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Tobita, Kenji; Nishio, Satoshi*; Enoeda, Mikio; Nakamura, Hirofumi; Hayashi, Takumi; Asakura, Nobuyuki; Uto, Hiroyasu; Tanigawa, Hiroyasu; Nishitani, Takeo; Isono, Takaaki; et al.
JAEA-Research 2010-019, 194 Pages, 2010/08
JAEA-Research-2010-019-01.pdf:48.47MBJAEA-Research-2010-019-02.pdf:19.4MB
This report describes the results of the conceptual design study of the SlimCS fusion DEMO reactor aiming at demonstrating fusion power production in a plant scale and allowing to assess the economic prospects of a fusion power plant. The design study has focused on a compact and low aspect ratio tokamak reactor concept with a reduced-sized central solenoid, which is novel compared with previous tokamak reactor concept such as SSTR (Steady State Tokamak Reactor). The reactor has the main parameters of a major radius of 5.5 m, aspect ratio of 2.6, elongation of 2.0, normalized beta of 4.3, fusion out put of 2.95 GW and average neutron wall load of 3 MW/m
. This report covers various aspects of design study including systemic design, physics design, torus configuration, blanket, superconducting magnet, maintenance and building, which were carried out increase the engineering feasibility of the concept.
Asakura, Koichi; Takeuchi, Kentaro; Makino, Takayoshi; Kato, Yoshiyuki
Nuclear Technology, 167(3), p.348 - 361, 2009/09
Times Cited Count：4 Percentile：30.49(Nuclear Science & Technology)Technological feasibility of a simplified MOX pellet fabrication process, the short process, was studied. About 300 g MH-MOX powder with adjusted plutonium content to 30% could be successfully processed by a tumbling-granulator for subsequent pelletizing and sintering processes. The granulated 30%PuO
-MOX powder could be pressed into green annular pellets directly and smoothly when using a die wall lubrication method. The pellet tensile strengths were compared for a granulated molybdenum powder and they were higher for pellets obtained when using the die wall lubrication method than when using the conventional powder mixing method. The amount of additives in the green pellets could be controlled at 0.06wt% in this process. It is therefore, possible to carry out de-waxing and sintering of green pellets in the same furnace. By controlling the average particle sizes of granulated 30%PuO-MOX powders, pellets with more than 95% theoretical density could be obtained after 1700 
C for 2 h. As a result, it can be concluded that the short process is technoligically feasible to fabricate MOX annular pellets.
Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Kawashima, Hisato; Kurita, Genichi; Tanigawa, Hiroyasu; Nakamura, Hirofumi; Honda, Mitsuru; Saito, Ai*; Sato, Satoshi; et al.
Nuclear Fusion, 49(7), p.075029_1 - 075029_10, 2009/07
Times Cited Count：137 Percentile：97.72(Physics, Fluids & Plasmas)Recent design study on SlimCS focused mainly on the torus configuration including blanket, divertor, materials and maintenance scheme. For vertical stability of elongated plasma and high beta access, a sector-wide conducting shell is arranged in between replaceable and permanent blanket. The reactor adopts pressurized-water-cooled solid breeding blanket. Compared with the previous advanced concept with supercritical water, the design options satisfying tritium self-sufficiency are relatively scarce. Considered divertor technology and materials, an allowable heat load to the divertor plate should be 8 MW/m or lower, which can be a critical constraint for determining a handling power of DEMO (a combination of alpha heating power and external input power for current drive).
Asakura, Koichi; Kato, Yoshiyuki; Furuya, Hirotaka
Nuclear Technology, 162(3), p.265 - 275, 2008/06
Times Cited Count：9 Percentile：52.81(Nuclear Science & Technology)UO, PuO and MOX (mixed oxide of U and Pu) powders were prepared by the MH (microwave heating de-nitration), ADU (Ammonia diuranate) and OX (oxalate) methods. The BET specific surface area, avarage particle size by air permiation method, bulk density, tap density, angle of repose, angle of spatula and cohesiveness of these powders were measured. The degree of surface roughness was evaluated from the ratio of BET surface area to the one calculated from average particle size and then flowability was evaluated on the basis of Carr's theory. These results were compared for the different powders and preperation methods as a parameter of calcination temperature. The degree of surface roughness in MH-MOX powder was larger than in ADU-UO powder and smaller in OX-PuO powder. These results could be understood using the concpt of H
ttig and Tamman temperatures commonly cited in ceramics materials. As already reported for the general papers, the flowabilities of MH-MOX and ADU-UO powders also decreased with increase of compressibility, and their absolute values were below 50 points. According to Carr's theory, the brderline between free-flowing and non-free-flowing powders is from 60 to 69 points. It is, therefore, necessary for the mixed powder of MH-MOX powder, ADU-UO powder and dry recycled MOX scrap powder to be granulated to provide a free flowing feed to the pelletizing press in the MOX pellet fabrication process.
Asakura, Koichi; Yamaguchi, Toshihiro; Otani, Tetsuo
Journal of Nuclear Materials, 357(1-3), p.126 - 137, 2006/10
Times Cited Count：9 Percentile：53.38(Materials Science, Multidisciplinary)The fabrication of low density MOX pellets was studied using some organic compounds as pore formers. The pore former, K3 showed the best performance among five organic compounds in the 7.5 kg-UOX runs, but K3 lost this in 36 kg-MOX run, possibly because plutonium decay heat affected its performance. Comparison of thermal stubilities between K3 and a newly introduced pore former, Avicel, of high softening temperature, showed that K3 lost its spherical particle shape and consequently, its pore forming ability at 70C which was below its reported melting point (84-88C) while Avicel could maintain its spherical particle shape up to 150C. The pore forming performance of Avicel was also comfirmed in the 36 kg-MOX run which is the same scale as for mass production of MOX fuel pellets.
Asakura, Koichi; Takeuchi, Kentaro
Journal of Nuclear Materials, 348(1-2), p.163 - 173, 2006/01
Times Cited Count：12 Percentile：63.1(Materials Science, Multidisciplinary)Sintering behavior of MOX compacts containing defferent amounts of carbon (290 to 1,735 ppm) was investigated at temperatures from 1,073 to 2,023 K to study the effect of residual carbon. Specimen shrinkages were measured with a non-contact type optical dilatmeter during heating. The compact shrinkage from 1,273 to 1,523 K was about 6 times larger in the two spcimens with high residual carbon content than in the two specimens with low residual content. This behavior could be understood by considering that shrinkage of former specimens was enhanced in this temperature range by the decrease of O/M ratio due to the evolution of CO gas and consequently the significant increase of the metal ion inter-diffusion conefficient. In the specimens with low residual carbon content, the amount of CO gas evolution was too small to affect the inter-diffusion coefficient. This differece in shrinkage between the two kinds of specimens was also discussed from a theoretical model applied to the initial sintering stage of ceramics.
Kobayashi, Hideo; Asakura, Koichi
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Asakura, Koichi
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Asakura, Koichi
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Okita, Takatoshi; Sudo, Katsuo; Kihara, Yoshiyuki; Asakura, Koichi; Ojima, Hisao
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Ojima, Hisao; Ito, Masanori; Takahashi, Saburo; Asakura, Koichi; Aoki, Yoshikazu
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