Young-Dug Bae

Fabrication of prototype ICRF antenna for KSTAR and first RF test

Abstract A prototype ICRF antenna has been fabricated and is being tested for the development of long pulse (300 s), high power ICRF system of KSTAR. The antenna has many cooling channels inside the current strap, Faraday shield, cavity wall and vacuum transmission line to remove the dissipated RF loss power and incoming plasma heat loads. The antenna is installed in the RF test chamber evacuated by 2000 l/s turbomolecular pump and consistency with the design requirement for long pulse, high power operation is being investigated through the RF test. With the half of a current strap connected to the matching circuit via a vacuum feedthrough and a directional coupler, and the other seven ports shorted at the input ports, intermediate RF power test has been performed at f=32 MHz. During the RF pulse, the maximum peak voltage, forward/reflected powers, temperature on the antenna and gas pressure are measured. Even the initial test results promise that the long pulse, high power operation of the ICRF system will be obtainable for the advanced tokamak operation of KSTAR tokamak.

Small Mock-Up Fabrication and High Heat Flux Test for Preparing the 2nd Qualification of the ITER Blanket First Wall

Abstract For the second qualification of the blanket First Wall (FW) procurement of the International Thermonuclear Experimental Reactor (ITER), a semi-prototype of the FW has been designed with increased local surface heat flux up to 5 MW/m2. In order to investigate the fabrication procedure and methods, two types of mock-up were fabricated; one was with twelve Be tiles for high heat flux test to check the joining integrity between Be tiles and the bending Cu block and the other was for testing the thermal-hydraulic prediction by commercial code, ANSYS-CFX when it has a complex geometry such as hypervapotron, which was used for designing the semi-prototype. The former was successfully fabricated and the test conditions were obtained through the preliminary analysis with ANSYS-CFX. The later was successfully fabricated and the test with KoHLT-2 (Korea Heat Load Test facility) was performed; mass flow rate of inlet coolant was the same as the ITER condition and heat flux was loaded up to 0.65 MW/m2. The results show that the temperature of the mock-up can be predicted using the ANSYS-CFX even with the complex geometry.

Development of a High Heat Load Test Facility KoHLT-1 for a Testing of Nuclear Fusion Reactor Components

A high heat flux test facility using a graphite heating panel was constructed and is presently in operation at Korea Atomic Energy Research Institute, which is called KoHLT-1. Its major purpose is to carry out a thermal cycle test to verify the integrity of a HIP (hot isostatic pressing) bonded Be mockups which were fabricated for developing HIP joining technology to bond different metals, i.e., Be-to-CuCrZr and CuCrZr-to-SS316L, for the ITER (International Thermonuclear Experimental Reactor) first wall. The KoHLT-1 consists of a graphite heating panel, a box-type test chamber with water-cooling jackets, an electrical DC power supply, a water-cooling system, an evacuation system, an He gas system, and some diagnostics, which are equipped in an authorized laboratory with a special ventilation system for the Be treatment. The graphite heater is placed between two mockups, and the gap distance between the heater and the mockup is adjusted to . We designed and fabricated several graphite heating panels to have various heating areas depending on the tested mockups, and to have the electrical resistances of ohms during high temperature operation. The heater is connected to an electrical DC power supply of 100 V/400 A. The heat flux is easily controlled by the pre-programmed control system which consists of a personal computer and a multi function module. The heat fluxes on the two mockups are deduced from the flow rate and the coolant inlet/out temperatures by a calorimetric method. We have carried out the thermal cycle tests of various Be mockups, and the reliability of the KoHLT-1 for long time operation at a high heat flux was verified, and its broad applicability is promising.

Performance Test of the Electromagnetic Pump in an Experimental Liquid Breeder Loop for Developing a KO Test Blanket Module

Abstract Korea(KO) has developed liquid a breeder blanket and participated in the Test Blanket Module (TBM) program within the International Thermonuclear Experimental Reactor (ITER) with a Helium Cooled Molten Lithium (HCML) concept. To develop the liquid breeder technologies with not only liquid lithium but also lead-lithium (PbLi), an Experimental Loop for a Liquid breeder (ELLI) was constructed at Korea Atomic Energy Research Institute (KAERI). The main purposes of the loop are developing components such as an electromagnetic (EM) pump, testing the effects of magneto-hydro-dynamics (MHD), and investigating the compatibility between liquid breeder and other materials. In the present study, the measurement results of a magnetic field in the fabricated magnet, and a performance test of the EM pump, were introduced in order to validate their designs; the magnet used for the MHD test with a liquid PbLi was designed to produce about 2 T, and the measurement results show that the maximum field was about 2.2 T with a ferritic martensitic (FM) steel channel. The EM pump was designed to circulate the liquid PbLi at up to 60 Ipm, and was tested for up to 11 lpm. The test showed good agreement with the input power to the EM pump.

High Heat Flux Test of the KO Standard Mockups for ITER First Wall Semi-Prototype

Abstract The Korean standard mockups with beryllium tile were fabricated to perform the high heat flux test for the qualification test of ITER blanket first wall. These mockups include the 80 mm × 80 mm beryllium armor tiles joined to the CuCrZr heat sink with stainless steel cooling tubes by HIP (Hot Isostatic Pressing) technology. The high heat flux tests were performed in the Korea heat load test facility (KoHLT-1) with the averaged surface heat flux of 1.25 MW/m2 by using a graphite heater. Preliminary thermal and mechanical analyses were carried out to simulate the test conditions and to determine the number of cycles for the fatigue lifetime of the mockups. In our KoHLT-1 facility, the normal heat cycle was based on an expected heat flux of 1.25 MW/m2, and each mockup had to endure the 1,000 normal heat cycles in this heat flux in accordance with the mechanical simulation. In the cyclic heat flux tests, the maximum surface temperature of the beryllium tiles was controlled below 400 °C. As a result of these high heat flux tests with the acceptance criteria of the ITER blanket first wall, the manufacturing technologies of the Korean standard mockups will be utilized to develop the tokamak blanket for the international qualification procedure.

DISTRIBUTED CONTROL SYSTEM FOR KSTAR ICRF HEATING

An ICRF discharge cleaning and a fast wave electron heating experiment were performed. For automated operation and providing the diagnostics of the ICRF system, the ICRF local network was designed and implemented. This internal network provides monitoring, RF protection, remote control, and RF diagnostics. All the functions of the control system were realized by customized DSP units. The DSP units were tied by a local network in parallel. Owing to the distributed feature of the control system, the ICRF local control system is quite flexible to maintain. Developing the subsystem is a more effective approach compared to developing a large controller that governs the entire system. During the first experimental campaign of the KSTAR tokamak, the control system operated as expected without any major problems that would affect the tokamak operation. The transmitter was protected from harmful over-voltage events through reliable operation of the system.