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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：44 Percentile：97.1(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.
Ishihara, Keisuke; Yokota, Akira; Kanazawa, Shingo; Iketani, Shotaro; Sudo, Tomoyuki; Myodo, Masato; Irie, Hirobumi; Kato, Mitsugu; Iseda, Hirokatsu; Kishimoto, Katsumi; et al.
JAEA-Technology 2016-024, 108 Pages, 2016/12
JAEA-Technology-2016-024.pdf:29.74MB
Radioactive isotope, nuclear fuel material and radiation generators are utilized in research institutes, universities, hospitals, private enterprises, etc. As a result, various low-level radioactive wastes (hereinafter referred to as non-nuclear radioactive wastes) are produced. Disposal site for non-nuclear radioactive wastes have not been settled yet and those wastes are stored in storage facilities of each operator for a long period. The Advanced Volume Reduction Facilities (AVRF) are built to produce waste packages so that they satisfy requirements for shallow underground disposal. In the AVRF, low-level beta-gamma solid radioactive wastes produced in the Nuclear Science Research Institute are mainly treated. To produce waste packages meeting requirements for disposal safely and efficiently, it is necessary to cut large radioactive wastes into pieces of suitable size and segregate those depending on their types of material. This report summarizes activities of pretreatment to dispose of non-nuclear radioactive wastes in the AVRF.
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Al alloysSoda, Kazuo*; Harada, Shota*; Hayashi, Toshimitsu*; Kato, Masahiko*; Ishikawa, Fumihiro*; Yamada, Yu*; Fujimori, Shinichi; Saito, Yuji
Materials Transactions, 57(7), p.1040 - 1044, 2016/06
Times Cited Count：2 Percentile：12.16(Materials Science, Multidisciplinary)Sekimoto, Hitoshi*; Kawachi, Naoki; Honda, Shuzo*; Yamaguchi, Yoshie*; Kato, Shota*; Yoneyama, Kaori*; Fujimaki, Shu; Suzui, Nobuo; Ishii, Satomi; Watanabe, Satoshi; et al.
JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 124, 2008/03
no abstracts in English
Sekimoto, Hitoshi; Honda, Shuzo*; Kato, Shota*; Ochiai, Yukiko*; Yoneyama, Kaori*; Yoneyama, Koichi*; Takeuchi, Yasutomo*; Kawachi, Naoki; Fujimaki, Shu; Suzui, Nobuo; et al.
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 125, 2007/02
Jo, Akinori*; Kato, Shota*; Matsuura, Hirotaka*; Nagata, Kazumi*; Katakai, Akio; Tamada, Masao
no journal, ,
no abstracts in English
