• Proceedings of the KSME Conference
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• 2000.11b
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• pp.247-254
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• 2000

The base pressure of vacuum vessel of the KSTAR (Korea Superconducting Tokamak Advanced Research) Tokamak is to be a ultra high vacuum, $10^{-6}{\sim}10^{-7}Pa$, to produce clean plasma with low impurity containments. For this purpose, the KSTAR vacuum vessel and plasma facing components need to be baked up to at least $250^{\circ}C,\;350^{\circ}C$ respectively, within 24 hours by hot nitrogen gas from a separate baking/cooling line system to remove impurities from the plasma-material interaction surfaces before plasma operation. Here by applying the implicit numerical method to the heat balance equations of the system, overall temperature distributions of the KSTAR vacuum vessel and plasma facing components are obtained during the whole baking process. The model for 2-dimensional baking analysis are segmented into 9 imaginary sectors corresponding to each plasma facing component and has up-down symmetry. Under the resulting combined loads including dead weight, baking gas pressure, vacuum pressure and thermal loads, thermal stresses in the vacuum vessel during bakeout are calculated by using the ANSYS code. It is found that the vacuum vessel and its supports are structurally rigid based on the thermal stress analyses.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.3
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• pp.158-168
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• 2015

To create an ultra-high vacuum state at the KSTAR, the temperature of plasma facing component and vacuum vessel should be maintained at $300^{\circ}C$ and $110^{\circ}C$ respectively at a baking phase. The purpose of this research is obtaining the target baking temperatures. Experiments were performed to investigate the temperature characteristics of PFC and VV at the baking phase. Thermal network analysis was used to find heat transfer rates among PFC, VV and other components, and this analysis was verified by using the experimental data. The required heating energy of the PFC and the heating and cooling energy of the VV for the target baking temperatures were found to be 346 kW, 28 kW, and 136 kW, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.468-468
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• 2014

우리나라는 미국, EU, 러시아, 중국, 인도 등 다국간 협력 사업인 국제핵융합실험로(ITER) 사업에 참여하고 있으며, 블랑켓 일차벽 및 시험용 블랑켓 모듈(Test Blanket Module, TBM) 제작기술 개발에 필요한 고열부하 검증시험을 국내에서 자체적으로 실시하기 위한 고열부하시험 시설을 구축하였다. 한국원자력연구원에 설치된 고열부하시험 시설의 주요 사양은 다음과 같다. 열원으로는 전자빔을 사용하며, 빔출력은 최대 300 kW이고, 최대 출력밀도는 $10GW/m^2$이다. 전자빔의 최대 가속전압은 60 kV이고, 최대 조사 면적은 설계상 $70cm{\times}50cm$이다. 고열부하 장비는 핵융합환경과 유사한 고열부하를 시험대상물에 인가하여 접합 및 냉각 성능을 평가하는 장비이며, ITER 블랑켓 및 TBM 일차벽의 경우 약 $0.5MW/m^2$, 가속실험 혹은 사고 시 순간 시나리오 해석을 위해서 $5MW/m^2$까지 고려되기도 한다. ITER 블랑켓 일차벽 제작기술 개발 및 검증(2004~2011)에서는 외국장비(러시아 TSEFEY, 일본 JEBIS, 독일 JUDITH)를 활용하였으나, 고비용 문제와 장비 이용 시간의 제한에 따라 사용이 어려워, 국내에서는 KoHLT-1, 2 장비를 자체 구축하여 활용하여 왔다. 현재는 높은 열부하 인가조건, 약 $5MW/m^2$을 달성하기 위해서 전자빔을 이용한 고열부하시험 장치를 마련하였으며, ITER 블랑켓 일차벽 Semi-Prototype 검증시험, TBM, KSTAR 디버터 실험 등 핵융합로 일차벽 개발에 활용하고 있다. 전자빔, 전원 및 진공 chamber 등 전체 고열부하 시험장치를 구축하여 ITER 장치를 포함해서 토카막 디버터 등 핵융합 플라즈마 대면부품 (Plasma Facing Components, PFC) 재료 개발과 국방, 항공우주 분야의 열유속 게이지 측정법 향상 연구, 로켓 추진 엔진 연소실의 열유속 모니터링 연구, 항공기 프로펠러 연구 등에 활용할 수 있을 것으로 기대된다.

• Interaction and multiscale mechanics
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• v.4 no.3
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• pp.207-217
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• 2011

International efforts have focused recently on the development of tungsten surfaces that can intercept energetic ionized and neutral atoms, and heat fluxes in the divertor region of magnetic fusion confinement devices. The combination of transient heating and local swelling due to implanted helium and hydrogen atoms has been experimentally shown to lead to severe surface and sub-surface damage. We present here a computational model to determine the relationship between the thermo-mechanical loading conditions, and the onset of damage and failure of tungsten surfaces. The model is based on thermo-elasticity, coupled with a grain boundary damage mode that includes contact cohesive elements for grain boundary sliding and fracture. This mechanics model is also coupled with a transient heat conduction model for temperature distributions following rapid thermal pulses. Results of the computational model are compared to experiments on tungsten bombarded with energetic helium and deuterium particle fluxes.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3717-3723
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• 2022

For the first time, two-dimensional temporal behavior of the edge localized mode (ELM) filament is measured in the edge tokamak plasma with a multi-channel electrical probe array (MCEP). MCEP, which has 16 floating probes (4 × 4), is mounted at the far scrape-off layer (SOL) region in the KSTAR. An electron temperature and an ion flux are measured by sideband method (SBM), which can achieve two-dimensional measurements with high time resolution. Furthermore, temporal evolutions of the electron temperature and the ion flux are obtained during the ELM occurrence. In the H-mode period, short spikes from ELM bursts are observed in measured plasma parameters, and the trend is similar to that of typical Hα signal. Interestingly, when blob-like ELM filaments crash the probe, the heat flux is significantly higher in a local region of the probe array. The results show that our probe array using the SBM can measure the ELM behavior and the plasma parameters without the effect of the stray current caused by the huge device. This study can provide valuable data needed to understand the interaction between the SOL plasma and the plasma facing components (PFCs).