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Transmutation of Nuclear Waste with a Low-aspect-ratio Tokamak Neutron Source
홍봉근,문세연 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.8
The transmutation characteristics of transuranics (TRUs) in a transmutation reactor based on aLAR (Low-aspect-ratio) tokamak as a neutron source are investigated. The optimum radial buildof a transmutation reactor is found by using a coupled analysis of the tokamak systems and theneutron transport. The dependences of the transmutation characteristics on the aspect ratio A inthe range of 1.5 to 2.5 and on the fusion power in the range of 150 to 500 MW are investigated. An equilibrium fuel cycle is developed for effective transmutation, and show that with one unit ofthe transmutation reactor based on the LAR tokamak producing fusion power in the range of a fewhundred MWs, up to 3 PWRs (1.0 GWe capacity) can be supported with a burn-up fraction largerthan 50%.
홍봉근(Bong Guen Hong) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12
우주용 내열재료 삭마 시험을 위한 초음속 고엔탈피 플라즈마 풍동이 전북대학교 고온플라즈마응용 연구센터에 구축되었다. 구축이 완료된 플라즈마 풍동은 0.4㎿ 및 2.4㎿급 플라즈마 풍동이며 본 논문에서는 2가지 형태의 플라즈마 풍동의 운전 특성을 확인하였다. 0.4㎿급 플라즈마 풍동의 경우 공기 아르곤 혼합기체 16 g/s를 이용하여 13 MJ/㎏의 엔탈피를 갖는 유체를 마하3 속도로 안정적으로 가속시키는 것을 확인하였고 2.4㎿급 플라즈마 풍동의 경우 공기 아르곤 혼합기체 60 g/s를 이용하여 20 MJ/㎏의 엔탈피를 갖는 유체를 마하5의 속도로 가속 가능한 것이 확인되어 향후 우주용 내열재료 시험 및 열 방어 구조 설계를 위한 토대가 마련되었다. Supersonic high enthalpy plasma wind tunnel has been constructed at Chonbuk National University(CBNU). The facilities are 1 set of 2.4 ㎿ class wind tunnel and 1 set of 2.4 ㎿ calss wind tunnel. The segmented arc plasma torch was employed as a plasma source, and it can produce a supersonic high enthalpy flow with enthalpy above 13 MJ/㎏ at a velocity of Mach No. 3 and with enthalpy above 20 MJ/㎏ at a velocity of Mach No. 5.
서준호,홍봉근,최수석,김동욱 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.2
As a high-powered plasma source to produce a specific enthalpy higher than 20 MJ/kg at an air flow rate of 50 g/s for a supersonic plasma wind tunnel, a segmented-type arc plasma torch with an input power level of MW class is characterized in this paper. For this purpose, a numerical parametric study was carried out to determine the main design parameters, such as, the constrictor length <i>L<sub>C</sub></i>, the diameter of segmented disk <i>D<sub>C</sub></i>, and the diameter of the electrode <i>D<sub>E</sub></i>, under the requirements of specific enthalpy and air flow rate. From the results of the numerical study, firstly the plasma power and specific enthalpy are found to increase with increasing <i>L<sub>C</sub></i> at the expense of the torch efficiency, which is defined as the ratio of the total exit enthalpy to the plasma power. On the other hand, an increase in <i>D<sub>C</sub></i> is observed to improve the torch efficiency by reducing the plasma power at a fixed arc current and gas flow rate. Moreover, an increase in <i>D<sub>E</sub></i> is also found to contribute to improvements in the torch efficiency and the specific enthalpy by expanding the high-temperature region of the arc plasma and decreasing plasma velocities at the torch exit. Accordingly, a scale up to MW class for obtaining a high specific enthalpy can be achieved efficiently by inserting segmented disks with relatively large diameters between enlarged electrodes and then increasing the arc currents. For example, if the length of a constrictor consisting of segmented disks with a diameter of <i>D<sub>C</sub></i> = 25 mm is extended to <i>L<sub>C</sub></i> = 900 mm and then the arc current is increased up to 800 A, it is predicted that a specific enthalpy of 21.2 MJ/kg can be achieved at a plasma power of 2.89 MW and an air flow rate of 50 g/s, which corresponds to a torch efficiency of 36.6% Based on these numerical parametric study results, we expect that a segmented arc plasma torch can be designed to meet the requirements of a supersonic plasma wind tunnel, such as a specific enthalpy, air flow rate and plasma power.
고주파 열플라즈마 토치를 이용한 Ni 금속 입자의 나노화 공정에 대한 전산해석 연구
남준석,홍봉근,서준호,Nam, Jun Seok,Hong, Bong-Guen,Seo, Jun-Ho 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.5
Numerical analysis on RF (Radio-Frequency) thermal plasma treatment of micro-sized Ni metal was carried out to understand the synthesis mechanism of nano-sized Ni powder by RF thermal plasma. For this purpose, the behaviors of Ni metal particles injected into RF plasma torch were investigated according to their diameters ($1{\sim}100{\mu}m$), RF input power (6 ~ 12 kW) and the flow rates of carrier gases (2 and 5 slpm). From the numerical results, it is predicted firstly that the velocities of carrier gases need to be minimized because the strong injection of carrier gas can cool down the central column of RF thermal plasma significantly, which is used as a main path for RF thermal plasma treatment of micro-sized Ni metal. In addition, the residence time of the injected particles in the high temperature region of RF thermal plasma is found to be also reduced in proportion to the flow rate of the carrier gas In spite of these effects of carrier gas velocities, however, calculation results show that a Ni metal particle even with the diameter of $100{\mu}m$ can be completely evaporated at relatively low power level of 10 kW during its flight of RF thermal plasma torch (< 10 ms) due to the relatively low melting point and high thermal conductivity. Based on these observations, nano-sized Ni metal powders are expected to be produced efficiently by a simple treatment of micro-sized Ni metal using RF thermal plasmas.
THERMAL PLASMA SYNTHESIS OF NANO-SIZED POWDERS
서준호,홍봉근 한국원자력학회 2012 Nuclear Engineering and Technology Vol.44 No.1
A brief review on the thermal plasma synthesis of nano-sized powders is presented according to the application materials,such as, metals, ceramics, glasses, carbonaceous materials and other functional composites, such as, supported metal catalyst and core-shell structured nano materials. As widely adopted plasma sources available for thermal plasma synthesis of nanosized powders, three kinds of plasma torches, such as transferred and non-transferred DC and RF plasma torches, are introduced with the main features of each torch system. In the basis of the described torch features and the properties of suggested materials, application results including synthesis mechanism are reviewed in this paper.