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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.
Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.
Science, 364(6437), p.272 - 275, 2019/04
Times Cited Count：259 Percentile：99.73(Multidisciplinary Sciences)The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.
Wakasugi, Keiichiro; Yamaguchi, Masaaki; Koo, Shigeru*; Nagao, Fumiya; Kato, Tomoko; Suzuki, Yuji*; Ebashi, Takeshi; Umeki, Hiroyuki*; Niibori, Yuichi*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 16(1), p.15 - 33, 2017/03
This study provides a method of safety assessment for the geological disposal of HLW to evaluate the effects of uplift and erosion which are widespread phenomena identified on regional and global scales, and are more or less difficult to avoid in Japan. This method enables to deal with different uplift rate and erosion rate, and to evaluate repository depth, the time required for a repository to reach the weathered zone and surface of the ground, and the number of waste packages eroded as a function of time by using a landform evolution model. Based on trial analysis, the result shows that the maximum dose in the Base Case (uplift rate: 0.3 mm/y) is less than the targeted criterion suggested by the international organization even if the repository reaches the ground surface. Furthermore, the diversifying effect on timing the waste packages to reach to weathered zone due to heterogeneity on altitude of bottom of weathered zone reduces one order magnitude of result of the existed dose assessment. The new method is applicable to evaluate safety of geological disposal based on realistic phenomena of uplift and erosion and to quantify a safety margin and robustness of the disposal system.
Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Kitamura, Akira; Yoshikawa, Hideki; Oda, Chie; Ishidera, Takamitsu; et al.
JAEA-Research 2014-030, 457 Pages, 2015/03
JAEA-Research-2014-030.pdf:199.23MB
JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and post-closure performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, based on some examples of developing method of hydro-geological structure model, acquired knowledge are arranged using the tree diagram, and model uncertainty and its influence on the evaluation items were discussed. With regard to (2) study on scenario development, the developed approach for "defining conditions" has been reevaluated and improved from practical viewpoints. In addition, the uncertainty evaluation for the effect of use of cementitious material, as well as glass dissolution model, was conducted with analytical evaluation. With regard to (3) study on setting radionuclide migration parameters, based on survey of precedent procedures, multiple-approach for distribution coefficient of rocks was established, and the adequacy of the approach was confirmed though its application to sedimentary rock and granitic rock. Besides, an approach for solubility setting was developed including the procedure of selection of solubility limiting solid phase. The adequacy of the approach was confirmed though its application to key radionuclides.
Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Hayano, Akira; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.
JAEA-Research 2013-037, 455 Pages, 2013/12
JAEA-Research-2013-037.pdf:42.0MB
Following FY2011, JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, the tree diagram of methodology of groundwater travel time has been extended for crystalline rock, in addition, tree diagram for sedimentary rock newly has been organized. With regard to (2) study on scenario development, the existing approach has been improved in terms of a practical task, and applied and tested for near field focusing on the buffer. In addition, the uncertainty of some important processes and its impact on safety functions are discussed though analysis. With regard to (3) study on setting radionuclide migration parameters, the approaches for parameter setting have been developed for sorption for rocks and solubility, and applied and tested through parameter setting exercises for key radionuclides.
Tsuchida, Noriyuki*; Kawahata, Takuji*; Ishimaru, Eiichiro*; Takahashi, Akihiko*; Suzuki, Hiroshi; Shobu, Takahisa
ISIJ International, 53(7), p.1260 - 1267, 2013/07
Times Cited Count：24 Percentile：73.74(Metallurgy & Metallurgical Engineering)To investigate the tensile deformation behavior of a lean duplex stainless steel (S32101) from the viewpoints of plastic deformability among phases or grains, we performed static tensile tests, in situ neutron diffraction, and white X-ray diffraction experiments at room temperature. From the experimental results of synchrotron radiation white X-ray diffraction experiments, the hard phase of S32101 was changed from the ferrite phase to austenite one during tensile deformation. This led to a larger stress partitioning between the phases at the latter stage of deformation. From the experimental results of in situ neutron diffraction, it was found that the stress partitioning of the 
phase in the S32101 was the largest among the present results. Therefore, the larger work hardening rate of S32101 can be explained by the large stress partitioning of the phase, that between and 
phases and volume fraction.
Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Hayano, Akira; Mitsui, Seiichiro; Taniguchi, Naoki; Oda, Chie; Kitamura, Akira; Osawa, Hideaki; et al.
JAEA-Research 2012-032, 298 Pages, 2012/09
JAEA-Research-2012-032.pdf:33.68MB
JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and performance assessment in preliminary investigation phase. The topics and the conducted research are follows; (1) Study on selection of host rock: in terms of hydraulic properties, items for assessing rock property, and assessment methodology of groundwater travel time has been organized with interaction from site investigation. (2) Study on development of scenario: the existing approach has been embodied, in addition, the phenomenological understanding regarding dissolution of and nuclide release from vitrified waste, corrosion of the overpack, long-term performance of the buffer are summarized. (3) Study on setting nuclide migration parameters: the approach for parameter setting has been improved for sorption and diffusion coefficient of buffer/rock, and applied and tested for parameter setting of key radionuclides. (4) Study on ensuring quality of knowledge: framework for ensuring quality of knowledge has been studied and examined aimed at the likely disposal facility condition.
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.
and 
X-ray diffractions of corrosion products freshly formed on the surface of an iron-silicon alloySuzuki, Shigeru*; Matsubara, Eiichiro*; Komatsu, Takuya*; Okamoto, Yoshinori*; Kanie, Kiyoshi*; Muramatsu, Atsushi*; Konishi, Hiroyuki; Mizuki, Junichiro; Waseda, Yoshio*
Corrosion Science, 49(3), p.1081 - 1096, 2007/03
Times Cited Count：32 Percentile：80.42(Materials Science, Multidisciplinary) X-ray diffraction measurements of a small amount of samples extracted from wet corrosion products freshly formed on a pure iron and iron-2 mass% silicon surfaces have been conducted using synchrotron radiation. The results showed that -FeOOH was formed on the outer side of wet corrosion products formed on the pure iron by sodium chloride solution, while -FeOOH, -FeOOH, FeO, and green rusts were formed on the inner side. In comparison to the case of the pure iron, a significant formation of 
-FeOOH was observed in the iron-silicon alloy. Furthermore, in-situ diffraction measurements by a conventional X-ray source were conducted for analyzing corrosion products formed on the pure iron and iron-silicon alloy surfaces by cyclic exposure to wet and dry atmospheres. The results obtained by the diffraction and 
diffraction measurements on the corrosion products were consistent.
Higashitani, Atsushi*; Sugimoto, Tomoko*; Mori, Chihiro*; Suzuki, Yoko*; Saito, Rumiko*; Ichishi, Eiichiro*; Sakashita, Tetsuya; Hamada, Nobuyuki*; Wada, Seiichi*; Kakizaki, Takehiko; et al.
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 113, 2007/02
no abstracts in English
= 1 antiferromagnet observed by specific heat measurementsHagiwara, Masayuki*; Tsujii, Hiroyuki*; Rotundu, C. R.*; Andraka, B.*; Takano, Yasumasa*; Tateiwa, Naoyuki; Kobayashi, Tatsuo*; Suzuki, Takafumi*; Suga, Seiichiro*
Physical Review Letters, 96(14), p.147203_1 - 147203_4, 2006/04
Times Cited Count：18 Percentile：67.26(Physics, Multidisciplinary)Specific-heat experiments on single crystals of the = 1 quasi-one-dimensional bond-alternating antiferromagnet Ni(C
H
N
)(NO
)(ClO) (NTENP) have been performed in magnetic fields applied both parallel and perpendicular to the spin chains. We have found for the parallel field configuration that the magnetic specific heat (
) is proportional to temperature (
) above a critical field 
, at which the energy gap vanishes, in a temperature region above that of the long-range ordered state. The ratio = increases as the magnetic field approaches from above. The data are in good quantitative agreement with the prediction of the 
=1 conformal field theory in conjunction with the velocity of the excitations calculated by a numerical diagonalization, providing conclusive evidence for a Tomonaga-Luttinger liquid.
Kato, Tomoko; Suzuki, Yuji*; Makino, Hitoshi; Uchida, Masahiro; Naito, Morimasa; Wakasugi, Keiichiro*; Takahashi, Yoshiaki*
JNC TN1400 2005-024, 14 Pages, 2005/08
JNC-TN1400-2005-024.pdf:0.67MB
Biosphere assessment is positioned as part of an important factor in safety assessment to convert nuclide release rates into surface environment to measures of effect for human, such as radiation dose. In general, a lot of data are handled in the biosphere assessment, and they are based on the feature of specific site. Therefore, it is reasonable to screen parameters in order to manage the limited resource and develop the biosphere assessment effectively. JNC and NUMO established
Suzuki, Keiichi*; Nishiyama, Eiichiro*
JNC TJ7410 2005-002, 79 Pages, 2003/03
JNC-TJ7410-2005-002.PDF:19.85MB
no abstracts in English
Yamaguchi, Akihiro*; Iwadate, Mitsuo*; Suzuki, Eiichiro*; Yura, Kei; Kawakita, Shigetsune*; Umeyama, Hideaki*; Go, Michiko*
Nucleic Acids Research, 31(1), p.463 - 468, 2003/01
Times Cited Count：15 Percentile：25.22(Biochemistry & Molecular Biology)Enlarged FAMSBASE is a relational database of comparative protein structure models for the whole genome of 41 species, presented in the GTOP database. The models are calculated by FAMS, Full Automatic Modeling System. Enlarged FAMSBASE provides a wide range of query keys, such as name of ORF (open reading frame), ORF keywords, PDB ID, PDB heterogen atoms, and sequence similarity. Heterogen atoms in PDB include cofactors, ligands, and other factors that interact with proteins, and are a good starting point for analyzing interactions between proteins and other molecules. The data may also work as a template for drug design. The present number of ORFs with protein 3D models in FAMSBASE is 183,805, and the database includes an average of three models for each ORF. FAMSBASE is available at http://famsbase.bio.nagoya-u.ac.jp/famsbase/.
Umeki, Hiroyuki; Wakasugi, Keiichiro; ; Hasegawa, Shuichi*; Suzuki, Atsuyuki*
WSES/IEEE Kaigi, 0 Pages, 2001/00
None
Nagata, Hiroshi; Yamaura, Takayuki; Naka, Michihiro; Kawamata, Kazuo; Izumo, Hironobu; Hori, Naohiko; Nagao, Yoshiharu; Kusunoki, Tsuyoshi; Kaminaga, Masanori; Komori, Yoshihiro; et al.
no journal, ,
Conceptual design of the high-performance and low-cost next generation materials testing reactor which will be assumed to introduce to the nuclear power plant introduction country started from 2010 in the JAEA. Japanese atomic energy-related companies participate in this project, and this activity role as the environmental management and nuclear human resource development for the new research reactor designs. 10 MW thermal power by plate type fuel elements and swimming pool type was assumed as a design base. High safety, high cost performance, high reactor operation rate, high technology irradiation are targets of this conceptual design.
SR measurement of single-crystalline SmSIto, Takashi; Higemoto, Wataru; Suzuki, Hiroyuki*; Imura, Keiichiro*; Sato, Noriaki*
no journal, ,
no abstracts in English
Takir, D.*; Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; et al.
no journal, ,
JAXA spacecraft and sample return mission Hayabusa2 has arrived at the near-Earth asteroid 162173 Ryugu, which is classified a primitive carbonaceous object. Here we report recent results of near-infrared spectrometer (NIRS3) on the Hayabusa2 spacecraft. The observations provide direct measurements of the surface composition of Ryugu and context for the returned samples. NIRS3 has detected a weak and narrow absorption feature centered at 2.72 micrometer across entire observed surface. This absorption feature is attributed to the presence of OH-bearing minerals. The NIRS3 observations also revealed that Ryugu is the darkest object to be observed up-close by a visiting spacecraft. The intensity of the OH feature and low albedo are consistent with thermally-and/or shock-metamorphosed, and/or carbon-rich space-weathered primitive and hydrated carbonaceous chondrites.
Suzuki, Hiroyuki*; Kitayama, Ayami; Mitsui, Seiichiro; Taniguchi, Naoki
no journal, ,
The environmental conditions around carbon steel overpacks in geological disposal are expected to be diverse cases depending on geological environment of the repository and may also vary depending on changes in conditions after repository closure. In this study, with the aim of understanding corrosion behavior under such environmental conditions, immersion tests with different conditions were conducted in bentonite/silica sando mixture assuming a buffer material to be constructed around the overpack under a wide range of conditions, including temperature and water quality beyond the assumed range of conventional environmental conditions, and the effects on corrosion behavior were evaluated.
Taniguchi, Naoki; Kitayama, Ayami; Kawasaki, Manabu*; Nakayama, Masashi; Ono, Hirokazu; Mitsui, Seiichiro; Suzuki, Hiroyuki*
no journal, ,
no abstracts in English
