• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.278-280
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• 2003

We manufactured neon liquefaction system for cooling system of HTS motor. The neon liquefaction system consists of a GM refrigerator, a liquefaction vessel and a vacuum chamber. It is found that the neon starts to be liquefied in the liquefaction vessel after 35 minutes of cool-down from gas state of 294k. Capacity of neon liquefaction system and the liquefaction rate were about 36W, 0.1g/s.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3012-3017
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• 2021

The spatial distribution and the energy spectrum of the neutron yield were investigated with the neutron activation analysis and MCNP simulation was carried out to verify the analysis results and to extend the results to a 3D mapping of the neutron yield distribution in the KSTAR. High purity Ni specimen was selected in the neutron activation analysis. Total neutron yields turned out to be 3.76 × 10¹² n/s - 7.56 × 10¹² n/s at the outer vessel of the KSTAR, two orders of magnitude lower than those at the inner vessel of the KSTAR, which demonstrates the attenuation of neutron yield while passing through the different structural materials of the reactor. Based on the fully expanded 3D simulation results, 2D cross-sectional distributions of the neutron yield on XY and ZX planes of KSTAR were examined. The results reveal that the neutron yield has its maximum concentration near the center of blanket and decreases with increasing proximity to the vacuum vessel wall.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.10
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• pp.1558-1565
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• 2004

It is important to determine supporting locations for structural stability when a structure is loaded with non-uniform load or supporting locations as well as the number of the supporting structures are restricted by the problem of space. Moreover, the supporting location optimization of complex structure in real world is frequently faced with discontinuous design space. Therefore, the traditional optimization methods based on derivative are not suitable Whereas, Genetic Algorithm (CA) based on stochastic search technique is a very robust and general method. The KSTAR in-vessel control coil installed in vacuum vessel is loaded with non- uniform electro-magnetic load and supporting locations are restricted by the problem of space. This paper shows the supporting location optimization for structural stability of the in-vessel control coil. Optimization has been performed by means of a developed program. It consists of a Finite Element Analysis interfaced with a Genetic Algorithm. In addition, this paper presents an algorithm to find an optimum solution in discontinuous space using continuous design variables.

• Nuclear Engineering and Technology
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• v.56 no.8
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• pp.2990-2998
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• 2024

In ITER, the evaluation of the activated water radiation source and its impact on the radiological levels is necessary to demonstrate compliance with the safety requirements. The use of simplified or conservative approaches often results in the application of expensive constraints on the installation that impact its economics, operations, and construction schedule. In this work, we propose a novel methodology to calculate the activated water source term with a higher degree of realism. The methodology is based on the coupling of a system-level code with a Computational Fluid Dynamics (CFD) code in an explicit, one-way approach. We apply this methodology to the evaluation of the16N radioisotope within the ITER Vacuum Vessel Primary Heat Transfer System (VV-PHTS) cooling circuit in a steady-state and transient scenarios. We chose this system since previous analyses of the VV-PHTS were done with simple, ad-hoc calculations that yielded results that differed by up to a factor of five, underscoring a higher level of uncertainty. As a result, we generate a computational model of the source term that can be used to evaluate the radiological condition surrounding the cooling systems during the operations.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.425.2-425.2
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• 2016

토카막(TOKAMAK) 장치의 진공용기 및 용기내벽은 플라즈마(Plasma)에 의한 고열과 높은 에너지의 이온 입자들에 항상 노출되어 있는 환경이다. 토카막의 일종인 KSTAR장치의 진공용기는 스테인레스강(STS316)계열의 재질로 이루어져 있고, 플라즈마와 면하는 용기 벽면은 플라즈마에 대해 견딜 수 있도록 그라파이트 타일(graphite tile)로 구성되어 있다. 고에너지의 이온 입자들과 열플럭스(Heatflux)는 용기벽면과 용기를 침식시키고, 또한 이렇게 생겨난 분진(dust)들은 진공용기 내 여기저기를 떠다니게 되고, 플라즈마에 대해서 불순물로서 작용하게 된다. 본 연구에서는 감마분석법으로 플라즈마에 의해 진공용기 내에 집적된 분진들의 구성 성분을 분석하여 주요 출처를 규명할 수 있는 방법을 제시하고, KSTAR 플라즈마의 불순물 제어에 유용하게 활용 할 수 있는 데이터를 제공하여 향후 KSTAR의 고성능 플라즈마 기술개발에 일조할 수 있도록 하고자 한다.

• Progress in Superconductivity and Cryogenics
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• v.22 no.3
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• pp.25-30
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• 2020

The diminishing of heat leak into cryogenic vessels can prolong the storage time of cryogenic liquid. With the storage of cryogenic liquid reducing, the heat leak decreases, while the actual storage time increases. Regarding to the theoretical analysis, the obtained results seems to be constructive for the cryogenic insulation system applications. This study presents a predictive assessment of heat leak occurring in non-vacuum tanks with a single layer of insulation. A Radial steady-state heat transfer, based on heat conduction equation, is taken into consideration. Graphical results show the thermal performance of the insulation used, they also allow us to choose the appropriate insulation thickness according to the shape and diameter of the storage tank.

• Progress in Superconductivity and Cryogenics
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• v.14 no.2
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• pp.32-35
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• 2012

The objective of the present work is to develop a precise instrument for measuring the thermal property of insulating material over a temperature range from 30 K to near room temperature by utilizing a cryocooler. The instrument consists of two thermal links, a test sample, heat sink, heat source and vacuum vessel. The cold head of the cryocooler as a heat sink is thermally anchored to the thermal link and used to bring the apparatus to a desired temperature in a vacuum chamber. An electric heater as a heat source is placed in the middle of test sample for generating uniform heat flux. The entire apparatus is covered by thermal shields and wrapped in multi-layer insulation to minimize thermal radiation in a vacuum chamber. For a supplied heat flux the temperature distribution in the insulating material is measured in steady and transient state. The thermal conductivity of insulating material is measured from temperature difference for a given heat flux. In addition, the specific heat of insulating material is obtained by solving one-dimensional heat diffusion equation.

• Journal of the Korean Vacuum Society
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• v.11 no.2
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• pp.81-86
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• 2002

With a specific model for the Helicoflex type metal gasket expected to be used in large ports of the KSTAR vacuum vessel, a sealing curve was obtained by measuring the flange tightening properties such as the correlations of the tightening torque(or linear load), displacement to the leak rate. From the experiment results it was found that the leak rate of the Helicoflex seal in the room temperature was bellow $2\times10^{-1}\textrm{mbar\cdot L/s}$ with a tightening torque of 2500kgf . cm using Ml8 bolts.

• Journal of Energy Engineering
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• v.17 no.1
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• pp.15-22
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• 2008

This study was carried out to investigate physical and chemical characteristics of the distillates and residue of Athabasca oilsand bitumen obtained from Canada, using a vacuum distillation unit. The distillates and residue produced from the vacuum distillation were characterized through atomic analysis, SARA analysis, and measurement of boiling point distribution, molecular weight, and API gravity. The vacuum distillation equipment consisted of a 6-litter volume vessel, a glass-packed column, a condenser, a reflux device, a flask fer collecting distillates, and a temperature controller. The cutting of distillates was performed with four steps under the condition of full vacuum and maximum temperature of $320^{\circ}C$. The results showed that the sulfur amount and average molecular weight of the distillates were significantly reduced compared to those of oilsand bitumen. As the cutting temperature increased, the hydrogen amount decreased but the sulfur amount and average molecular weight increased in the distillates.

• Journal of Hydrogen and New Energy
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• v.10 no.3
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• pp.151-157
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• 1999

The development of hydrogen vehicles has been actively progressed in the developed countries such as U. S., Japan and Germany. The most important technology of using hydrogen fuel is to develope a compatible storage tank with respect to the fossil fuel tank. Among many storage methods, the liquid hydrogen is the most desirable state because of the lowest volume and weight. The metal hydride tank is too heavy and the compressed hydrogen tank is too bulky. Because of these reasons, it is the principal purpose to analyze the theoretical heat transfer for designing and manufacturing an actual $LH_2$ tank. The insulation methods of the room between inner and outer vessel are non-vacuum, vacuum, vacuum with MLI(Multi-Layer Insulation). According to the results of the numerically calculated heat leak through the walls of the $LH_2$ tank, the vacuum insulated tank has 20 times and the MLI tank has 5616 times less heat leak than the non-vacuum tank.