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Doda, Norihiro; Kato, Shinya; Iida, Masaki*; Yokoyama, Kenji; Tanaka, Masaaki
Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 8 Pages, 2022/10
In the conventional core design in sodium-cooled fast reactors (SFRs), negative reactivity feedback due to core deformation was neglected because of large uncertainty in analytical evaluation. To optimize core design, it is necessary to develop an analytical evaluation method and eliminate excessive conservativeness. An evaluation method for core deformation reactivity has been developed by coupling analysis of neutronics, thermal-hydraulics, and structural mechanics. For the verification study of the neutronics calculation method, the reactivity was calculated for the deformed core geometry in which the fuel assembly (FA) moved horizontally in the radial direction for each row from the core center. Compared to reference values derived from Monte Carlo calculations, the calculated reactivity due to FA displacement agreed well in the core region and was overestimated in the reflector region. The modification challenges in development of the core deformation model were identified.
Fukaya, Yuji; Goto, Minoru; Ohashi, Hirofumi
Annals of Nuclear Energy, 138, p.107182_1 - 107182_9, 2020/04
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)The investigation on self-shielding effect of double heterogeneity for plutonium burner High Temperature Gas-cooled Reactor (HTGR) design has been performed. Plutonium burner HTGR designed in the previous study by using the advantage of double heterogeneity to control excess reactivity. In the present study, the mechanism of the self-shielding effect is elucidated by the analysis of burn-up calculation and reactivity decomposition based on exact perturbation theory. As a result, it is revealed that the characteristics of burn-up reactivity are determined by resonance cross section peak at 1 eV of 
Pu due to the surface term of background cross section, this is, the characteristics of neutron leakage from fuel lump and collision to a moderator. Moreover, significant spectrum shift is caused during the burn-up period, and it enhances reactivity worth of 
Pu and Pu in EOL.
Yamamoto, Toshihiro; Miyoshi, Yoshinori
Nuclear Science and Engineering, 142(3), p.305 - 314, 2002/11
Times Cited Count：2 Percentile：16.96(Nuclear Science & Technology)Mechanisms of a positive temperature reactivity coefficient that occurs in a dilute plutonium solution are investigated based on the perturbation theory and the four-factor formula. The temperature coefficient of a solution fuel is positive if the adjoint flux or 
f between 0.05eV and 0.2eV increases with neutron energy. As compared to Pu-239, Pu-241 has a tendency to make the temperature coefficient of a plutonium solution. As Pu-241 in a plutonium solution decays into Am-241 with time, the temperature coefficient becomes more positive. Since the capture cross sections of most neutron absorbers such as boron and gadolinium decreases with increasing neutron energy, soluble absorbers make the temperature coefficient positive for higher concentration plutonium solution. Cadmium and samarium solved in a dilute plutonium solution exceptionally can keep the temperature coefficient. A fixed neutron absorber generally makes the temperature coefficient negative regardless of the property of absorber materials.
Fukushima, Masahiro; Suganuma, Hideo*; Chiba, Satoshi
Progress of Theoretical Physics, 107(6), p.1147 - 1161, 2002/06
Times Cited Count：1 Percentile：13.39(Physics, Multidisciplinary)Quantum Chromodynamics (QCD) is established as the standard theory of the strong interaction. Based on the lattice gauge theory, we investigate a deformation of stabilized instanton solutions in a nontrivial topological sector and further discuss appearance of monopole trajectories around the instanton.
Yamamoto, Toshihiro
Journal of Nuclear Science and Technology, 33(1), p.78 - 82, 1996/01
Times Cited Count：1 Percentile：14.44(Nuclear Science & Technology)no abstracts in English
coreYamamoto, Toshihiro
JAERI-M 93-170, 18 Pages, 1993/09
no abstracts in English
Takeda, Toshikazu*; Unesaki, Hironobu*; Kurisaka, Kenichi*; Sakuma, Hiroomi*; Shimoda, Masayuki*; Ito, Noboru*; Kugo, Teruhiko*; Aoki, Shigeaki*; Uto, Nariaki*; Tanaka, Motonari*
PNC TJ2605 88-001, 230 Pages, 1988/03
no abstracts in English
;
JAERI-M 7609, 28 Pages, 1978/03
no abstracts in English
;
JAERI-M 4760, 39 Pages, 1972/03
no abstracts in English
Sugino, Kazuteru; Numata, Kazuyuki; Ishikawa, Makoto; Takeda, Toshikazu*
no journal, ,
no abstracts in English
Maruyama, Shuhei; Endo, Tomohiro*; Yamamoto, Akio*
no journal, ,
no abstracts in English
