• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2395-2407
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• 2022

The sodium-cooled fast reactor is among the innovative nuclear technologies selected in the framework of the development of Generation IV concepts, allowing the irradiation of uranium-plutonium mixed oxide fuels (MOX). A fundamental step for the safety assessment of MOX-fuelled pins for fast reactor applications is the evaluation, by means of fuel performance codes, of the integral thermal-mechanical behaviour under irradiation, involving the fission gas behaviour and release in the fuel-cladding gap. This work is dedicated to the performance analysis of an inner-core fuel pin representative of the ASTRID sodium-cooled concept design, selected as case study for the benchmark between the GERMINAL and TRANSURANUS fuel performance codes. The focus is on fission gas-related mechanisms and integral outcomes as predicted by means of the SCIANTIX module (allowing the physics-based treatment of inert gas behaviour and release) coupled to both fuel performance codes. The benchmark activity involves the application of both GERMINAL and TRANSURANUS in their "pre-INSPYRE" versions, i.e., adopting the state-of-the-art recommended correlations available in the codes, compared with the "post-INSPYRE" code results, obtained by implementing novel models for MOX fuel properties and phenomena (SCIANTIX included) developed in the framework of the INSPYRE H2020 Project. The SCIANTIX modelling includes the consideration of burst releases of the fission gas stored at the grain boundaries occurring during power transients of shutdown and start-up, whose effect on a fast reactor fuel concept is analysed. A clear need to further extend and validate the SCIANTIX module for application to fast reactor MOX emerges from this work; nevertheless, the GERMINAL-TRANSURANUS benchmark on the ASTRID case study highlights the achieved code capabilities for fast reactor conditions and paves the way towards the proper application of fuel performance codes to safety evaluations on Generation IV reactor concepts.

• 한국가스학회지
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• 제15권5호
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• pp.25-30
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• 2011

바이오가스는 Biomass, 유기성 폐기물 등의 혐기소화 공정을 통해 얻을 수 있는 대표적인 신재생연료로 저발열량에도 불구하고 탄소중립적인 특성이 있기 때문에 이를 엔진에 적용하여 에너지를 생산하고자 하는 노력이 계속되어왔다. 바이오가스는 원료의 종류 및 혐기소화 공정 조건에 따라 그 연료 조성이 달라질 수 있는데, 이러한 조성 변화는 엔진 성능에 큰 영향을 미칠 수 있기 때문에 이에 대한 연구가 필요한 실정이다. 따라서 이번 연구에서는 다양한 발열량을 갖는 바이오가스를 연료 내 불활성가스 비율을 변화시켜 모사하고 이를 이용하여 바이오가스 내 불활성가스 비율의 변화, 즉 발열량의 변화가 엔진 성능 및 배기 특성에 주는 영향을 파악하였다. 실험결과로 각 불활성가스 함량에 따른 최적 점화시기를 결정하였으며, 발열량 변화가 엔진 출력, 효율, 배기 성능에 미치는 영향을 제시하였다.

• 해양환경안전학회지
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• 제26권5호
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• pp.542-550
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• 2020

선박 및 해양구조물에서 사용하고 있는 고강도 알루미늄 합금들은 스틸과 비교해서 많은 이점을 가지고 있다. 최근 고강도 알루미늄 합금들은 육상 및 해양에 폭넓게 사용되고 있으며, 특히, 특수목적 선박의 선체 외판구조에 많이 이용되고 있고, 교량 구조물에 사용되는 상자 구조물, 그리고 고정식 해양플랫폼의 상부구조에서 소비율이 증가하고 있다. 알루미늄 재료는 스틸보다 1/3의 중량 구성비를 통하여, 구성 중량을 줄이게 하여 연비 절감을 가능하게 한다. 일반적인 강구조물의 응력-변형률 관계와 비교하면, 용접가공에 따라 발생하는 열영향부의 존재로 인하여 상당히 다르게 나타난다. 왜냐하면, 강구조물과 비교하면 열전도율이 높아서, 열영향부(heat affected zone, HAZ)가 남아 있어 구조 강도 저하를 가져온다. 본 논문에서는 MIG(Metal inert gas) 용접 때문에 발생하는 열영향부를 고려하고, 종방향 압축 하중에 대한 알루미늄 보강판의 좌굴 및 최종강도 특성을 분석하였다. MIG 용접에 따른 열영향부를 고려한 경우, 좌굴 및 최종강도 모두 감소하며, 열영향부의 범위가 15 mm부터 항복 이후 에너지 소실률이 크게 나타나며, 25 mm 이상부터는 그 차이가 크지 않다. 따라서, 알루미늄 합금재료를 적용한 보강판의 구조 거동을 파악하기 위해서는 열영향부 영향에 대한 검토 및 분석이 중요하다.

• 한국수소및신에너지학회논문집
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• 제24권1호
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• pp.44-49
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• 2013

Hydrogen penetration into a metal leads to damages and mechanical degradations and its content measurement is of importance. For a precise measurement, a sample preparation procedure must be optimized through a series of studies on sample washing and drying. In this study, two-step washing with organic solvents and thermal soaking in inert gas were tried with a rod-shaped, API X65 steel sample. The samples were machined from a steel plate and then washed in acetone and etyl-alcohol for 5 minute each and dried with compressed air. After then, the samples were thermally soaked in a home-made nitrogen gas chamber during 10 minute at different heat gun temperatures from 100 to $400^{\circ}C$ and corresponding temperature range in the soaking chamber was from 77 to $266^{\circ}C$ according to the temperature calibration. Hydrogen residue in the samples was measured with a hot extraction system after each soaking step; hydrogen residue of $0.70{\pm}0.12$ wppm after the thermal soaking at $77^{\circ}C$ decayed with increase of the soaking temperature. By adopting the heat transfer model, decay behavior of the hydrogen residue was fitted into an exponential decay function of the soaking temperature. Saturated value or lower bound of the hydrogen residue was 0.36 wppm and chamber temperature required to lower the hydrogen residue about 95% of the lower bound was $360^{\circ}C$. Furthermore, a thermal desorption spectroscopy was done for the fully soaked samples at $360^{\circ}C$. Weak hydrogen peak was observed for whole temperature range and it means that hydrogen-related contaminants of the sample surface are steadily removed by heating. In addition, a broad peak found around $400^{\circ}C$ means that parts of the hydrogen residue are irreversibly trapped in the steel microstructure.

• 한국분말재료학회지
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• 제17권3호
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• pp.190-196
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• 2010

In this paper, rapid solidified Mg-4.3Zn-0.7Y (at.%) alloy powders were prepared using an inert gas atomizer, followed by a severe plastic deformation technique of high pressure torsion (HPT) for consolidation of the powders. The gas atomized powders were almost spherical in shape, and grain size was as fine as less than $5\;{\mu}m$ due to rapid solidification. Plastic deformation responses during HPT were simulated using the finite element method, which shows in good agreement with the analytical solutions of a strain expression in torsion. Varying the HPT processing temperature from ambient to 473 K, the behavior of powder consolidation, matrix microstructural evolution and mechanical properties of the compacts was investigated. The gas atomized powders were deformed plastically as well as fully densified, resulting in effective grain size refinements and enhanced microhardness values.

• 반도체디스플레이기술학회지
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• 제20권4호
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• pp.157-160
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• 2021

As an insulator for a thin film transistor(TFT) and an encapsulation material of organic light emitting diode(OLED), aluminum oxide (Al₂O₃) has been widely studied using several technologies. Especially, in spite of low deposition rate, atomic layer deposition (ALD) has been used as a process method of Al₂O₃ because of its low process temperature and self-limiting reaction. In the Al₂O₃ deposition by ALD method, Ar Purge had some crucial effects on the film properties. After reaction gas is injected as a formation of pulse, an inert argon(Ar) purge gas is injected for gas desorption. Therefore, the process parameter of Ar purge gas has an influence on the ALD deposited film quality. In this study, Al₂O₃ was deposited on glass substrate at a different Ar purge time and its structural characteristics were investigated and analyzed. From the results, the growth rate of Al₂O₃ was decreased as the Ar purge time increases. The surface roughness was also reduced with increasing Ar purge time. In order to obtain the high quality Al₂O₃ film, it was known that Ar purge times longer than 15 sec was necessary resulting in the self-limiting reaction.

• 한국레이저가공학회지
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• 제17권2호
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• pp.5-10
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• 2014

Aluminum has been widely used in the electric applications because of light metals. When mechanical element is periodically moving with contacting other surfaces, the anodizing process for aluminum is useful for avoiding the abrasive damage. The anodized element has quietly different characteristics with respect to the distribution of hardness and crystal structure. In this work, the laser drilling of anodized surface is studied experimentally. Fusion drilling method - laser drilling with inert gas blowing - is used. The effect of various process parameters (gas pressure, laser power, focus position) is investigated with respect to the hole size and circularity.

• 한국세라믹학회지
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• 제44권1호
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• pp.37-42
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• 2007

The preparation of $TiC_{0.7}N_{0.3}$ powder by SHS in the system of $Ti-TiH_2-C$ ($N_2$ atmosphere) was investigated in this study. In the preparation of $TiC_{0.7}N_{0.3}$ powder, the effect of gas pressure, compositions such as Ti, $TiH_2$, C, and additive in mixture on the reactivity were investigated. At 50 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pure $TiC_{0.7}N_{0.3}$ was $0.75Ti+0.25TiH_2+0.7C+0.5NaCl$. The $TiC_{0.7}N_{0.3}$ powder synthesized in this condition was a single phase with irregular shape.

• Journal of Welding and Joining
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• 제23권3호
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• pp.54-60
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• 2005

Tungsten Inert Gas(TIG) welding is today one of the most popular arc welding process because of its high quality welds and low equipment costs. Even if welding productivity increases with welding speed and current, this strategy is limited by the appearance of defects such as undercut and humping bead due to the depressed molten metal. The purpose of this study investigates the effect of He mixing ratio on the characteristics with high current and speed in TIG welding. The conclusions obtained permit to explain the arc start characteristics quantitatively and the maximum welding speed on stable bead formation with He mixing ratio for high current and speed TIG welding observed in experiments. Also through the relation of the maximum arc pressure and surface depression depth at high current and speed TIG welding, it made clear the mechanism of unstable bead formation.

• 한국화재소방학회논문지
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• 제12권2호
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• pp.61-68
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• 1998

가축사료 분진의 열적 안정성 실험결과 본 연구에서 사용한 시료 입도의 경우 발열개시온도 및 발열 량에는 별 차이가 없었으나, 숭온속도가 충가함에 따라 발열개시온도가 낮아지고, 입도가 미세해질수 록 분해열이 증가함을 알 수 있었다. 한편, 분위기 기체룰 조연성 기체인 Oz로 사용할 경우 불활성 기 체인 Nz를 사용하는 경우보다 발열개시온도는 현저히 낮아지며, 반면에 발열량도 20배 이상 중가하였 다. 또한 본 연구에서 사용한 시료중 비교적 미세업자가 대기중에 부유하기 쉽고, 외부에서 점화에너지 가 주어질 경우 공기중의 산소와 쉽게 순간적으로 반용하여 폭발하는 것올 볼 수 있다. 본 연구에서의 시료입도중 80/100 mesh의 경우 평균 최대폭발압력은 6.88 Kgf / cm2 로 구해졌다.