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Tonoike, Kotaro; Okubo, Kiyoshi; Takada, Tomoyuki*
Proceedings of International Conference on Nuclear Criticality Safety (ICNC 2015) (DVD-ROM), p.292 - 300, 2015/09
The damaged Unit 1-3 reactors of the Fukushima Daiichi Nuclear Power Station may contain fuel debris of a significant amount that is in a form of molten-core-concrete-interaction (MCCI) product with porous structure. Such low density MCCI product including fissile material is a great concern for its criticality control, especially under submerged condition, due to its fairly good neutron moderation. This report shows computation results of basic criticality characteristics of the MCCI product, which will facilitate criticality risk assessments during decommissioning of the reactors. The results imply that water bound in concrete may raise the risk from the viewpoints of possibility of criticality events and of effectiveness of mitigation measures such as neutron poison injection into coolant water.
m band using focused proton beamMiura, Kenta*; Machida, Yuki*; Uehara, Masato*; Kiryu, Hiromu*; Ozawa, Yusuke*; Sasaki, Tomoyuki*; Hanaizumi, Osamu*; Sato, Takahiro; Ishii, Yasuyuki; Koka, Masashi; et al.
Key Engineering Materials, 497, p.147 - 150, 2012/00
Times Cited Count：7 Percentile：94.42(Engineering, Electrical & Electronic)m band using focused proton beamMiura, Kenta*; Machida, Yuki*; Uehara, Masato*; Kiryu, Hiromu*; Ozawa, Yusuke*; Sasaki, Tomoyuki*; Hanaizumi, Osamu*; Sato, Takahiro; Ishii, Yasuyuki; Koka, Masashi; et al.
Key Engineering Materials, 497, p.147 - 150, 2011/12
Times Cited Count：6 Percentile：2.48Suyama, Kenya; Mochizuki, Hiroki*; Takada, Tomoyuki*; Ryufuku, Susumu*; Okuno, Hiroshi; Murazaki, Minoru; Okubo, Kiyoshi
JAEA-Data/Code 2009-002, 124 Pages, 2009/05
JAEA-Data-Code-2009-002.pdf:14.09MB
Integrated burnup calculation code system SWAT is a system that combines neutronics calculation code SRAC widely used in Japan and point burnup calculation code ORIGEN2. It has been used to evaluate the composition of the uranium, plutonium, minor actinide and the fission products in the spent nuclear fuel. Because of the ability to treat the arbitrary fuel geometry and no requirement of generating the effective cross section data, there is a great advantage to introduce continuous energy Monte Carlo Code into the burnup calculation code. Based on this idea, the integrated burnup calculation code system SWAT3.1 was developed by combining the continuous energy Monte Carlo code MVP and MCNP and ORIGEN2. This report describes the outline, input data instruction and several example of the calculation.
RhGa
and UFeGaIkeda, Shugo; Okubo, Tomoyuki*; Inada, Yoshihiko*; Tokiwa, Yoshifumi; Kaneko, Koji; Matsuda, Tatsuma; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika
Journal of Physics; Condensed Matter, 15(28), p.S2015 - S2018, 2003/07
Times Cited Count：6 Percentile：34.94(Physics, Condensed Matter)no abstracts in English
(T:Fe, Co and Pt)Ikeda, Shugo; Tokiwa, Yoshifumi*; Okubo, Tomoyuki*; Yamada, Mineko*; Matsuda, Tatsuma; Inada, Yoshihiko*; Settai, Rikio*; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika
Physica B; Condensed Matter, 329-333(2), p.610 - 611, 2003/05
Times Cited Count：13 Percentile：55.29(Physics, Condensed Matter)no abstracts in English
Ikeda, Shugo; Tokiwa, Yoshifumi*; Haga, Yoshinori; Yamamoto, Etsuji; Okubo, Tomoyuki*; Yamada, Mineko*; Nakamura, Noriko*; Sugiyama, Kiyohiro*; Kindo, Koichi*; Inada, Yoshihiko*; et al.
Journal of the Physical Society of Japan, 72(3), p.576 - 581, 2003/03
Times Cited Count：41 Percentile：82.19(Physics, Multidisciplinary)no abstracts in English
Matsuda, Tatsuma; Haga, Yoshinori; Tokiwa, Yoshifumi; Andrei, G.; Yamamoto, Etsuji; Okubo, Tomoyuki*; Onuki, Yoshichika
Acta Physica Polonica B, 34(2), p.1071 - 1074, 2003/02
We have successfully grown a single crystal of uranium intermetallic compound URhGe. The temperature dependence of electrical resistivity shows highly anisotropic behavior. Two anomalies, which correspond to the magnetic ordering temperatures, were observed in the resistivity, magnetic susceptibility and specific heat measurements at 
= 30 K and 
=25 K. The magnetic susceptibility also shows a large uniaxial anisotropy with a magnetic easy-axis along the [010] direction.
SiMatsuda, Tatsuma; Metoki, Naoto; Haga, Yoshinori; Ikeda, Shugo; Okubo, Tomoyuki*; Sugiyama, Kiyohiro*; Nakamura, Noriko*; Kindo, Koichi*; Kaneko, Koji; Nakamura, Akio; et al.
Journal of the Physical Society of Japan, 72(1), p.122 - 130, 2003/01
Times Cited Count：13 Percentile：60.61(Physics, Multidisciplinary)no abstracts in English
SiMatsuda, Tatsuma; Haga, Yoshinori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Ikeda, Shugo; Okubo, Tomoyuki*; Yamada, Mineko*; Nakamura, Akio; Onuki, Yoshichika
Journal of Nuclear Science and Technology, 39(Suppl.3), p.225 - 228, 2002/11
no abstracts in English
Tokiwa, Yoshifumi; Ikeda, Shugo*; Haga, Yoshinori; Okubo, Tomoyuki*; Iizuka, Tomoya*; Sugiyama, Kiyohiro*; Nakamura, Akio; Onuki, Yoshichika
Journal of the Physical Society of Japan, 71(3), p.845 - 851, 2002/03
no abstracts in English
Tokiwa, Yoshifumi; Ikeda, Shugo*; Haga, Yoshinori; Okubo, Tomoyuki*; Iizuka, Tomoya*; Sugiyama, Kiyohiro*; Nakamura, Akio; Onuki, Yoshichika
Journal of the Physical Society of Japan, 71(3), p.845 - 851, 2002/03
Times Cited Count：40 Percentile：80.77(Physics, Multidisciplinary)We succeeded in growing a high-quality single crystal of an antiferromagnet UPtGa by the self-flux method, and measured the magnetic susceptibility, electrical resistivity, specific heat and de Haas-van Alphen (dHvA) oscillation. We found an antiferromagnetic transition at 26K from the magnetic susceptibility and electrical resistivity measurements. Six dHvA branches were observed, ranging from 1.14
10
to 1.1310
Oe. Fermi surfaces consist of two nearly cylindrical and two spherical Fermi surfaces. The cyclotron mass is large, ranging from 10 to 24 
, which is consistent with the electronic specific heat coefficient 
= 57 mJ/K
mol.
Miura, Kenta*; Sato, Takahiro; Ishii, Yasuyuki; Koka, Masashi; Machida, Yuki*; Uehara, Masato*; Kiryu, Hiromu*; Takano, Katsuyoshi*; Okubo, Takeru; Yamazaki, Akiyoshi; et al.
no journal, ,
Kawashima, Katsuyuki; Uwaba, Tomoyuki; Okubo, Tsutomu; Mizuno, Tomoyasu; Nemoto, Junichi*
no journal, ,
In the frame of the Fast Reactor Cycle Technology Development (FaCT) project, the sodium-cooled fast reactor core transient analysis models are considered by focusing on the power skewing effect on the TOP fuel temperature. It is shown that the considerations of the power skewing increase the average fuel temperature rise leading to more negative reactivity feedback during TOP.
Tonoike, Kotaro; Okubo, Kiyoshi; Takada, Tomoyuki*
no journal, ,
no abstracts in English
Okubo, Kiyoshi; Suyama, Kenya; Kashima, Takao; Tonoike, Kotaro; Takada, Tomoyuki*
no journal, ,
Criticality safety analysis is necessary for the damaged-fuel handling in the Fukushima Daiichi NPP decommissioning. This presentation show influence of structural materials such as Zry-2, Fe, concrete expected to be present in the damaged fuel. Multiplication factor (kinf) decreases most by replacing moisture, in the damaged fuel, with iron. Replacement of all moisture with Zry-2 gives the same influence as iron, although decrease rate of kinf is lower because of the smaller absorb cross section of Zry-2. Concrete has much less influence due to the neutron moderation by hydrogen contained in concrete, which calls attention on handling of the concrete-fuel mixture. Effect as reflector of the materials is also evaluated.
