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Journal Articles

Mesospheric ionization during substorm growth phase

Murase, Kiyoka*; Kataoka, Ryuho*; Nishiyama, Takanori*; Nishimura, Koji*; Hashimoto, Taishi*; Tanaka, Yoshimasa*; Kadokura, Akira*; Tomikawa, Yoshihiro*; Tsutsumi, Masaki*; Ogawa, Yasunobu*; et al.

Journal of Space Weather and Space Climate (Internet), 12, p.18_1 - 18_16, 2022/06

 Times Cited Count:0 Percentile:0.01(Astronomy & Astrophysics)

We identified two energetic electron precipitation (EEP) events during the growth phase of moderate substorms and estimated the mesospheric ionization rate for an EEP event for which the most comprehensive dataset from ground-based and space-born instruments was available. The mesospheric ionization signature reached below 70 km altitude and continued for ~15 min until the substorm onset, as observed by the PANSY radar and imaging riometer at Syowa Station in the Antarctic region. We also used energetic electron flux observed by the Arase and POES 15 satellites as the input for the air-shower simulation code PHITS to quantitatively estimate the mesospheric ionization rate. Combining the cutting-edge observations and simulations, we shed new light on the space weather impact of the EEP events during geomagnetically quiet times, which is important to understand the possible link between the space environment and climate.

Journal Articles

Atmospheric resuspension of insoluble radioactive cesium bearing particles found in the difficult-to-return area in Fukushima

Tang, P.*; Kita, Kazuyuki*; Igarashi, Yasuhito*; Satou, Yukihiko; Hatanaka, Kotaro*; Adachi, Koji*; Kinase, Takeshi*; Ninomiya, Kazuhiko*; Shinohara, Atsushi*

Progress in Earth and Planetary Science (Internet), 9(1), p.17_1 - 17_15, 2022/03

 Times Cited Count:0 Percentile:0.01(Geosciences, Multidisciplinary)

Journal Articles

Distinct variation of electronic states due to annealing in $$T'$$-type La$$_{1.8}$$Eu$$_{0.2}$$CuO$$_{4}$$ and Nd$$_{2}$$CuO$$_{4}$$

Asano, Shun*; Ishii, Kenji*; Matsumura, Daiju; Tsuji, Takuya; Kudo, Kota*; Taniguchi, Takanori*; Saito, Shin*; Sunohara, Toshiki*; Kawamata, Takayuki*; Koike, Yoji*; et al.

Physical Review B, 104(21), p.214504_1 - 214504_7, 2021/12

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Journal Articles

High oxide-ion conductivity in Si-deficient La$$_{9.565}$$(Si$$_{5.826}$$[]$$_{0.174}$$)O$$_{26}$$ apatite without interstitial oxygens due to the overbonded channel oxygens

Fujii, Kotaro*; Yashima, Masatomo*; Hibino, Keisuke*; Shiraiwa, Masahiro*; Fukuda, Koichiro*; Nakayama, Susumu*; Ishizawa, Nobuo*; Hanashima, Takayasu*; Ohara, Takashi

Journal of Materials Chemistry A, 6(23), p.10835 - 10846, 2018/06

 Times Cited Count:19 Percentile:65.98(Chemistry, Physical)

Journal Articles

Mn$$_{2}$$VAl Heusler alloy thin films; Appearance of antiferromagnetism and exchange bias in a layered structure with Fe

Tsuchiya, Tomoki*; Kobayashi, Ryota*; Kubota, Takahide*; Saito, Kotaro*; Ono, Kanta*; Ohara, Takashi; Nakao, Akiko*; Takanashi, Koki*

Journal of Physics D; Applied Physics, 51(6), p.065001_1 - 065001_7, 2018/02

 Times Cited Count:5 Percentile:33.2(Physics, Applied)

Journal Articles

Examination of analytical method of rare earth elements in used nuclear fuel

Ozawa, Mayumi; Fukaya, Hiroyuki; Sato, Makoto; Kamohara, Keiko*; Suyama, Kenya; Tonoike, Kotaro; Oki, Keiichi; Umeda, Miki

Proceedings of 53rd Annual Meeting of Hot Laboratories and Remote Handling Working Group (HOTLAB 2016) (Internet), 9 Pages, 2016/11

JAEA Reports

Preliminary conceptual design of the secondary sodium circuit-eliminated JSFR (Japan Sodium Fast Reactor) adopting a supercritical CO$$_{2}$$ turbine system, 2; Turbine system and plant size

Kisohara, Naoyuki; Sakamoto, Yoshihiko; Kotake, Shoji*

JAEA-Research 2014-016, 60 Pages, 2014/09


JAEA has performed a design study of an S-CO$$_{2}$$ gas turbine system applied to the JSFR. In this study, the S-CO$$_{2}$$ cycle turbine system was directly connected to the primary sodium system of the JSFR to eliminate the secondary sodium circuit, aiming for further economical improvement. This report describes the system configuration, heat/mass balance, and main components of the S-CO$$_{2}$$ turbine system, based on the JSFR specifications. The layout of components and piping in the reactor and turbine buildings were examined and the dimensions of the buildings were estimated. The study has revealed that the reactor and turbine buildings could be reduced by 7% and 40%, respectively, in comparison with those in the existing JSFR design with the secondary sodium circuit employing the steam turbine. The cycle thermal was also calculated as 41.9-42.3%, which is nearly the same as that of the JSFR with the water/steam system.

JAEA Reports

Preliminary conceptual design of the secondary sodium circuit-eliminated JSFR (Japan Sodium Fast Reactor) adopting a supercritical CO$$_{2}$$ turbine system, 1; Sodium/CO$$_{2}$$ heat exchanger

Kisohara, Naoyuki; Sakamoto, Yoshihiko; Kotake, Shoji*

JAEA-Research 2014-015, 33 Pages, 2014/09


JAEA has performed a design study of an S-CO$$_{2}$$ gas turbine system applied to the JSFR. In this study, the S-CO$$_{2}$$ cycle turbine system was directly connected to the primary sodium system of the JSFR to eliminate the secondary sodium circuit, aiming for further economical improvement. The Na/CO$$_{2}$$ heat exchanger is one of the key components, and this report describes its structure and the safety in case of CO$$_{2}$$ leak. A Printed Circuit Heat Exchanger (PCHE) is employed to the heat exchanger. A SiC/SiC ceramic composite material is used for the PCHE to prevent crack growth and to reduce thermal stress. The Na/CO$$_{2}$$ heat exchanger has been designed in such a way that a number of small heat transfer modules are combined in the vessel in consideration of manufacture and repair. CO$$_{2}$$ leak events in the heat exchanger have been also evaluated, and it revealed that no significant effect has arisen on the core or the primary sodium boundary.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation report for the 2011 fiscal year

Nakayama, Masashi; Amano, Kenji; Tokiwa, Tetsuya; Yamamoto, Yoichi; Oyama, Takuya; Amano, Yuki; Murakami, Hiroaki; Inagaki, Daisuke; Tsusaka, Kimikazu; Kondo, Keiji; et al.

JAEA-Review 2012-035, 63 Pages, 2012/09


The Horonobe Underground Research Laboratory Project is planned to extend over a period 20 years. The investigations will be conducted in three phases, namely "Phase 1: Surface-based investigations", "Phase 2: Construction Phase" (investigations during construction of the underground facilities) and "Phase 3: Operation phase"(research in the underground facilities). This report summarizes the results of the investigations for the 2011 fiscal year (2011/2012). The investigations, which are composed of "Geoscientific research" and "R&D on geological disposal technology", were carried out according to "Horonobe Underground Research Laboratory Project Investigation Program for the 2011 Fiscal year". The results of these investigations, along with the results which were obtained in other departments of Japan Atomic Energy Agency (JAEA), are properly offered to the implementations and the safety regulations. For the sake of this, JAEA has proceeded with the project in collaboration with experts from domestic and overseas research organisations.

JAEA Reports

Horonobe Underground Research Laboratory Project; Research and development plan (H22-H26)

Iwatsuki, Teruki; Sato, Haruo; Nohara, Tsuyoshi; Tanai, Kenji; Sugita, Yutaka; Amano, Kenji; Yabuuchi, Satoshi; Oyama, Takuya; Amano, Yuki; Yokota, Hideharu; et al.

JAEA-Research 2011-009, 73 Pages, 2011/06


The research and development plan in Horonobe Underground Research Laboratory are summarized according to the 2nd Midterm Plan till 2014 fiscal year of JAEA. In this midterm, galleries and the infrastructures for the research and development up to the depth of 350 m are constructed by Private Financial Initiative (PFI). Additionally Phase 3: Operation phase at the galleries begins in parallel to Phase 2: Construction phase. In these phases various research and development including collaboration with other institutes are conducted at the galleries. Generallic applicable techniques on the subject of the investigation of geological environment, facility construction in deep underground and the reliability of geological deposal are developed during the phase. The feasibility and reliance of various technologies concerning geological disposal is demonstrated by widely opening the outcome to the public in the society.

Journal Articles

Binomial distribution function for intuitive understanding of fluence dependence of non-amorphized ion-track area

Ishikawa, Norito; Ohara, Kota; Ota, Yasuyuki*; Michikami, Osamu*

Nuclear Instruments and Methods in Physics Research B, 268(19), p.3273 - 3276, 2010/10

 Times Cited Count:10 Percentile:59.04(Instruments & Instrumentation)

In this experiment, CeO$$_{2}$$ thin films are irradiated with 200 MeV Au to investigate the damage created by electronic energy deposition. The damage is studied by Raman spectroscopy.

Journal Articles

Anneal temperature effect on crystallite size and electric conductivity of LiMn$$_{2}$$O$$_{4}$$

Basar, K.*; Xianglian*; Siagian, S.*; Ohara, Kota*; Sakuma, Takashi*; Takahashi, Haruyuki*; Abe, Osami*; Igawa, Naoki; Ishii, Yoshinobu*

Indonesian Journal of Physics, 20(1), p.9 - 11, 2009/01

Nanosized LiMn$$_{2}$$O$$_{4}$$ has been successfully prepared by solid state reaction of LiOH and MnO$$_{2}$$. Neutron scattering experiments at room temperature and conductivity measurement have been performed on the samples. Anneal temperature effect on the crystallite size and electric conductivity of LiMn$$_{2}$$O$$_{4}$$ is analyzed. The average crystallite size is obtained from the full width at half maximum (FWHM) of Bragg lines using Scherrer equation. The average crystallite size increases with the increase of anneal temperature. Activation energy and conductivity prefactor increase with anneal temperature.

Journal Articles

Effect of Pb-Pb correlation in diffuse scattering of powder PbF$$_{2}$$

Xianglian*; Basar, K.*; Honda, Hiroyuki*; Siagian, S.*; Ohara, Kota*; Sakuma, Takashi*; Takahashi, Haruyuki*; Igawa, Naoki; Ishii, Yoshinobu*

Solid State Ionics, 179(21-26), p.776 - 779, 2008/09

 Times Cited Count:2 Percentile:12.47(Chemistry, Physical)

Diffuse X-ray and neutron scattering from powder PbF$$_{2}$$ are measured at 15 and 294K. Those oscillatory profile of diffuse scattering is explained by including the correlation effects among thermal displacements of atoms. The contribution of correlated thermal vibration of Pb-Pb atoms located at far-off distance to the oscillatory profile of diffuse scattering intensities is first confirmed.

JAEA Reports

Studies of super-critical CO$$_{2}$$ gas turbine power generation fast reactor(Contract research, Translated document)

Kisohara, Naoyuki; Kotake, Shoji; Sakamoto, Yoshihiko

JAEA-Review 2008-040, 67 Pages, 2008/08


(1) Preliminary design of an SFR that adopts a super-critical CO$$_{2}$$ turbine has been made. This SFR system eliminates secondary sodium circuits. The power generation efficiency of the SFR is 42%. Compared to a SFR that adopts a steam cycle with secondary sodium circuits, the reactor building volume of the SC-CO$$_{2}$$ SFR is reduced by 20%. (2) A super-critical CO$$_{2}$$ cycle test loop was fabricated. The high efficiency of a compressor is confirmed near the super-critical region. The temperature efficiencies of PCHE recuperators are 98-99% (hot leg). No flow instability is observed in the loop operation. (3) Na/CO$$_{2}$$ Reaction tests were executed. Continuous reaction occurs more than 570-580$$^{circ}$$C. Reaction products are Na$$_{2}$$CO$$_{3}$$ and CO. The reaction heat is 50-75kJ/Na-mol. (4) Safety calculation was done for 1 DEG tube failure in Na/CO$$_{2}$$ heat exchanger. The maximum pressure in the primary circuit is below the allowed level. The void reactivity of the reactor core also has no affect. The reaction product brought no sodium flow blockage in fuel assemblies. (5) After an exposure of 600$$^{circ}$$C-5000 hours in super-critical CO$$_{2}$$ environment, the corrosion of 12Cr steel and 316FR were 170g/m$$^{2}$$ and 5g/m$$^{2}$$, respectively. 316 FR shows a good corrosion proof property.

Journal Articles

Study of structural change in CeO$$_{2}$$ irradiated with high-energy ions by means of X-ray diffraction measurement

Ishikawa, Norito; Chimi, Yasuhiro; Michikami, Osamu*; Ota, Yasuyuki*; Ohara, Kota; Lang, M.*; Neumann, R.*

Nuclear Instruments and Methods in Physics Research B, 266(12-13), p.3033 - 3036, 2008/06

 Times Cited Count:38 Percentile:91.94(Instruments & Instrumentation)

Cerium dioxide films are irradiated with high-energy heavy ions with the energy range of 150 MeV to 2.7 GeV, and X-ray diffraction profile is examined. As a result, the data can be explained by creation of nanometer-size ion track with disordered lattice structure, and the ion track is oxygen deficient.

Journal Articles

Microbeam system for heavy ions from cyclotron to irradiate living cells

Yokota, Wataru; Ohara, Yoshihiro; Arakawa, Kazuo

Proceedings of 36th ICFA Advanced Beam Dynamics Workshop (NANOBEAM 2005) (CD-ROM), 6 Pages, 2005/10

no abstracts in English

Oral presentation

Surface oxidation and tribological properties of a hydrogenated DLC exposed to a simulated low earth orbit space environment

Tagawa, Masahito*; Asada, Hidetoshi*; Yokota, Kumiko*; Ohara, Hisanori*; Nakahigashi, Takahiro*; Teraoka, Yuden; Martin, J. M.*; Belin, M.*

no journal, , 

Effect of space environment on a hydrogenated diamond-like carbon (DLC), which is a candidate of next generation space-approved solid lubricant, has been studied. No significant changes in friction coefficient and surface oxidation states were detected with energetic atomic oxygen fluence of 5$$times$$10$$^{18}$$ atoms/cm$$^{2}$$.

Oral presentation

Effect of hyperthermal atomic oxygen exposures on hydrogenated diamond-like carbon films

Yokota, Kumiko*; Asada, Hidetoshi*; Tagawa, Masahito*; Ohara, Hisanori*; Nakahigashi, Takahiro*; Yoshigoe, Akitaka; Teraoka, Yuden; Martin, J. M.*; Belin, M.*

no journal, , 

Hydrogenated diamond-like carbon (DLC) is expected as a lubricant for space uses because of its ultra low friction charactor in vacuum. Thus, DLC films were exposed to atomic oxygens which were generated by a laser detonation method simulating a low orbit space environment. The DLC surfaces were analysed and the results are reported in this talk. The hydrogenated amorphous DLC was fabricated by a RF-CVD method on Si substrates. Relative collision energy of space planes against atomic oxygens can be simulated with the space environment experimental apparatus. The DLC films exposed to atomic oxygens were analysed by an SR-PES method etc. The SR-PES was performed at the surface chemical reaction analysis station installed in the BL23SU of SPring-8. It was suggested that some volatile oxides were formed and desorbed from the DLC surface when DLC surface was irradiated by atomic oxygens with an incident energy of 4.2 eV and fluence of 5$$times$$10$$^{18}$$atoms/cm$$^{2}$$.

Oral presentation

Diffuse scattering of PbF$$_{2}$$

Xianglian*; Basar, K.*; Sainer, S.*; Ohara, Kota*; Sakuma, Takashi*; Takahashi, Haruyuki*; Igawa, Naoki; Ishii, Yoshinobu

no journal, , 

no abstracts in English

Oral presentation

Development research of a reliable steam generator with solid cupper

Aizawa, Kosuke; Kisohara, Naoyuki; Kotake, Shoji; Sherwood, D. V.*

no journal, , 

no abstracts in English

39 (Records 1-20 displayed on this page)