Thermally altered subsurface material of asteroid (162173) Ryugu

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

https://doi.org/10.1038/s41550-020-01271-2

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.

Monitoring of airborne C discharge at RI facilities; A Comparison of collection and oxidation methods

Ueno, Yumi; Koarashi, Jun; Iwai, Yasunori; Sato, Junya; Takahashi, Teruhiko; Sawahata, Katsunori; Sekita, Tsutomu; Kobayashi, Makoto; Tsunoda, Masahiko; Kikuchi, Masamitsu

Hoken Butsuri, 49(1), p.39 - 44, 2014/03

http://doi.org/10.5453/jhps.49.39

http://doi.org/10.5453/jhps.49.2

The Japan Atomic Energy Agency has conducted a monthly monitoring of airborne C discharge at the forth research building (RI facility) of the Tokai Research and Development Center. In the current monitoring, C, which exists in various chemical forms in airborne effluent, is converted into CO with CuO catalyst and then collected using monoethanolamine (MEA) as CO absorbent. However, this collection method has some issues on safety management because the CuO catalyst requires a high heating temperature (600C) to ensure a high oxidation efficiency and the MEA is specified as a poisonous and deleterious substance. To establish a safer, manageable and reliable method for monitoring airborne C discharge, we examined collection methods that use different CO absorbents (MEA and Carbo-Sorb E) and oxidation catalysts (CuO, Pt/Alumina and Pd/ZrO). The results showed 100% CO collection efficiency of MEA during a 30-day sampling period under the condition tested. In contrast, Carbo-Sorb E was found to be unsuitable for the monthly-long CO collection because of its high volatile nature. Among the oxidation catalysts, the Pd/ZrO showed the highest oxidation efficiency for CH at a lower temperature.

Characterization of 316L(N)-IG SS joint produced by hot isostatic pressing technique

Nakano, Junichi; Miwa, Yukio; Tsukada, Takashi; Kikuchi, Masahiko; Kita, Satoshi; Nemoto, Yoshiyuki; Tsuji, Hirokazu; Jitsukawa, Shiro

Journal of Nuclear Materials, 307-311(Part2), p.1568 - 1572, 2002/12

https://doi.org/10.1016/S0022-3115(02)00965-0

Type 316LN stainless steel of the international thermonuclear experimental reactor (ITER) Grade (316LN-IG SS) is being considered for the first wall/ blanket component. Hot isostatic pressing (HIP) technique is expected for the fabrication of module. To evaluate the integrity and susceptibility to stress corrosion cracking (SCC) of HIPed 316LN-IG SS, tensile tests in vacuum and slow strain rate tests (SSRT) in high temperature water were performed. Specimen with the HIPed joint shows no deterioration of the tensile strength and susceptibility to SCC in oxygenated water. Thermally sensitized specimen with the HIPed joint was low susceptible to SCC in creviced environment. It is concluded that the strength at joint location is as high as that at the base alloy and the joint interface appears integrity.

Development of analytical method and study about microstructure of oxide films on stainless steel

Nemoto, Yoshiyuki; Miwa, Yukio; Kikuchi, Masahiko; Kaji, Yoshiyuki; Tsukada, Takashi; Tsuji, Hirokazu

Journal of Nuclear Science and Technology, 39(9), p.996 - 1001, 2002/09

https://doi.org/10.3327/jnst.39.996

Surface morphology of oxidized stainless steel was evaluated using atomic force microscope (AFM) and scanning electron microscope (FE-SEM). Cross-sectional morphology of oxide layer on the specimens was evaluated using FE-SEM after fabrication. Focused ion beam (FIB) technique was applied to fabricate thin film samples of oxide films, which were used for microstructure observation by transmission electron microscope (FE-TEM), and microscopic chemical analysis by energy dispersed X-ray spectrometer (EDS). These preparations and observations were successful, and microstructure and chemical composition of oxide films were evaluated on nanometer scale. Effects of silicon (Si) doping and dissolved oxygen (DO) content in water for oxide layer formation are discussed.

Development of analytical method for microstructure observation of oxide film on stainless steel

Nemoto, Yoshiyuki; Miwa, Yukio; Tsukada, Takashi; Kikuchi, Masahiko; Tsuji, Hirokazu

JAERI-Tech 2001-079, 25 Pages, 2001/12

JAERI-Tech-2001-079.pdf:6.76MB

Development and research about analytical method for the study of oxide film on austenitic stainless steel had been conducted from the point of view for basic study of IASCC (Irradiation Assisted Stress Corrosion Cracking). Nickel plating and copper plating had been compared as the oxide film protection while the fabrication for cross sectional observation. And thin film specimens for microstructural observation were fabricated using FIB (Focused Ion Beam) technique. Microstructure of oxide film on stainless steel had been observed with FE-TEM (Field Emission gun - Transmission Electron Microscope), and the chemical composition was analyzed with EDS (Energy dispersed X-ray Spectrometer). The oxide film had been formed in high pressure (8MPa) and high temperature (288) water, contains saturated oxygen. The thickness of oxide film was about 1m as maximum. Micro grains of Fe oxide with 100nm in diameter were formed in the oxide film. On the boundary with alloy, there was about 10nm thickness of passive film formed with Cr oxide.

Alloying Effects on Young's Modulus and Vickers Hardness of Zirconium, and Construction of Characteristics Diagrams for Alloy Design

Shibutani, Hideo*; Morinaga, Masahiko*; *; Matsushita, Kenichi*; Kikuchi, Keiichi

Nihon Genshiryoku Gakkai-Shi, 40(6), p.501 - 508, 1998/06

https://doi.org/10.3327/jaesj.40.501

None

Nodular corrosion of zirconium alloys and XPS analysis of surface oxide layer

Shibutani, Hideo*; Morinaga, Masahiko*; Kikuchi, Keiichi

Nihon Kinzoku Gakkai-Shi, 62(6), p.534 - 541, 1998/00

None

Investigation about C monitoring in RI facilities

Ueno, Yumi; Takahashi, Teruhiko; Sawahata, Katsunori; Kikuchi, Masamitsu; Tsunoda, Masahiko

no journal, , 

no abstracts in English