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.

Adsorption of platinum-group metals and molybdenum onto aluminum ferrocyanide in spent fuel solution

Onishi, Takashi; Sekioka, Ken*; Suto, Mitsuo*; Tanaka, Kosuke; Koyama, Shinichi; Inaba, Yusuke*; Takahashi, Hideharu*; Harigai, Miki*; Takeshita, Kenji*

Energy Procedia, 131, p.151 - 156, 2017/12

https://doi.org/10.1016/j.egypro.2017.09.421

no abstracts in English

Orbital magnetic moment and coercivity of SiO-coated FePt nanoparticles studied by X-ray magnetic circular dichroism

Takahashi, Yukio*; Kadono, Toshiharu*; Yamamoto, Shimpei*; Singh, V. R.*; Verma, V.*; Ishigami, Keisuke*; Shibata, Goro*; Harano, Takayuki*; Takeda, Yukiharu; Okane, Tetsuo; et al.

Physical Review B, 90(2), p.024423_1 - 024423_5, 2014/07

AA2015-0417.pdf:0.45MB

https://doi.org/10.1103/PhysRevB.90.024423

ITER project; Status of procurement activities in domestic agency of Japan and application of HIP technology

Takatsu, Hideyuki; Enoeda, Mikio; Suzuki, Satoshi; Hirose, Takanori; Koizumi, Norikiyo; Takahashi, Koji

Proceedings of International Conference on Hot Isostatic Pressing (HIP '11), p.35 - 40, 2011/04

ITER is a mega-science fusion project, under an international collaboration of seven Members, to construct, operate, exploit and decommission a tokamak-type experimental reactor at Cadarache site with a mission to demonstrate the scientific and technological feasibility. The ITER Project started technical activities in 2007 and is now in a serious construction phase. Domestic Agencies of the seven member countries are in the process of manufacturing long lead-time components. Some of the ITER components apply HIP technology in manufacturing processes in view of a number of potential advantages. In this paper, examples and status of application of HIP technology by the Domestic Agency of Japan are overviewed.

Analysis of Th, U, Pu, and Am in radioactive metal waste using extraction chromatography

Shimada, Asako; Haraga, Tomoko; Hoshi, Akiko; Kameo, Yutaka; Nakashima, Mikio; Takahashi, Kuniaki

Journal of Radioanalytical and Nuclear Chemistry, 286(3), p.765 - 770, 2010/12

https://doi.org/10.1007/s10967-010-0750-y

Conceptual design of the SlimCS fusion DEMO reactor

Tobita, Kenji; Nishio, Satoshi*; Enoeda, Mikio; Nakamura, Hirofumi; Hayashi, Takumi; Asakura, Nobuyuki; Uto, Hiroyasu; Tanigawa, Hiroyasu; Nishitani, Takeo; Isono, Takaaki; et al.

JAEA-Research 2010-019, 194 Pages, 2010/08

JAEA-Research-2010-019-01.pdf:48.47MB
JAEA-Research-2010-019-02.pdf:19.4MB

This report describes the results of the conceptual design study of the SlimCS fusion DEMO reactor aiming at demonstrating fusion power production in a plant scale and allowing to assess the economic prospects of a fusion power plant. The design study has focused on a compact and low aspect ratio tokamak reactor concept with a reduced-sized central solenoid, which is novel compared with previous tokamak reactor concept such as SSTR (Steady State Tokamak Reactor). The reactor has the main parameters of a major radius of 5.5 m, aspect ratio of 2.6, elongation of 2.0, normalized beta of 4.3, fusion out put of 2.95 GW and average neutron wall load of 3 MW/m. This report covers various aspects of design study including systemic design, physics design, torus configuration, blanket, superconducting magnet, maintenance and building, which were carried out increase the engineering feasibility of the concept.

Analysis of the radioactivity concentrations in asphalt- or cement-solidified products generated from research facilities

Hoshi, Akiko; Kameo, Yutaka; Katayama, Atsushi; Sakai, Akihiro; Tsuji, Tomoyuki; Nakashima, Mikio; Kihara, Shinji; Takahashi, Kuniaki

JAEA-Data/Code 2009-023, 84 Pages, 2010/03

JAEA-Data-Code-2009-023.pdf:12.81MB

In order to establish the practical evaluation methods such as scaling factor method to determine the radioactivity concentrations of the important nuclides for safety assessment of disposal of radioactive wastes, we analyzed low-level radioactive liquid waste (56 samples), which is generated from various research facilities at Nuclear Science Research Institute from FY1998 to FY2007 and accumulated the radioactivity concentrations data (563 data) of the 17 important nuclides. We investigated the correlation of the radioactivity concentrations of the important nuclides with the "Key nuclides (Co or Cs)". In present paper, the radioactivity concentrations data of the 17 important nuclides and the results of the correlation of the radioactivity concentrations are summarized for the data to establish the practical evaluation methods to determine the radioactivity concentrations in asphalt-solidified or cement-solidified products.

Recent R&D activities of negative-ion-based ion source for JT-60SA

Ikeda, Yoshitaka; Hanada, Masaya; Kamada, Masaki; Kobayashi, Kaoru; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Inoue, Takashi; Honda, Atsushi; Kawai, Mikito; et al.

IEEE Transactions on Plasma Science, 36(4), p.1519 - 1529, 2008/08

https://doi.org/10.1109/TPS.2008.927382

The JT-60SA N-NBI system is required to inject 10 MW for 100 s at 500 keV. Three key issues should be solved for the JT-60SA N-NBI ion source. One is to improve the voltage holding capability. Recent R&D tests suggested that the accelerator with a large area of grids may need a high margin in the design of electric field and a long time for conditioning. The second issue is to reduce the grid power loading. It was found that some beamlets were strongly deflected due to beamlet-beamlet interaction and strike on the grounded grid. The grids are to be designed by taking account of beamlet-beamlet interaction in three-dimensional simulation. Third is to maintain the D- production for 100 s. A simple cooling structure is proposed for the active cooled plasma grid, where a key is the temperature gradient on the plasma grid for uniform D- production. The modified N-NBI ion source will start on JT-60SA in 2015.

Diagenesis and distribution of sterenes in Late Miocene to Pliocene marine siliceous rocks from Horonobe (Hokkaido, Japan)

Amo, Miki*; Suzuki, Noriyuki*; Shinoda, Toshio*; Ratnayake, N. P.*; Takahashi, Kazuharu

Organic Geochemistry, 38(7), p.1132 - 1145, 2007/07

https://doi.org/10.1016/j.orggeochem.2007.02.010

Late Miocene to Pliocene marine siliceous rocks in Horonobe, Hokkaido, Japan are rich in sterenes and steradienes. Diagenetic degradation and transformation of sterenes and steradienes in immature Horonobe marine siliceous rocks of Wakkanai and Koetoi Formations were studied using the borehole core samples from HDB-3 and HDB-4 drilled by Japan Atomic Energy Agency. The paleo-temperatures of marine siliceous rocks were estimated to be in the range from 30 to 60 C considering the silica mineral transformation from Opal-A to Opal-CT during diagenesis and the present day geothermal gradient in Horonobe region. Concentrations of steradienes and sterenes decrease quickly in the temperature range from 45 to 60 C. The significant increase of sterane concentration in the same temperature range shows that a part of steranes is derived from sterenes and steradienes. The sterane/sterene ratios of C, C, and C compounds change similarly with increasing maturity. The sterane/sterene ratio of Horonobe marine siliceous rocks can be a useful indicator of paleo-temperature. Either sterenes or steranes, the relative abundance of C, C, and C compounds is kept nearly similar all through the Horonobe boreholes, showing that their relative abundance is still applicable to the characterization of organic matter in immature sediments.

Extraction of uranium from simulated ore by the supercritical carbon dioxide fluid extraction method with nitric acid-TBP complex

Dung, L. T. K.*; Imai, Tomoki*; Tomioka, Osamu; Nakashima, Mikio; Takahashi, Kuniaki; Meguro, Yoshihiro

Analytical Sciences, 22(11), p.1425 - 1430, 2006/11

https://doi.org/10.2116/analsci.22.1425

Supercritical fluid extraction (SFE) method using supercritical CO fluid containing a complex of HNO-tri--butyl phosphate (TBP) as an extractant was applied to extract uranium from a several uranyl phosphate compounds and simulated uranium ores. Extraction method consisting of a static and a dynamic extraction processes was established and experimental condition such as pressure, temperature, and extraction time were optimized. It was found that uranium could be efficiently extracted from both of the uranyl phosphates and simulated ores by the SFE method and then it was demonstrated that SFE was useful as a pretreatment method for uranium analysis in ores.