Dissolution and precipitation behaviors of zircon under the atmospheric environment

Kitagaki, Toru; Yoshida, Kenta*; Liu, P.*; Shobu, Takahisa

npj Materials Degradation (Internet), 6(1), p.13_1 - 13_8, 2022/02

https://doi.org/10.1038/s41529-021-00214-0

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.

Time-of-flight elastic and inelastic neutron scattering studies on the localized 4d electron layered perovskite LaMoO

Iida, Kazuki*; Kajimoto, Ryoichi; Mizuno, Yusuke*; Kamazawa, Kazuya*; Inamura, Yasuhiro; Hoshikawa, Akinori*; Yoshida, Yukihiko*; Matsukawa, Takeshi*; Ishigaki, Toru*; Kawamura, Yukihiko*; et al.

Journal of the Physical Society of Japan, 86(6), p.064803_1 - 064803_6, 2017/06

https://doi.org/10.7566/JPSJ.86.064803

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2013 - March 31, 2014)

Sato, Takeshi; Muto, Shigeo; Akiyama, Kiyomitsu; Aoki, Kazufumi; Okamoto, Akiko; Kawakami, Takeshi; Kume, Nobuhide; Nakanishi, Chika; Koie, Masahiro; Kawamata, Hiroyuki; et al.

JAEA-Review 2014-048, 69 Pages, 2015/02

JAEA-Review-2014-048.pdf:13.91MB

JAEA was assigned as a designated public institution under the Disaster Countermeasures Basic Act and under the Armed Attack Situations Response Act. Based on these Acts, the JAEA has the responsibility of providing technical support to the national government and/or local governments in case of disaster responses or response in the event of a military attack, etc. In order to fulfill the tasks, the JAEA has established the Emergency Action Plan and the Civil Protection Action Plan. In case of a nuclear emergency, NEAT dispatches specialists of JAEA, supplies the national government and local governments with emergency equipment and materials, and gives technical advice and information. In normal time, NEAT provides various exercises and training courses concerning nuclear disaster prevention to those personnel taking an active part in emergency response institutions of the national and local governments, police, fire fighters, self-defense forces, etc. in addition to the JAEA itself. The NEAT also researches nuclear disaster preparedness and response, and cooperates with international organizations. In the FY2013, the NEAT accomplished the following tasks: (1) Technical support activities as a designated public institution in cooperation with the national and local governments, etc. (2) Human resource development, exercise and training of nuclear emergency response personnel for the national and local governments, etc. (3) Researches on nuclear disaster preparedness and response, and sending useful information (4) International contributions to Asian countries on nuclear disaster preparedness and response in collaboration with the international organizations

Mechanism of synthesis of metallic oxide powder from aqueous metallic nitrate solution by microwave denitration method

Fukui, Kunihiro*; Igawa, Yusuke*; Arimitsu, Naoki*; Suzuki, Masahiro; Segawa, Tomoomi; Fujii, Kanichi*; Yamamoto, Tetsuya*; Yoshida, Hideto*

Chemical Engineering Journal, 211-212, p.1 - 8, 2012/11

https://doi.org/10.1016/j.cej.2012.09.032

The process for synthesizing metallic oxide powders by the microwave denitration method was investigated using hexahydrated nickel nitrate and trihydrated copper nitrate aqueous solutions, and the electrical field and the temperature distributions in the reactor were numerically simulated. Although CuO powder can be obtained from a trihydrated copper nitrate aqueous solution by the microwave denitration method, a hexahydrated nickel nitrate aqueous solution cannot be heated up to over 270 C by microwave irradiation. It was also found that the reaction routes for microwave heating are the same as those for conventional external heating. This finding indicates that the success of producing oxide particles by microwave denitration depends not only on the microwave absorptivity of the intermediate and the metallic oxide, but also on the temperature difference.

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.

Fuel-cell performance of multiply-crosslinked polymer electrolyte membranes prepared by two-step radiation technique

Yamaki, Tetsuya; Sawada, Shinichi; Asano, Masaharu; Maekawa, Yasunari; Yoshida, Masaru*; Gubler, L.*; Alkan Grsel, S.*; Scherer, G. G.*

ECS Transactions, 25(1), p.1439 - 1450, 2009/10

https://doi.org/10.1149/1.3210700

A multiply-crosslinked polymer electrolyte membrane was prepared by the radiation-induced co-grafting of styrene and a bis(vinyl phenyl)ethane (BVPE) crosslinker into a radiation-crosslinked polytetrafluoroethylene (cPTFE) film. We then investigated its hydrogen/oxygen fuel-cell performance at 60 and 80C in terms of the effect of radiation and chemical crosslinking. At 60C, all the membranes initially exhibited similar performance, but only the cPTFE-based membranes were durable at 80C, indicating the necessity of radiation crosslinking in the PTFE main chains. Importantly, cell performance of the multiply-crosslinked membrane was found high enough to reach that of a Nafion112 membrane. This is probably because the BVPE crosslinks in the graft component improved the membrane-electrode interface in addition to membrane durability. After severe OCV hold tests at 80 and 95C, the performance deteriorated, while no significant change was observed in ohmic resistivity. Accordingly, our membranes seemed so chemically stable that an influence on overall performance loss could be negligible.

The Development of Fe-nodules surrounding biological material mediated by microorganisms

Yoshida, Hidekazu; Yamamoto, Koshi*; Amano, Yuki; Katsuta, Nagayoshi*; Hayashi, Toru*; Naganuma, Takeshi

Environmental Geology, 55(6), p.1363 - 1374, 2008/09

https://doi.org/10.1007/s00254-007-1087-x

Takashikozo is a phenomenon of Quaternary sediments in Japan. They are cylindrical Fe-oxyhydroxide nodules that form as plaques round plant roots. Structural features suggest that after the roots have decayed, the central space where the roots were situated acts as a flow path for oxidized water. Analysis of microbial 16S rDNA extracted from the nodules identified iron-oxidizing bacteria encrusted round the roots where they are the likely initiators of nodule formation. Geological history and nanofossil evidence suggest that these Fe-nodules may have been buried at a depth of up to several tens of meters for a least 100000 years in reducing Quaternary sediments. Thus Fe-oxyhydroxide nodules with water and rock by microbial mediation can persist under reducing conditions. The phenomenon is significant as an analogue of post-closure conditions in radioactive waste repositories, since it could influence nuclide migration.

Preparation of radiation-grafted ion exchange membranes for application to fuel cells; New strategies emerging with recent developments

Yamaki, Tetsuya; Asano, Masaharu; Yoshida, Masaru*

Current Developments of Radiation-Induced Graft in Membranes, p.1 - 49, 2008/00

We reviewed many recent publications on radiation-grafted ion exchange membranes for fuel cells in terms of their preparation and characterization. At first, primary attention was paid to how to select the base polymer films and the monomers or monomer/crosslinker combinations in order to meet many fuel-cell requirements at the same time. Next, as a main subject, novel synthetic strategies emerging recently were highlighted: (1) a combination of radiation grafting with radiation crosslinking of the base polymer, giving a crosslinking structure of the fluorocarbon main chain, which is absent in the Nafion-like membranes; (2) the use of swift heavy ions as a radiation source to introduce the graft chains into only the very narrow cylindrical region along ion tracks, leading to the preparation of what is called "nano-structure controlled membranes." Finally, there remains an increasing necessity to pursue more basic research of the membrane regarding its structure and the behavior of the chemical species diffusing therein, i.e., protons, water, methanol, etc.

Preparation of ion-track membranes of poly(-phenylene terephthalamide); Control of pore shape by irradiation with different ion beams

Suzuki, Yasuyuki; Yamaki, Tetsuya; Koshikawa, Hiroshi; Asano, Masaharu; Voss, K.-O.*; Neumann, R.*; Yoshida, Masaru

Nuclear Instruments and Methods in Physics Research B, 260(2), p.693 - 695, 2007/07

https://doi.org/10.1016/j.nimb.2007.02.091

The preparation of ion-track membranes of thermally stable poly(p-phenylene terephthalamide) was performed by ion beam irradiation followed by chemical etching with a sodium hypochlorite solution. Cylindrical pores were observed in the membrane irradiated with Au and U ions at an energy of 11.1 MeV/n. In contrast, funnel shape pores appeared in the membrane irradiated with Kr, Ru and Xe ion at energies of 6.2, 3.6 and 3.5 MeV/n, respectively. The Au and U ion irradiation was found to exhibit more than four times larger sensitivity to the track etching under the same etching conditions. Consequently, the pore shape can be controlled by the masses and energies of the irradiated ions, in close relation to the etching sensitivity of the track.