• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1206-1212
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• 2022

Cold-crucible induction melting (CCIM) technology has been intensively studied as an advanced vitrification process for the immobilization of highly radioactive waste. This technology uses high-frequency induction to melt a glass matrix and waste, while the outer surface of the crucible is water-cooled, resulting in the formation of a frozen glass layer (skull). In this study, for the fabrication of borosilicate glass waste form, CCIM operation test with 60 kg of glass per batch was conducted using surrogate wastes composed of Cs, Sr, and Nd as a representative of highly radioactive nuclides generated during spent nuclear fuel management. A 60 kg-scale glass waste form was successfully fabricated through melting and draining processes using a CCIM system, and its physicochemical properties were analyzed. In particular, to enhance the controllability and reliability of the draining process, an air-cooling drain control method that can control draining through air-cooling near drain holes was developed, and its validity for draining control was verified. The method can offer controllability on various draining processes, such as molten salt or molten metal draining processes, and can be applied to a process requiring high throughput draining.

• 대한금속재료학회지
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• 제46권2호
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• pp.65-68
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• 2008

Generally CCM (cold crucible melting) is not suitable for melting glass. However, in this study we described the quantitative relationship between the basic property of glass and power balance, the power absorption in the melt, the losses in the coil and the cold crucible, for melting glass in CCM. The dependence of power balance on the applied frequency and the electric conductivity has been found. Above 300 kHz, the glass (B) contained alkali ion which has the low resistance $3.0{\Omega}{\cdot}cm$ at $900^{\circ}C$ and $1.36{\Omega}{\cdot}cm$ at $1,100^{\circ}C$ was melted easily and 60% of the overall power was absorbed in the melt and 30% and 10% of the overall power was lost in the cold crucible and coil respectively. Under the same condition, the glass (A) contained non-alkali ion was not melted easily and 50% of the overall power was absorbed in the melt and 40% and 10% of the overall power was lost in the cold crucible and coil respectively. In conclusion, the small absorbed power of the overall power in melt prevented a successful melting as for glass A, and the successful melting depends on the relative size of the absorbed power in melt irrespective of the melting volume. Hence, as typical for direct induction heating method(CCM), the successful melting strongly depended on the chosen working frequency based on electric conductivity of glass, power balance and the control of the critical power which was absorbed in melt.

• 한국결정성장학회지
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• 제29권1호
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• pp.24-31
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• 2019

사파이어 단결정을 성장시키는 기존 합성방법들의 원료충진율을 높이기 위한 방법으로 스컬용융법을 사용하여 $Al_2O_3$ 파우더를 용융시켰다. 냉각도가니 크기는 내경 24 cm, 내부 높이 30 cm로서 2.75 MHz 발진주파수에서 15 kg의 $Al_2O_3$ 파우더를 1시간 내에 모두 용융시켰으며, 3시간 동안 융액상태로 유지 후 자연냉각 시켰다. 냉각된 잉곳의 부분별 면밀도 및 성분은 SEM-EDS를 통해 분석하였다. 잉곳의 면밀도 및 $Al_2O_3$ 함량은 고주파유도가열 시 냉각도가니 내부에 형성되는 온도 분포와 관련이 있으며, 온도가 높게 형성되었던 부분이 면밀도 및 순도가 높게 나타나는 경향을 보였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.94-97
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• 2005

For the fabrication of poly-crystalline silicon ingot, CCCC (Cold Crucible Continuous Casting) method under a high frequency alternating magnetic field, was utilized in order to prevent crucible consumption and ingot contamination and to increase production rate. In order to effectively and continuously melt and cast silicon, which has a high radiation heat loss due to the high melting temperature and a low induction heating efficiency due to a low electric conductivity, Joule and pinch effects were optimized. Throughout the present investigation, poly-crystalline Si ingot was successfully produced at the casting speed of above 1.5 mm/min under a non-contact condition.

• 한국결정성장학회지
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• 제15권5호
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• pp.175-181
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• 2005

스컬용융법에 의해 루틸 단결정들을 성장시켰으며, 서로 다른 융액의 유지시간에 따른 ingot의 특성을 비교하였다. 스컬용융법은 교류전자기장(RF)에 의해 전기가 흐르는 융액의 직접유도가열에 근거하며, 가열은 RF 에너지의 흡수로 실행된다. $TiO_2$는 상온에서는 부도체이지만 온도가 올라갈수록 전기 전도성이 증가한다. 따라서, 초기 RF 유도가열을 위해 티타늄 금속 링(외경 : 6cm, 내경 : 4cm, 두께 : 0.2cm)을 $TiO_2$ 분말(아나타제상, CERAC, 3N)내부에 묻었다. 스컬용융법에 의한 산화물 용융에서 매우 중요한 것은 융점에서의 전기 저항 값, RF generator의 주파수 그리고 냉각도가니 크기이다. 본 연구에서는, $TiO_2$의 융점에서의 전기저항$(10^{-2}\~10^{-1}\;{\Omega}{\cdot}m)$은 알루미나$(10^{-1}\;{\Omega}{\cdot}m)$의 지르코니아$(10^{-3}\;{\Omega}{\cdot}m)$의 전기저항 데이터를 바탕으로 추정하였다. 냉각도가니의 내부직경은 11cm, 높이는 14cm였으며, 이것은 침투깊이$(0.36\~1.13cm)$와 RF generator 주파수를 고려하여 결정하였다

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.126-129
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• 2009

In this study, it was aimed to develop the re-use technology of ultra-fine silicon powders, by-products during the current production process of high purity poly-Si feedstock. For this goal, the compacts of the silicon powders were tried to fabricate by CIP (Cold Isostatic Pressing) method using silicon rubber mold without chemical binder materials. The density ratio of the silicon powder compacts reached 74%. In order to simulate the actual handling and charging conditions of feedstock material in casting process, a shaking test was carried out and mass loss measured. Finally, the silicon powder compacts were melted using a cold crucible induction melting method and the purity assessment was conducted by Hall effect measurement.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1547-1554
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• 2017

VESTA (Verification of Ex-vessel corium STAbilization) and VESTA-S (-small) test facilities were constructed at the Korea Atomic Energy Research Institute in 2010 to perform various corium melt experiments. Since then, several tests have been performed for the verification of an ex-vessel core catcher design for the EU-APR1400. Ablation tests of an impinging $ZrO_2$ melt jet on a sacrificial material were performed to investigate the ablation characteristics. $ZrO_2$ melt in an amount of 65-70 kg was discharged onto a sacrificial material through a well-designed nozzle, after which the ablation depths were measured. Interaction tests between the metallic melt and sacrificial material were performed to investigate the interaction kinetics of the sacrificial material. Two types of melt were used: one is a metallic corium melt with Fe 46%, U 31%, Zr 16%, and Cr 7% (maximum possible content of U and Zr for C-40), and the other is a stainless steel (SUS304) melt. Metallic melt in an amount of 1.5-2.0 kg was delivered onto the sacrificial material, and the ablation depths were measured. Penetration tube failure tests were performed for an APR1400 equipped with 61 in-core instrumentation penetration nozzles and extended tubes at the reactor lower vessel. $ZrO_2$ melt was generated in a melting crucible and delivered down into an interaction crucible where the test specimen is installed. To evaluate the tube ejection mechanism, temperature distributions of the reactor bottom head and in-core instrumentation penetration were measured by a series of thermocouples embedded along the specimen. In addition, lower vessel failure tests for the Fukushima Daiichi nuclear power plant are being performed. As a first step, the configuration of the molten core in the plant was investigated by a melting and solidification experiment. Approximately 5 kg of a mixture, whose composition in terms of weight is $UO_2$ 60%, Zr 10%, $ZrO_2$ 15%, SUS304 14%, and $B_4C$ 1%, was melted in a cold crucible using an induction heating technique.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.357-360
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• 1997

Currently, there is a need for the development of an advanced new technology for Low-and Intermediate-Level Radioactive Waste (LILW) treatment from nuclear power plants. The vitrification and melting technology by the use of the electrical equipments such as induction heater and plasma torch based furnace, along with off-gas treatment are considered as the most promising one of the LILW treatment technology since they can produce a very stable waste forms as well as considerably large volume reduction, which is a world-wide trend to apply for radioactive waste treatment. Korea Electric Power Research Institute(KEPRI) has already completed a feasibility study on LILW treatment and conceptual system design of a demonstration plant to be constructed. For this research, KEPRI selected a cold crucible melter(CCM) for the vitrification of combustible waste, and plasma torch based furnace(PT) for the melting of noncombustible waste, along with off-gas treatment for the volatile radioisotopes such as cesium.

• Advances in materials Research
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• 제7권1호
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• pp.17-28
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• 2018

Niobium is a candidate base for new alloys devoted to applications at especially elevated temperatures. Elaborating and shaping niobium-based alloys by conventional foundry may lead to mechanically interesting microstructures. In this work a series of charges constituted of pure elements were subjected to high frequency induction melting in cold crucible to try obtaining cast highly refractory Nb-xCr and Nb-xCr-0.4 wt.%Calloys(x=27, 34 and 37 wt.%). Melting and solidification were successfully achieved. The as-cast microstructures of the obtained alloys were characterized by electron microscopy and X-ray diffraction and their hardness were specified by Vickers macro-indentation. The obtained as-cast microstructures are composed of a body centered cubic (bcc) niobium dendritic matrix and of an interdendritic eutectic compound involving the bcc Nb phase and a $NbCr_2$ Laves phase. The obtained alloys are hard to cut and particularly brittle at room temperature. Hardness is of a high level (higher than 600Hv) and is directly driven by the chromium content or the amount of {bcc Nb - $NbCr_2$} eutectic compound. Adding 0.4 wt.% of carbon did not lead to carbides but tends to increase hardness.

• 한국결정성장학회지
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• 제4권2호
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• pp.148-156
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• 1994

$YBa_2Cu_3O_X$상 부근의 3가지 조성을 skull melting 방법으로 4MHz에서 녹인 후 방향적 결정성장을 시켰다. 일반적인 무기재료 공정방법으로 처리된 분말을 skull에 넣은 후 $1200^{\circ}C$부근에서 용융시켰다. 사용한 성장속도는 4~0.25 cm/hr이었으며, 금속현미경, X-선 회절기, EDX 등을 이용해서 제조된 시편을 조사하여 사용한 분말의 조성에 따른 시편의 미세조직의 변화를 관찰하였다. $YBa_2Cu_7O_X$와 $YBa_5Cu_{11}O_X$ 시편의 대표적인 미세조직은 성장방향으로 자라난 침상형태의 $YBa_2Cu_3O_X$와 $Y_2BaCuO_5$ 상이 $CuO-BaCuO_2$의 공융 조직상 사이에 생성된 것으로 나타났다.