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Kawano, Takahiro*; Mizuta, Naoki; Ueta, Shohei; Tachibana, Yukio; Yoshida, Katsumi*
JAEA-Technology 2023-014, 37 Pages, 2023/08
JAEA-Technology-2023-014.pdf:2.35MB
Fuel compact for High Temperature Gas-cooled Reactor (HTGR) is fabricated by calcinating a matrix consisting of graphite and binder with the coated fuel particle. The SiC-matrixed fuel compact uses a new matrix made of silicon carbide (SiC) replacing the conventional graphite. Applying the SiC-matrixed fuel compact for HTGRs is expected to improve their performance such as power densities. In this study, the sintering conditions for applying SiC as the matrix of fuel compacts for HTGR are selected, and the density and thermal conductivity of the prototype SiC are measured.
Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Times Cited Count：43 Percentile：96.93(Astronomy & Astrophysics)Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 
C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.
High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02
As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.
Koura, Hiroyuki; Yoshida, Tadashi*; Tachibana, Takahiro*; Chiba, Satoshi*
JAEA-Conf 2017-001, p.205 - 210, 2018/01
no abstracts in English
Koura, Hiroyuki; Yoshida, Tadashi*; Tachibana, Takahiro*; Chiba, Satoshi*
EPJ Web of Conferences, 146, p.12003_1 - 12003_4, 2017/09
Times Cited Count：3 Percentile：86.43(Nuclear Science & Technology)Koura, Hiroyuki; Katakura, Junichi*; Tachibana, Takahiro*; Minato, Futoshi
JAEA-Conf 2015-003, p.147 - 152, 2016/03
A chart of the nuclides 2014 version is now preparing to be published from JAEA. This will be the latest successive version of the chart since 1977, and continues every (approximately) four years until 2010. These charts include decay data of isotopes as half-lives, decay modes, and some isomeric states. In addition, the periodic table of elements, fundamental physical constants, thermal neutron capture and fission cross sections are tabulated. The latest version is now compiled with recent experimental data until the end of June in 2014. In the compilation process, we improved in the following parts: (1) Neutron or proton-unbound nuclei in the lighter region. (2) Drawing the neutron and proton-drip lines, and a boundary line of 
-delayed neutron emission. (3) 1- or 2-proton-emission theoretical half-lives are added for unmeasured nuclei in addition to original three partial half-lives of 
-decay, -decay and spontaneous fission. We compiled totally 3150 nuclides, which were experimental identified including 2914 life-measured nuclei. We will show overview of the chart with some statistics and examples.
Koura, Hiroyuki; Tachibana, Takahiro*; Chiba, Satoshi
JAEA-Conf 2009-004, p.135 - 140, 2009/10
We have developed an original model based on the macroscopic and mean-field models to describe the global features of nuclear masses, called the KTUY (Koura-Tachibana-Uno-Yamada) nuclear mass model. The standard deviation of this prediction from known masses is 0.67 MeV, and below 0.4 MeV from some separation energies. The calculated separation energies shows a change of magicities from 
=20 (or 14) to 16, =28 to 32 (or 34), =50 to 58 etc.
-decay, -decay, proton emission and spontaneous fission ranging from light nuclei to superheavy nuclei including unknown ones, and estimated the dominant nuclear decay modes. A file of these nuclear data is presented. The total number of nuclei having more than 1 ns is estimated to be approximately ten thousands.
-delayed fission and neutron emission probabilities with the use of gross theory and KTUY mass formulaTachibana, Takahiro*; Koura, Hiroyuki; Chiba, Satoshi
JAEA-Conf 2009-004, p.129 - 134, 2009/10
Probabilities of the -delayed neutron emission are important information for decay heat calculation and, recently, the effect of the -delayed fission to the r-process nucleosynthesis is a quite interesting topic. We make an improvement of the calculation of the probabilities of -delayed fission and neutron emission for nuclei in the region far from the experimentally known nuclides. The probabilities of -delayed fission and neutron emission are estimated by using the gross theory of nuclear -decay. This theory includes the allowed (Fermi and Gamow-Teller) and first-forbidden transitions. In order to estimate the decay width 
and 
, we improve the calculation of nuclear level density formula by Kawano et. al. to take into account the effects of collective motion. We adopted the KTUY mass model for obtaining 
-values, neutron separation energies and fission barrier heights. The shell and the paring energies are also obtained by KTUY mass model for the calculation of the nuclear level density. We will apply these data to an r-process network calculation and briefly discuss the effect of nuclear fission to the r-process abundance in the presentation.
Chiba, Satoshi; Koura, Hiroyuki; Maruyama, Toshiki; Ota, Masahisa*; Tatsuda, Sayuki*; Wada, Takahiro*; Tachibana, Takahiro*; Sumiyoshi, Kosuke*; Otsuki, Kaori*; Kajino, Toshitaka*
AIP Conference Proceedings 1016, p.162 - 167, 2008/05
Effect of the -delayed fission in r-process abundance is investigated. The data base for the fission fragment mass distribution used in the r-process network calculation is constructed based on the 2-center shell model and Langevinequation. The -decay rates (no emissive, neutron emission and -delayed fission) are also newly calculated with the gross theory. The differences appeared in the final element abundance calculated with and without fission process are demonstrated and the mass region modified by the fission products is presented.
Ota, Masahisa*; Tatsuda, Sayuki*; Yamamoto, Kazuyuki*; Asano, Tomomasa*; Wada, Takahiro*; Hashizume, Kazuaki*; Sumiyoshi, Kosuke*; Otsuki, Kaori*; Kajino, Toshitaka*; Koura, Hiroyuki; et al.
Nuclear Physics A, 805(2), p.558 - 560, 2008/02
The data base for the fission fragment mass distribution used in the r-process network calculation is constructed. The differences appeared in the final element abundance calculated with and without fission process are demonstrated and the mass region modified by the fission products is presented.
Koura, Hiroyuki; Tachibana, Takahiro*
RIKEN Accelerator Progress Report, Vol.39, P. 30, 2006/05
no abstracts in English
Koura, Hiroyuki; Tachibana, Takahiro*
Nihon Butsuri Gakkai-Shi, 60(9), p.717 - 724, 2005/09
no abstracts in English
Koura, Hiroyuki; Tachibana, Takahiro*; Uno, Masahiro*; Yamada, Masami*
Progress of Theoretical Physics, 113(2), p.305 - 325, 2005/02
Times Cited Count：397 Percentile：99.16(Physics, Multidisciplinary)A nuclidic mass formula composed of a gross term, an even-odd term and a shell term is presented as a revised version of the mass formula constructed by the present authors and published in 2000. The gross term has almost the same functional form as in the previous formula, but the parameter values in it are somewhat different. The even-odd term is treated more carefully, and a considerable improvement is brought about. The shell term is exactly the same as the previous one; it was obtained using spherical single-particle potentials and by treating the deformed nucleus as a superposition of spherical nuclei. The new mass formula is applicable to nuclei with 
1 and 
1. The root-mean-square deviation from experimental masses is 0.658 MeV, which is less than that of the previous mass formula, 0.680 MeV.
Yoshida, Tadashi*; Okajima, Shigeaki; Sakurai, Takeshi; Nakajima, Ken; Yamane, Tsuyoshi; Katakura, Junichi; Tahara, Yoshihisa*; Zukeran, Atsushi*; Oyamatsu, Kazuhiro*; Osawa, Takaaki*; et al.
Journal of Nuclear Science and Technology, 39(Suppl.2), p.136 - 139, 2002/08
no abstracts in English
Katakura, Junichi; Yoshida, Tadashi*; Oyamatsu, Kazuhiro*; Tachibana, Takahiro*
JAERI 1343, 79 Pages, 2001/07
no abstracts in English
- and 
-ray spectra for JENDL FP decay data fileKatakura, Junichi; Yoshida, Tadashi*; Oyamatsu, Kazuhiro*; Tachibana, Takahiro*
Journal of Nuclear Science and Technology, 38(7), p.470 - 476, 2001/07
Times Cited Count：5 Percentile：38.97(Nuclear Science & Technology)no abstracts in English
-decay half-lives of new neutron-rich isotopes 
Tb and levels in DyAsai, Masato*; Ichikawa, Shinichi; Tsukada, Kazuaki; Sakama, Minoru*; Shibata, M.*; *; Osa, Akihiko; Nishinaka, Ichiro; Nagame, Yuichiro; Kawade, Kiyoshi*; et al.
Physical Review C, 59(6), p.3060 - 3065, 1999/06
Times Cited Count：33 Percentile：82.85(Physics, Nuclear)no abstracts in English
measurements of 
LaKojima, Yasuaki*; Asai, Masato*; Osa, Akihiko; Koizumi, Mitsuo; Sekine, Toshiaki; Shibata, M.*; *; Kawade, Kiyoshi*; Tachibana, Takahiro*
Journal of the Physical Society of Japan, 67(10), p.3405 - 3413, 1998/10
Times Cited Count：10 Percentile：58.6(Physics, Multidisciplinary)no abstracts in English
Tachibana, Takahiro*; *
JAERI-M 87-122, 56 Pages, 1987/08
no abstracts in English
Koura, Hiroyuki; Tachibana, Takahiro*; Chiba, Satoshi
no journal, ,
no abstracts in English
