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Development of tungsten brazing technology for the upgraded Korea superconducting tokamak advanced research divertor was launched in early 2013. ITER grade tungsten block was brazed on the CuCrZr alloy in vacuum at 980 °C for 30 min using silver free brazing alloy. An OFHC-copper was used as an interlayer between tungsten and the CuCuZr. The brazing alloy is a 0.05 mm thickness of plate of which component is a Ni–Cu–Mn. It is found that the optimal loading on mock-up is about 20 kPa. Ultrasonic test and shear strength test were carried out to check the strength between tungsten and substrate material. And the joint conditions were analyzed by scanning electron microscopy. Tungsten-brazed mock-ups with a cooling tube were tested at the electron beam facility, Korea heat load test facility-electron beam in Korea Atomic Energy Research Institute. The high heat flux test was performed for tungsten-brazed mock-ups under heat flux of about 5 MW/ $\text{m}^{2}$ with more than 2000 cycles. All the tungsten-brazed mock-ups met the requirements and there was no delamination or failure at the bonding joints.

Tungsten (W) monoblock that consists of W according to ITER specifications, oxygen-free high conductive copper (Cu-OFHC), and CuCrZr has been designed in preparation for KSTAR upgrade for steady-state long-pulse operation with 27.5-MW heating power. Finite-element analysis has been performed by ANSYS Workbench. The hydraulic thermomechanical analysis is performed to investigate the optimal design parameters and the expected fatigue lifetime under the operating conditions with 5.4-MW/ $\text{m}^{2}$ incident heat flux at the divertor. For a single W monoblock, the optimization gives a W thickness of 5 mm, a side thickness of 2.5 mm, a thickness in the back part of 6 mm, and a Cu-OFHC interlayer thickness of 0.5 mm. For a mock-up consisting of five optimized W monoblocks, the thermal fatigue analysis is performed. As a result, the maximum value of equivalent total strain in the CuCrZr tube is found to be 0.266%, which corresponds to for a fatigue lifetime of 23 000 cycles.

In and outboard plasma facing components (PFCs) of Korea Superconducting Tokamak Advanced Research (KSTAR) have been fully installed in 2010 for D-shaped diverted plasmas. Before the start of plasma operation, the PFCs were baked up to 200 by hot nitrogen gas circulation system to remove impurities including water. The surface temperature of the PFC tiles was monitored by 200 thermocouple sensors during the plasma operation [plasma shot or glow discharge cleaning (GDC)], and the temporal and spatial (poloidal) temperature profiles are obtained. Depending on the heat flux on each tile, the surface temperature shows time-dependent behavior. After 1-h morning He GDC, the temperature of the PFCs at the inboard side has reached to 40 . After an H-mode shot, the temperature of divertor tiles around the striking points was substantially increased. The time-averaged total heat flux after a few of L- and H-modes in 2010 was estimated to be approximately 0.010 .

A continuous production of carbon black and hydrogen has been investigated by thermal decomposition of methane using a prototype processing system of direct current (dc)-radio frequency (RF) hybrid thermal plasma, which has great advantage over other thermal sources like combustion or dc plasma torches in synthesizing new nanostructured materials by providing high-temperature environment and longer residence time for reactant gases due to its larger hot core region, and lower flow velocity. Appropriate operation conditions and reactor geometries for the effective synthesis process are predicted first from the relevant theoretical bases, such as thermodynamic equilibrium calculations, two-dimensional thermal flow analysis, and chemical kinetic simulation. Based on these derived operation and design parameters, a reaction chamber and a dc-RF hybrid torch are fabricated for the processing system, which is followed by methane decomposition experiments with it. The methane injected into the processing system is converted mostly into hydrogen with a small volume fraction of acetylene, and fine carbon particles of 20-50 nm are identified from their transmission electron microscope images. Material analyses of Brunauer-Emmett-Teller , dibutyl phthalate adsorption, and X-ray diffraction indicate that the synthesized carbon black has excellent properties, such as large surface area, high electrical conductivity, and highly graphitized structures with good crystallization.

Summary form only given, as follows. In plasma spraying, higher temperature and velocity of thermal plasma jets are preferable for producing high qualities of protective coatings for their industrial uses, because the sprayed coating powders are melted and accelerated in the plasma flame ejected from a non-transferred DC arc torch through an ambient air toward a substrate. In the typical plasma spray process operated under an atmospheric-pressure condition, the entrainment, of ambient air into the thermal plasma jet is inevitable. An air inflow to the flame alters chemical compositions of the plasma species, cools the thermal plasma flame, and decreases the jet velocity. Furthermore, the dissociation of entrained air enhances the specific heat of plasma, and then the plasma temperatures decrease even when operation power level of the plasma torch is not changed. Consequently, the gradients of temperature and velocity in the plasma jet increase with the degree of air entrainment. Therefore, the ambient air entrainment should be controlled to the lower degree for getting the better quality of coating products with higher purity, density and bond strength. In this experimental work, the geometrical effects of anode nozzle of the non-transferred plasma torch on the air entrainment are examined by measurements using a quadruple mass spectrometer. Two different types of anode nozzle, i.e., tubular and stepped nozzles are employed for the torch. For each nozzle, air contents in the thermal plasma are measured to find the effects of nozzle geometry on the ambient air mixing with the plasma species. The radial and axial distributions of plasma temperature and velocity are also measured. By analyzing the measured results of the thermal plasma characteristics and the geometrical effects of nozzle shape on the air entrainment, the suitable design requirements of the nozzle are determined for optimal processes of plasma spraying.