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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.
Uwaba, Tomoyuki; Maeda, Seiichiro; Mizuno, Tomoyasu; Teague, M. C.*
Journal of Nuclear Materials, 429(1-3), p.149 - 158, 2012/10
Times Cited Count：4 Percentile：31.96(Materials Science, Multidisciplinary)Cladding strain caused by fuel/mechanical interaction (FCMI) was evaluated for mixed-oxide fuel elements subjected to 70-90% slow-ramp extended overpower transient tests in EBR-II. Calculated transient-induced cladding strains were correlated with cumulative damage fractions (CDFs) using cladding strength correlations. In a breached high-smeared density solid fuel element with low strength cladding, cladding thermal creep strain was significantly increased to approximately half the transient-induced cladding strain due to the tertiary creep when the CDF was close to the breach criterion (= 1.0). In low-smeared density annular fuel elements, FCMI load was significantly mitigated and resulted in little cladding strain. The CDFs of the annular fuel elements were lower than 0.01 at the end of the overpower transient, indicating a substantial margin to breach. A substantial margin to breach was also maintained in a high-smeared density fuel element with high strength cladding.
Fukuda, Akari*; Hagiwara, Hiroki; Ishimura, Toyoho*; Kozuka, Mariko*; Ioka, Seiichiro*; Amano, Yuki; Tsunogai, Urumu*; Suzuki, Yohei*; Mizuno, Takashi
Microbial Ecology, 60(1), p.214 - 225, 2010/05
Times Cited Count：29 Percentile：65.76(Ecology)To better understand the geochemical and microbiological relationships, we characterized granitic groundwater collected from a 1,148 to 1,169 -m deep borehole interval at the Mizunami Underground Research Laboratory site, Japan, in 2005 and 2008. Geochemical analyses of the groundwater samples indicated that major electron acceptors, such as NO
and SO
, were not abundant, while dissolved organic carbon (not including organic acids), CH and H
were moderately rich. The most common phylotypes were both related to 
spp., the cultivated members of which can utilize minor electron donors, such as aromatic and aliphatic hydrocarbons. Geomicrobiological results suggest that deep granitic groundwater has been stably colonized by spp. probably owing to the limitation of O, NO and organic acids.
Takahashi, Saburo; Kikuno, Hiroshi; Shiromo, Hideo; Kuba, Meiji; Abe, Tomoyuki; Takeda, Seiichiro
Proceedings of 16th Pacific Basin Nuclear Conference (PBNC-16) (CD-ROM), 6 Pages, 2008/10
Japan Atomic Energy Agency (JAEA) has been accumulating various experience and knowledge on development of MOX fuel technologies for more than 40 years since 1966. Plutonium Fuel Production Facility (PFPF) has introduced a fully automated and remote operation in 1988 as a pioneer in the world, based on the operational and technical experience obtained in the existing facilities. The PFPF has fabricated MOX fuel assemblies for a fast reactor "JOYO" and a fast breeder reactor "MONJU" so far. Through MOX fuel fabrication for JOYO and MONJU, many operational experiences such as a hold-up material problem have been gained. Based on the experiences, process equipments have been newly developed and a process technology has been improved. As the results, fully automated and remote fabrication technologies including easy contact maintenance of process equipments for FBR MOX fuel have been demonstrated in the PFPF on a large scale.
Iwatsuki, Teruki; Furue, Ryoji; Mie, Hideki; Ioka, Seiichiro; Mizuno, Takashi
Applied Geochemistry, 20(12), p.2283 - 2302, 2005/12
Times Cited Count：54 Percentile：71.59(Geochemistry & Geophysics)Hydrochemical conditions up to 1000m below ground level around the Mizunami Underground Research Laboratory were investigated to construct a baseline condition model descriving the undisturbed condition.
Mie, Hideki; Iwatsuki, Teruki; Furue, Ryoji; Mizuno, Takashi; Ioka, Seiichiro
JNC TN7400 2004-006, 64 Pages, 2004/10
JNC-TN7400-2004-006.pdf:9.26MBJNC-TN7400-2004-006(errata).pdf:0.08MB
This report describes the results of the investigation on the hydrochemical characteristic of groundwater in DH-15 borehole.
Yoshida, Zenko; Aoyagi, Hisao; ; Takeishi, Hideyo; Sasaki, Yuji; Uno, Seiichiro; Tachikawa, Enzo
Journal of Alloys and Compounds, 213-214, p.453 - 455, 1994/00
Times Cited Count：8 Percentile：54.8(Chemistry, Physical)no abstracts in English
Takada, Junichi; Koike, Tadao; Tsukamoto, Michio; Nishio, Gunji; Kitani, Susumu*; Uno, Seiichiro; ; Watanabe, Hironori; Hashimoto, Kazuichiro
JAERI-M 92-048, 332 Pages, 1992/03
no abstracts in English
Tsukamoto, Michio; Takada, Junichi; Koike, Tadao; Nishio, Gunji; Kitani, Susumu*; Uno, Seiichiro; ; Watanabe, Hironori; Hashimoto, Kazuichiro
JAERI-M 92-047, 384 Pages, 1992/03
no abstracts in English
Takada, Junichi; Koike, Tadao; Tsukamoto, Michio; Nishio, Gunji; Kitani, Susumu*; Uno, Seiichiro; ; Watanabe, Hironori; Hashimoto, Kazuichiro
JAERI-M 91-145, 195 Pages, 1991/09
no abstracts in English
Hashimoto, Kazuichiro; Soda, Kunihisa; Uno, Seiichiro
Proc. of the Int. Topical Meeting on Safety of Thermal Reactors, p.740 - 745, 1991/00
no abstracts in English
Hashimoto, Kazuichiro; Soda, Kunihisa; Uno, Seiichiro; ; *
Severe Accidents in Nuclear Power Plants,Vol. 2, p.77 - 86, 1988/00
no abstracts in English
Iwatsuki, Teruki; Mie, Hideki; Mizuno, Takashi; Amano, Yuki; Ioka, Seiichiro
no journal, ,
no abstracts in English
Ioka, Seiichiro; Iwatsuki, Teruki; Mizuno, Takashi; Kato, Osamu*; Imakita, Tsuyoshi*
no journal, ,
no abstracts in English
Maeda, Seiichiro; Mizuno, Tomoyasu; Aoyama, Takafumi; Kitamura, Ryoichi; Takeuchi, Norihiko; Abe, Tomoyuki
no journal, ,
To confirm thermal performance of FBR-MOX fuels containing minor actinides such as americium, the irradiation experiment was performed with low-density MOX fuels containing americium at a high linear power in the fast experimental reactor "Joyo". The post-irradiation-experiment is successively proceeding at hot cell facilities. An overall plan and an outline of the irradiation program are presented in this report.
