After more than ten years of construction, the Korea Superconducting Tokamak Advanced Research (KSTAR) device finally completed its assembly in June 2007. We conducted the first plasma operation from April 2008 to July 2008 and succeeded in the plasma generation in July 2008. The electric power system for the first plasma operation is made up of various electric devices, including 154-kV circuit-breaker systems, a 154/22.9-kV 50-MVA transformer, 22.9-kV circuit-breaker systems, and reactive power compensator (RPC) and harmonic filter (HF) systems. When the poloidal-field magnet power supplies were operated, the reactive power and harmonic currents (12n ± 1) were generated instantaneously in the KSTAR electric power system for the first plasma generation due to the characteristics of the KSTAR superconducting coils. The measured voltage drop and harmonics seriously affected the other experimental equipment as well. Therefore, it is important to compensate the reactive power and remove the harmonics with the RPC and HF system for the superconducting tokamak device. In this paper, we discuss the stability of the electric power system and the operational results of the RPC and HF systems during the KSTAR first plasma operation. Furthermore, the upgrade plan of the electric power system based on the KSTAR operation plan will be discussed.

Stabilization of the KSTAR power system for the first plasma operation

The KSTAR(Korea Superconducting Tokamak Advanced Research) facility is composed of thirty superconducting magnets for plasma experiment. The electric power system for the first plasma operation is made up of various electric devices including 170 kV GIS, 154 kV 50 MVA transformer, 22.9 kV circuit breaker systems and RPC & HF systems. When PF MPS was operated, reactive power and harmonic currents of 1±12ns occurred instantaneously in the KSTAR electric power system due to the characteristics of the KSTAR superconducting coil for the first plasma generation. However, the measured voltage drop and harmonics seriously affect other experiment equipments as well. Therefore, the RPC & HF system for the superconducting tokamak device is important to compensate the reactive power and remove harmonics. In this paper, we discuss the stability of the electric power system and the operation results of the RPC & HF systems during the KSTAR first plasma operation. Also, the upgrade plan of the electric power system based on the KSTAR operation plan will be discussed.

Quench Protection System for the KSTAR Toroidal Field Superconducting Coil

The design of the integrated quench protection (QP) system for the high current superconducting magnet (SCM) has been fabricated and tested for the toroidal field (TF) coil system of the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The QP system is capable of protecting the TF SCM, which consists of 16 identical coils serially connected with a stored energy of 495 MJ at the design operation level at 35.2 kA per turn. Given that the power supply for the TF coils can only ramp up and maintain the coil current, the design of the QP system includes two features. The first is a basic fast discharge function to protect the TF SCM by a dump resistor circuit with a 7 s time constant in case of coil quench event. The second is a slow discharge function with a time constant of 360 s for a daily TF discharge or for a stop demand from the tokamak control system. The QP system has been successfully tested up to 40 kA with a short circuit and up to 34 kA with TF SCM in the second campaign of KSTAR. This paper describes the characteristics of the TF QP systems and test results of the plasma experiment of KSTAR in 2009.

A reactive power compensation and harmonics removal of superconducting nuclear fusion device through tsc base massive RPC & HF systems

The KSTAR(Korea Superconducting Tokamak Advanced Research) device needs a large pulse power to supply to a superconducting magnet power supply(MPS) and a heating device to generate plasma and restrict plasma.