• 대한화학회지
• /
• 제35권6호
• /
• pp.699-706
• /
• 1991

헬륨 기체를 사용하여 중급 출력(500W) 마이크로파 유도 플라즈마(Microwave Induced Plasma:MIP)를 헬륨 기체를 사용하여 만든 뒤 직접 수용액 시료 분석에 사용하였다. Beenakker의 cavity를 변형시켜 얻은 안정된 헬륨 플라즈마는 실린더 형태의 모양을 하고 있고 기체의 흐름량을 조절하여 "toroidal"형태의 플라즈마도 얻을 수 있으나 분석학적 능력은 오히려 감소되었다. Glass Frit Nebuliser를 이용하여 분석하였을 때 금속 원소는 10~100 ppb 근처의 검출한계를 보였고 비금속원소인 염소의 경우는 50ppm근처의 검출한계를 보였다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
• /
• pp.104-104
• /
• 2015

Due to the demand of the cold neutron flux in the neutron science and beam utilization technology, the cold neutron source (CNS) has been constructed and operating in the nuclear research reactor all over the world. The majority of the heat load removal scheme in the CNS is two-phase thermosiphon using the liquid hydrogen as a moderator. The CNS moderates thermal neutrons through a cryogenic moderator, liquid hydrogen, into cold neutrons with the generation of the nuclear heat load. The liquid hydrogen in a moderator cell is evaporated for the removal of the generated heat load from the neutron moderation and flows upward into a heat exchanger, where the hydrogen gas is liquefied by the cryogenic helium gas supplied from a helium refrigeration system. The liquefied hydrogen flows down to the moderator cell. To keep the required liquid hydrogen stable in the moderator cell, the CNS consists of an in-pool assembly (IPA) connected with the hydrogen system to handle the required hydrogen gas, the vacuum system to create the thermal insulation, and the helium refrigeration system to provide the cooling capacity. If one of systems is running out of order, the operating research reactor shall be tripped because the integrity of the CNS-IPA is not secured under the full power operation of the reactor. To prevent unscheduled reactor shutdown during a long time because the research reactor has been operating with the multi-purposes, the introduction of the standby cooling system (STS) can be a solution. In this presentation, the design considerations are considered how to design the STS satisfied with the following objectives: (a) to keep the moderator cell less than 350 K during the full power operation of the reactor under loss of the vacuum, loss of the cooling power, loss of common electrical power, or loss of instrument air cases; (b) to circulate smoothly helium gas in the STS circulation loop; (c) to re-start-up the reactor within 1 hour after its trip to avoid the Xenon build-up because more than certain concentration of Xenon makes that the reactor cannot start-up again; (d) to minimize the possibility of the hydrogen-oxygen reaction in the hydrogen boundary.

• 대한기계학회논문집A
• /
• 제34권10호
• /
• pp.1455-1462
• /
• 2010

초고온가스로에서 생성된 $950^{\circ}C$ 정도의 초고온 열을 이용하여 수소를 경제적이며 또한 대량으로 생산하기 위한 시스템이 원자력수소생산시스템이며, 이 시스템에서 공정열교환기는 초고온 열과 황-요오드 공정을 통해 수소를 생산하는 핵심 기기이다. 한국원자력연구원에서는 초고온가스로에 사용될 기기에 대한 성능시험을 위해 헬륨가스루프를 구축하고 공정열교환기 시제품을 제작하였다. 본 연구는 공정열교환기 시제품을 헬륨가스루프에서 시험하기 전에 미리 공정열교환기 시제품의 고온 구조건전성을 평가하기 위한 작업의 일환으로 공정열교환기 시제품에 대한 고온구조해석 모델링, 열해석 및 열팽창해석 결과들을 정리한 것이다. 해석 결과는 공정열교환기 시제품 성능시험 장치 설계에 반영할 것이다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
• /
• pp.141-144
• /
• 2003

본 연구에서는 액체로켓의 극저온 추진제 공급부에서 요구되는 추진제의 공급 온도를 맞추기 위한 헬륨 가스 분사 냉각에 대한 수류 실험을 수행하여, 헬륨가스 분사에 의한 온도 저감에 대한 실험적 연구를 통한 온도 저감 특성을 고찰하였다. 수류 실험에 사용된 극저온 액체는 액체 질소를 사용하였으며, 냉각을 위한 가스로는 헬륨가스를 사용하였다. 헬륨 분사에 의한 액체 질소 과냉각 현상을 확인할 수 있었으며, v/v$_{L}$≒0.8$min^{-1}$ 조건에서 대략 4분 이내에 최대로 과냉각 (subcooling) 됨을 알 수 있었다.다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제21권4호
• /
• pp.372-380
• /
• 1997

This paper describes experimental investigations of helium-air exchange flows through parti¬tioned opening and two-opening. Such exchange flows may occur following rupture accident of stand pipe in high temperature gas cooled reactor. A test vessel with the two types of small open¬ing on top of test cylinder is used for experiments. An estimation method of mass increment is developed and applied to measure the exchange flow rate. A technique of flow visualization by Mach-Zehnder interferometer is provided to recognize the exchange flows. In the case of exchange flow through the partitioned opening, flow passages of upward flow of the helium and downward flow of the air within the opening are separated by vertical partition, and the two flows interact out of entrance and exit of the opening. Therefore, an experiment of the exchange flow through two-opening is made to investigate effect of the fluids interaction of the partitioned opening sys¬tem. As a result of comparison of the exchange flow rates between the two types of the opening system, it is found that the exchange flow rate of the two-opening system is larger than that of the partitioned opening system due to absence of the effect of fluids interaction. Finally, the fluids interaction between the upward and downward flows through the partitioned opening is found to be an important factor on the helium-air exchange flow.

• Corrosion Science and Technology
• /
• 제18권1호
• /
• pp.8-15
• /
• 2019

A high-temperature gas-cooled reactor (HTGR) is recognized as the best candidate reactor for next generation nuclear reactors. Helium is used to be the coolant in the core of the HTGR with temperature expected to exceed $900^{\circ}C$ at the core outlet. Several iron- and nickel-based superalloys, including Alloy 800H, Hastelloy X, and Alloy 617, are potential structural materials for intermediate heat exchanger (IHX) in an HTGR. Oxidation behaviors of three selected alloys (Hastelloy X, Alloy 800H, and Alloy 617) were investigated at four different temperatures from $650^{\circ}C$ to $950^{\circ}C$ under helium environments with various concentrations of $O_2$ and $H_2O$. Preliminary results showed that chromium oxide as the primary protective layer was observed on surfaces of the three tested alloys. Based on results of mass gain and SEM analyses, Hastelloy X alloy exhibited the best corrosion resistance in all corrosion tests. Further details on the oxidation mechanism of these alloys are presented in this study.

• Journal of Advanced Marine Engineering and Technology
• /
• 제40권3호
• /
• pp.157-164
• /
• 2016

본 연구에서는 SI 공정 시스템에서 헬륨 가열 장치에 대한 설계와 건조 데이터 확보를 위한 파이롯 규모의 헬륨 가열 장치 시스템에 대한 예비 설계 및 해석을 수행하였다. 헬륨 가열기는 LPG연소로를 활용하도록 설계하였고, 열유동 해석을 수행한 결과, 열교환기 출구측에서 LPG 연소가스의 유속이 약 40 m/s가 되었다. 최대온도는 6개의 베플이 설치된 경우가 4개의 베플이 설치된 경우보다 높게 나타나며, 이는 6개의 베플일 때 연소가스에서 헬륨가스로의 열전달이 좋아질 것임을 의미한다. 더불어, 베플수가 많아지면 LPG 연소가스의 유량을 감소시킬 수 있어 연료비용을 저감할 수도 있음을 의미한다. 다만, 베플수를 무한정 증가시키면 입출구의 압력차가 증가되기 때문에 최적의 베플수 선정이 중요하다. 열유동 해석에 이어 수행한 구조해석에서는 헬륨의 유량을 3.729 mol/s, 출구 온도를 $910^{\circ}C$로 유지할 경우 관의 양 끝단에서 지지하는 경우 중간부분의 팽창률이 3.86 mm임을 확인하였다. LPG 연소로 헬륨 가열시스템에서 shell & tube type의 열교환기를 적용하여 $135^{\circ}C$의 헬륨이 $910^{\circ}C$로 가열하여 유출하기 위해서 약 $1300^{\circ}C$의 연소가스 온도 및 52 g/s의 연소가스 유량이 확보되어야 함을 확인하였다.

• Journal of Welding and Joining
• /
• 제15권6호
• /
• pp.57-65
• /
• 1997

A study was undertaken to determine the influence of welding variables such as shielding and plasma gases, torch standoff, travel speed and heat input, etc. on the quality of plasma arc welds in Zircaloy-4 sheet, 2mm thick. Effect of shielding gases and their flow rates on the mechanical properties of Zircaloy-4 welds by plasma arc welding were determined in terms of tensile, bardness and bend tests. The microstructure and fracture surface of Zircaloy-4 welds were investigated by optical and scanning electron microscopies. In addition, the causes of porosity and undercut in plasma arc welds of Zircaloy-4 were also investigated. Zircaloy-4 weld bead width and depth by helium shielding gas showed a wider and deeper than those by argon. It was found that Zircaloy-4 welds with shielding gas of helium did dxhibit a little smoother and uniform weld beads than those with shielding gas of argon. It was also found that the optimum gas flow rates for Zircaloy-4 welding were 0.45l/min for plasma gas with Ar and 4.5 - 6 l/min for shielding gas with He. In addition, there was no big difference in the microstructure and fracture surface of the weld metals made by either Ar shielding gas or He shielding gas.

• 한국세라믹학회지
• /
• 제23권5호
• /
• pp.61-66
• /
• 1986

The gas mixtures ($H_2$/$N_2$, He/$N_2$) having a high thermal conductivity allow the heat generated by the nitriding exotherm to be dissipated from the compact in to the nitriding atmosphere permitting a more accurate control of temperature and produces a more uniform microstructure. In order to observe the effect of the mixed gas atmosphere on the microsturcture of RBSN. the specimen was nitrided in the mixed gas atmosphere which was containe up to 50vol% $H_2$ or He for 0-12 hrs at 135$0^{\circ}C$. The addition of hydrogen to nitrogen gas resulted in the growth of a-needle at the early stage of nitrding increase of the reaction rate and a finer and more uniform microstructure. in case of the addition of helium the behaviour of reaction was similar to the one with pure nitrogen. As the amount of helium was increased a coarse microstructure was formed.

• Nuclear Engineering and Technology
• /
• 제38권2호
• /
• pp.109-118
• /
• 2006

Various indirect power cycle options for a helium cooled gas cooled fast reactor (GFR) with particular focus on a supercritical $CO_2(SCO_2)$ indirect cycle are investigated as an alternative to a helium cooled direct cycle GFR. The balance of plant (BOP) options include helium-nitrogen Brayton cycle, supercritical water Rankine cycle, and $SCO_2$ recompression Brayton power cycle in three versions: (1) basic design with turbine inlet temperature of $550^{\circ}C$, (2) advanced design with turbine inlet temperature of $650^{\circ}C$ and (3) advanced design with the same turbine inlet temperature and reduced compressor inlet temperature. The indirect $SCO_2$ recompression cycle is found attractive since in addition to easier BOP maintenance it allows significant reduction of core outlet temperature, making design of the primary system easier while achieving very attractive efficiencies comparable to or slightly lower than, the efficiency of the reference GFR direct cycle design. In addition, the indirect cycle arrangement allows significant reduction of the GFR &proximate-containment& and the BOP for the $SCO_2$ cycle is very compact. Both these factors will lead to reduced capital cost.