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Öğe Elimination of the coil shielding for MFE-reactors through a liquid-protected first-wall(King Fahd Univ Petroleum Minerals, 2002) Sahin, S; Sahinaslan, A; Sahin, HMThe idea of a protective, flowing, liquid zone to protect the first wall of a magnetic fusion energy (MFE) reactor from the direct exposure of the fusion reaction products is not new. This could extend the lifetime of the first wall to the lifetime of the fusion power plant, namely to 30 years. The present work discusses the possibility that such a liquid zone could lead also to the elimination of the magnetic coil shielding for WE reactors. Contrary to a related previous work, the liquid wall is now placed at the outermost periphery of the plasma chamber, in order to leave a greater space for the fusion plasma volume and consequently to lead to higher fusion power with the same plasma parameters. In this work, SS-304 type steel, SiC, and graphite are selected as structural materials. Different types of liquid coolant with tritium breeding capabilities (Flibe, Li17Pb83, natural lithium, all with natural lithium component) are investigated to protect the first wall from neutron- and bremsstrahlung-radiation and fusion reaction debris. The calculations are conducted for a power generation of 1GW(el) over 30 years of reactor operation with a thermodynamically conversion efficiency of 35 % leading to 2.857 GW(th) by a capacity factor of 100 %, The most important improvements through the placement of the protective liquid wall at the outer periphery in the new blanket can be cited as follows. Such a blanket: would in practice not necessitate extra shielding for superconducting coils around the fusion plasma chamber; would open the possibility of utilization of conventional stainless steel for fusion reactors due to the sufficiently low residual radioactivity in the structural materials after decommissioning of the plant. Research efforts and costs, involved in searching new alternative ceramic structural materials, such as SiC and graphite, based on unproven technology can be saved; and would make it possible to produce higher fusion power with a greater plasma volume.Öğe Enhancement of solar thermal energy storage performance using sodium thiosulfate pentahydrate of a conventional solar water-heating system(Elsevier Science Sa, 2005) Canbazoglu, S; Sahinaslan, A; Ekmekyapar, A; Aksoy, IG; Akarsu, FThe time variations of the water temperatures at the midpoint of the heat storage tank and at the outlet of the collector in a conventional open-loop passive solar water-heating system combined with sodium thiosulfate pentahydrate-phase change material (PCM) were experimentally investigated during November and then enhancement of solar thermal energy storage performance of the system by comparing with those of conventional system including no PCM was observed. It was observed that the water temperature at the midpoint of the storage tank decreased regularly by day until the phase-change temperature of PCM after the intensity of solar radiation decreased and then it was a constant value of 45 degreesC in a time period of approximately 10 h during the night until the sun shines because no hot water is used. Heat storage performances of the same solar water-heating system combined with the other salt hydrates-PCMs such as zinc nitrate hexahydrate, disodium hydrogen phosphate dodecahydrate, calcium chloride hexahydrate and sodium sulfate decahydrate (Glauber's salt) were examined theoretically by using meteorological data and thermophysical properties of PCMs with some assumptions. It was obtained that the storage time of hot water, the produced hot water mass and total heat accumulated in the solar water-heating system having the heat storage tank combined with PCM were approximately 2.59-3.45 times of that in the conventional solar water-heating system. It was also found that the hydrated salts of the highest solar thermal energy storage performance in PCMs used in theoretical investigation were disodium hydrogen phosphate dodecahydrate and sodium sulfate decahydrate. (C) 2004 Elsevier B.V. All rights reserved.Öğe Neutron and gamma ray heating in the grazing incident liquid metal mirrors for laser inertial fusion energy power plants(Pergamon-Elsevier Science Ltd, 2002) Sahin, S; Sahinaslan, AA thin film of liquid metal can serve as final optics of a laser inertial fusion energy (IFE) power plant. Calculations of pulsed neutron and gamma-ray heating are presented for a grazing incident liquid metal mirror (GILMM) used for robust final optics of a laser IFE power plant. Different liquid films (Li, Na, Mg, Al, Si, K, Ga, Ag, Au, Pb, Bi and Flibe Li2BeF4) are considered at a distance of 30 in from a nominal 1 GJ fusion source as well as different substrate materials (SS-304 and SiC). The effect of neutron heating both in the liquid metal film as well as in the subsrate material will be by around three to four orders of magnitude lower than the laser heating limit. Hence the nuclear heating will not be a limiting factor for grazing incident liquid metal mirror (GILMM) of a laser IFE power plant. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe Reduced shielding mass for the VISTA spacecraft(Springer Heidelberg, 2002) Sahin, S; Sahin, HM; Sahinaslan, AAn innovative concept for the direct utilization of fusion energy with laser ignited (D,T) capsules for propulsion is presented with the so called VISTA (Vehicle for Interplanetary Space Transport Applications) concept. VISTA's overall geometry is that of a 50degrees-half-angle cone to avoid massive radioactive shielding. The 50degrees-half-angle maximizes the jet efficiency, and is determined by selecting the optimum pellet firing position along the axis of the cone with respect to the plane of the magnet coil. The pellet firing position is in the vacuum. Assuming a total fusion power production of 17 500 MW with a repetition rate of 5 Hz and 3500 MJ per shot, the propulsion power in form of charged particles has been calculated as similar to7000 MW, making similar to40% of the total fusion power. About 60% of the fusion energy is carried by the leaking neutrons out of the pellet. Most of them (96%) escape into vacuum without striking the space ship. Only 4% enter the frozen hydrogen expellant in the conical shape (about 50 gr.). Two design limits are discussed, 5 and 1 mW/cm(3). Total peak nuclear heat generation in the coils is calculated as 4.7 mW/cm(3). The peak neutron heating is 1.9 mW/cm(3) and the peak gamma-ray heating density is 2.8 mW/cm(3). However, volume averaged nuclear heat generation in the coils is much lower. It is calculated as 0.18, 0.48, and 0.66 mW/cm(3) for neutron, gamma-ray, and total nuclear heating, respectively. With higher design limits for nuclear heat generation in the coils and using natural lithium in the shielding, it was possible to reduce the net shielding mass from 595 tonne down to 170 tonne, making <3% of the vehicle mass, by a total vehicle mass of VISTA similar to 6 000 tonne.
