• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제36권6호
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• pp.603-608
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• 2023

Carbon black with high purity and excellent conductivity is used as a conductive filler in the semiconductive compound for EHV (Extra High Voltage) power cables of 345 kV or higher. When carbon black and CNT (carbon nanotube) are applied together as a conductive filler of a semiconductive compound, stable electrical properties of the semiconductive compound can be maintained even though the amount of conductive filler is significantly reduced. In EHV power cables, since the semi-conductive layer is close to the conductor, stable electrical characteristics are required even under high-temperature conditions caused by heat generated from the conductor. In this study, the theoretical principle that a semiconductive compound applied with carbon black and CNT can maintain excellent electrical properties even under high-temperature conditions was studied. Basically, the conductive fillers dispersed in the matrix form an electrical network. The base polymer and the matrix of the composite, expands by heat under high temperature conditions. Because of this, the electrical network connected by the conductive fillers is weakened. In particular, since the conductive filler has high thermal conductivity, the semiconductive compound causes more thermal expansion. Therefore, the effect of CNT as a conductive filler on the thermal conductivity, thermal expansion coefficient, and volume resistivity of the semiconductive compound was studied. From this result, thermal expansion and composition of the electrical network under high temperature conditions are explained.

• Journal of the Korean Society for Nondestructive Testing
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• 제33권4호
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• pp.336-341
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• 2013

In this paper, the design concept of a low-temperature vacuum blackbody was described, and thermophysical model of the blackbody was numerically evaluated. Also the working performance of low-temperature vacuum blackbody was evaluated using infrared camera system. The blackbody system was constructed to operate under high-vacuum conditions ($2.67{\times}10^{-2}$ Pa) to reduce temperature uncertainty, which is caused by vapor condensation at low temperatures usually below 273 K. In addition, both heat sink and heat shield including cold shield were installed around radiator to prevent heat loss from the blackbody. Simplified mathematical model of blackbody radiator was analyzed using modified Stefan-Boltzmann's rule. The infrared radiant performance of the blackbody was evaluated using infrared camera. Based on the results of measurements, and simulation, temperature stability of the low-temperature vacuum blackbody demonstrated that the blackbody system can serve as a highly stable reference source for the calibration of an infrared optical system.

• Applied Chemistry for Engineering
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• 제9권6호
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• pp.884-888
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• 1998

Effects of heating time under high temperature on the thermal and mechanical properties of neutron shielding materials based on modified (KNS-102), hydrogenated(KNS-106) bisphenol-A type epoxy resin and phenol-novolac(KNS-611) type epoxy resin for radioactive material shipping casks have been investigated. At early stages, the initial decomposition temperatures of the shielding materials of KNS-102, KNS-106 and KNS-611 increased with the heating time under high temperature, but it was rarely affected by the heating time in the later stages. In addition, the thermal conductivities of KNS-102 and KNS-106 decreased with heating time, but that of KNS-611 increased with the heating time. On the contrary, the thermal expansion coefficients of neutron shielding materials decreased with increase of heating time. At the high temperature, the tensile strength and flexural strength of the shielding materials of KNS-102 and KNS-611 increased with heating time, but those of KNS-106 decreased with increase of heating time. And the heating time under high temperature on the neutron shielding materials did not show measurable loss of weight and hydrogen content.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 방전 플라즈마 유기절연재료 초전도 자성체연구회
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• pp.133-137
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• 2004

In this paper, we investigated impurities content, absorption properties, and thermal properties showing by changing the content of carbon black which is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens and absorption properties were measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer) and Karl Fisher. And high temperature, heat degradation initiation temperature, and heat weight loss were measured by TGA (Thermogravimetric Analysis). The dimension of measurement temperature was 0$[^{\circ}]$ to 800$[^{\circ}]$, and rising temperature was 10$[^{\circ}/min]$. Impurities content was highly measured according to increasing the content of carbon black from this experimental result also absorption amount was increased according to these properties. Specially, impurities content values of the A1 and A2 of existing resins were measured more than 4000[ppm]. Heat degradation initiation temperature from the TGA results was decreased according to increasing the content of carbon black. All over, heat stabilities were EEA>EBA>pEVA. That is, heat stabilities of EVA containing the weak VA(vinyl acetate) against heat was measured the lowest.

• Progress in Superconductivity and Cryogenics
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• 제24권4호
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• pp.59-64
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• 2022

The cryogenic system of RAON which is Korea's first heavy ion accelerator was numerically modeled and simulated. EcosimPro which is widely used off-the-shelf numerical software for a large scale cryogenic system was used for the simulation. The model of SRF TF cryogenic system, which is the testbed of cryomodule, was firstly established. The integrity of system of SRF TF was confirmed by comparison of simulation and experimental results. The cool-down strategy to minimize the thermal stress of the cavity was simulated and an optimal strategy was established. In addition, the influence of valve and pump control parameters on the cooling time was investigated, and optimal control parameters were also derived. The cryogenic system of SCL3 that is a low-energy acceleration section including 55 cryomodules, valve boxes, and helium supply lines was also modeled. The soundness of the thermal shield system and interlock system of SCL3 was investigated.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4246-4251
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• 2023

The optimized design of a Neutron Activation Analysis (NAA) system, including Delayed Gamma NAA (DGNAA) and Prompt Gamma NAA (PGNAA), has been proposed in this research based on Mevex Linac with 5 MeV electron energy and 50 kW power as a neutron source. Based on the MCNPX 2.6 simulation, the optimized configuration contains; tungsten as an electron-photon converter, BeO as a photoneutron target, BeD₂ and plexiglass as moderators, and graphite as a reflector and collimator, as well as lead as a gamma shield. The obtained thermal neutron flux at the beam port is equal to 2.06 × 10⁹ (# /cm².s). In addition, using the optimized neutron beam, the detection limit has been calculated for some elements such as H-1, B-10, Na-23, Al-27, and Ti-48. The HPGe Coaxial detector has been used to measure gamma rays emitted by nuclides in the sample. By the results, the proposed system can be an appropriate solution to measure the concentration and toxicity of elements in different samples such as food, soil, and plant samples.

• Transactions on Electrical and Electronic Materials
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• 제10권6호
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• pp.217-221
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• 2009

The use of the carbon nanotube (CNT) is superior to the general powder state materials in their thermal and chemical properties. Because its ratio of diameter to length (aspect ratio) is very large, it is known to be a type of ideal nano-reinforcement material. Based on this advantage, the existing carbon black of the semiconductive shield materials used in power cables can acquire excellent properties by the use of a small amount of CNTs. Therefore, we fabricated specimens using a solution mixing method. We investigated the thermal properties of the CNT, such as its storage modulus, loss modulus, and its tan delta using a dynamic mechanical analysis 2980. We found that a high thermal resistance level is demonstrated by using a small amount of CNTs. We also investigated the chemical properties of the CNT, such as the oxidation reaction by using Fourier transform infrared spectroscopy (FT-IR) made by Travel IR. In the case of the FT-IR tests, we searched for some degree of oxidation by detecting the carboxyl group (C=O). The results confirm a tendency for a high cross-linking density in a new network in which the CNTs situated between the carbon black constituent molecules show a bond using similar constructive properties.

• Journal of the Korean Society for Nondestructive Testing
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• 제36권3호
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• pp.202-210
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• 2016

A thermal barrier coating (TBC) has been widely applied to machine components working under high temperature as a thermal insulator owing to its critical financial and safety benefits to the industry. However, the nondestructive evaluation of TBC damage is not easy since sensing of the microscopic change that occurs on the TBC is required during an evaluation. We designed an eddy current probe for evaluating damage on a TBC based on the finite element method (FEM) and validated its performance through an experiment. An FEM analysis predicted the sensitivity of the probe, showing that impedance change increases as the TBC thermally degrades. In addition, the effect of the magnetic shield concentrating magnetic flux density was also observed. Finally, experimental validation showed good agreement with the simulation result.

• Journal of Ocean Engineering and Technology
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• 제6권2호
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• pp.113-124
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• 1992

The offshore industry created a need for quality wet weld repairs. Wet welding is a fast method of repair providing sound, structural quality welds. It requires less support equipment than a similar underwater dry weld repair or the alternative mechanical connections. Compared to welds made in air, underwater wet welds are plagued by increased hardness due to rapid quenching by the surrounding water. In this paper is described the experimntal study of improving the cooling rates of wet welds of TMCP steel plate by shielding around weld arc surroundings. The principal results of this experimental investigation can be summarized as follows : By shielding around weld arc surrounding, the cooling rates resulting from wet welds on TMCP steel plate could be lower than that of nonshielded wet welds and the fesibility on high quality of mecanical properties of wet weld on TMCP steel plate was carried out with shielded weld arc surrounding.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 한국방사성폐기물학회 2004년도 Proceedings of the 4th Korea-China Joint Workshop on Nuclear Waste Management
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• pp.114-129
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• 2004

The 3D simulations for the Rotary Specimen Rack (RSR), the shielding concret, and the reactor core dismantling processes in the Korea Research Reactor-1&2(KRR-1&2) were carried out in the present work. The four main dismantling items, which are the RSR, reactor core, beam tube, and the thermal column and the shield concrete, were selected among the many components in the KRR-2 by consideration of the activation, worker training, difficulty of the work and so on. On the basis of these, we built 3D CAD models, selected the proper dismantling technologies, and reviewed their dismantling processes. In this study, the 3D simulation results of the shielding concrete, and the reactor core dismantling processes are also presented and discussed.