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Journal Articles

Thermophysical properties of dense molten Al$$_{2}$$O$$_{3}$$ determined by aerodynamic levitation

Sun, Y.*; Takatani, Tomoya*; Muta, Hiroaki*; Fujieda, Shun*; Kondo, Toshiki; Kikuchi, Shin; Kargl, F.*; Oishi, Yuji*

International Journal of Thermophysics, 45(1), p.11_1 - 11_19, 2024/01

no abstracts in English

Journal Articles

Thermophysical properties of molten (Fe$$_{2}$$O$$_{3}$$)$$_{0.95}$$-(SiO$$_{2}$$)$$_{0.05}$$ measured by aerodynamic levitation

Kondo, Toshiki; Toda, Taro*; Takeuchi, Junichi*; Kikuchi, Shin; Kargl, F.*; Muta, Hiroaki*; Oishi, Yuji*

High Temperatures-High Pressures, 52(3-4), p.307 - 321, 2023/06

 Times Cited Count:0 Percentile:0.02(Thermodynamics)

In order to establish an evaluation method/numerical simulation for nuclear reactor safety under severe accidental conditions, it is necessary to obtain the physical properties, especially fluidity of the relevant molten materials at very high temperatures. In this study, thermophysical properties such as density and viscosity were obtained for (Fe$$_{2}$$O$$_{3}$$)$$_{0.95}$$-(SiO$$_{2}$$)$$_{0.05}$$, which is a representative composition in the early stage of severe accident. (Fe$$_{2}$$O$$_{3}$$)$$_{0.95}$$-(SiO$$_{2}$$)$$_{0.05}$$ is produced by the contact between the molten oxide of steel, which is the main component of the reactor, and SiO$$_{2}$$, which is the main component of concrete. As a result, the physical properties of the (Fe$$_{2}$$O$$_{3}$$)$$_{0.95}$$-(SiO$$_{2}$$)$$_{0.05}$$ mixture were almost the same as those of Fe$$_{2}$$O$$_{3}$$ obtained in previous studies, and it could be concluded that a small amount of SiO$$_{2}$$ (about 5 mol.%) did not significantly affect the fluidity of Fe$$_{2}$$O$$_{3}$$.

Journal Articles

Thermophysical properties of molten FeO$$_{1.5}$$, (FeO$$_{1.5}$$)$$_{0.86}$$-(ZrO$$_{2}$$)$$_{0.14}$$ and (FeO$$_{1.5}$$)$$_{0.86}$$-(UO$$_{2}$$)$$_{0.14}$$

Kondo, Toshiki; Toda, Taro*; Takeuchi, Junichi*; Kargl, F.*; Kikuchi, Shin; Muta, Hiroaki*; Oishi, Yuji*

Journal of Nuclear Science and Technology, 59(9), p.1139 - 1148, 2022/09

 Times Cited Count:1 Percentile:33.72(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Surface nanostructures on Nb-doped SrTiO$$_{3}$$ irradiated with swift heavy ions at grazing incidence

Ishikawa, Norito; Fujimura, Yuki; Kondo, Keietsu; Szabo, G. L.*; Wilhelm, R. A.*; Ogawa, Hiroaki; Taguchi, Tomitsugu*

Nanotechnology, 33(23), p.235303_1 - 235303_10, 2022/06

 Times Cited Count:2 Percentile:51.2(Nanoscience & Nanotechnology)

A single crystal of SrTiO$$_{3}$$ doped with niobium (Nb-STO) was irradiated with 200 MeV Au ions at grazing incidence. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to study the relation between irradiation-induced change of surface topography and corresponding material property changes. As expected, multiple hillocks as high as 5-6 nm are imaged by AFM observation. It is also found that the region in between the adjacent hillocks is slightly elevated rather than depressed. Line-like contrasts along the ion paths are found in both AFM phase images and SEM images, indicating the formation of continuous ion tracks in addition to multiple hillocks. Cross-sectional transmission electron microscopy (TEM) observation shows that the ion tracks in the near-surface region are found to be relatively large, whereas buried ion tracks in the deeper region are relatively small. The results suggest that recrystallization plays an important role in the formation of small ion tracks in the deep region, whereas formation of large ion tracks in the near-surface region is likely due to the absence of recrystallization.

Journal Articles

High temperature gas-cooled reactors

Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950$$^{circ}$$C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.

Journal Articles

A Model intercomparison of atmospheric $$^{137}$$Cs concentrations from the Fukushima Daiichi Nuclear Power Plant accident, phase III; Simulation with an identical source term and meteorological field at 1-km resolution

Sato, Yosuke*; Sekiyama, Tsuyoshi*; Fang, S.*; Kajino, Mizuo*; Qu$'e$rel, A.*; Qu$'e$lo, D.*; Kondo, Hiroaki*; Terada, Hiroaki; Kadowaki, Masanao; Takigawa, Masayuki*; et al.

Atmospheric Environment; X (Internet), 7, p.100086_1 - 100086_12, 2020/10

The third model intercomparison project for investigating the atmospheric behavior of $$^{137}$$Cs emitted during the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident (FDNPP-MIP) was conducted. A finer horizontal grid spacing (1 km) was used than in the previous FDNPP-MIP. Nine of the models used in the previous FDNPP-MIP were also used, and all models used identical source terms and meteorological fields. Our analyses indicated that most of the observed high atmospheric $$^{137}$$Cs concentrations were well simulated, and the good performance of some models improved the performance of the multi-model ensemble. The analyses also confirmed that the use of a finer grid resolution resulted in the meteorological field near FDNPP being better reproduced. The good representation of the wind field resulted in the reasonable simulation of the narrow distribution of high deposition amount to the northwest of FDNPP and the reduction of the overestimation over the area to the south of FDNPP. In contrast, the performance of the models in simulating plumes observed over the Nakadori area, the northern part of Gunma, and the Tokyo metropolitan area was slightly worse.

Journal Articles

Intercomparison of numerical atmospheric dispersion prediction models for emergency response to emissions of radionuclides with limited source information in the Fukushima Dai-ichi Nuclear Power Plant accident

Iwasaki, Toshiki*; Sekiyama, Tsuyoshi*; Nakajima, Teruyuki*; Watanabe, Akira*; Suzuki, Yasushi*; Kondo, Hiroaki*; Morino, Yu*; Terada, Hiroaki; Nagai, Haruyasu; Takigawa, Masayuki*; et al.

Atmospheric Environment, 214, p.116830_1 - 116830_11, 2019/10

 Times Cited Count:6 Percentile:27(Environmental Sciences)

The utilization of numerical atmospheric dispersion prediction (NDP) models for accidental discharge of radioactive substances was recommended by a working group of the Meteorological Society of Japan. This paper is to validate the recommendation through NDP model intercomparison in the accidental release from the Fukushima Dai-ichi Nuclear Power Plant in 2011. Emission intensity is assumed to be constant during the whole forecast period for the worst-case scenario unless time sequence of emission is available. We expect to utilize forecasts of surface air contaminations for preventions of inhalations of radioactive substances, and column-integrated amounts for mitigation of radiation exposure associated with wet deposition. Although NDP forecasts have ensemble spread, they commonly figure out relative risk in space and time. They are of great benefit to disseminating effective warnings to public without failure. The multi-model ensemble technique may be effective to improve the reliability.

Journal Articles

Model intercomparison of atmospheric $$^{137}$$Cs from the Fukushima Daiichi Nuclear Power Plant accident; Simulations based on identical input data

Sato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki; Nagai, Haruyasu; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qu$'e$lo, D.*; et al.

Journal of Geophysical Research; Atmospheres, 123(20), p.11748 - 11765, 2018/10

 Times Cited Count:39 Percentile:85.11(Meteorology & Atmospheric Sciences)

A model intercomparison of the atmospheric dispersion of $$^{137}$$Cs emitted following the Fukushima Daiichi Nuclear Power Plant accident was conducted by 12 models to understand the behavior of $$^{137}$$Cs in the atmosphere. The same meteorological data, horizontal grid resolution, and an emission inventory were applied to all the models to focus on the model variability originating from the processes included in each model. The multi-model ensemble captured 40% of the observed $$^{137}$$Cs events, and the figure-of-merit in space for the total deposition of $$^{137}$$Cs exceeded 80. Our analyses indicated that the meteorological data were most critical for reproducing the $$^{137}$$Cs events. The results also revealed that the differences among the models were originated from the deposition and diffusion processes when the meteorological field was simulated well. However, the models with strong diffusion tended to overestimate the $$^{137}$$Cs concentrations.

Journal Articles

Comprehensive seismic evaluation of HTTR against the 2011 off the Pacific coast of Tohoku Earthquake

Ono, Masato; Iigaki, Kazuhiko; Sawahata, Hiroaki; Shimazaki, Yosuke; Shimizu, Atsushi; Inoi, Hiroyuki; Kondo, Toshinari; Kojima, Keidai; Takada, Shoji; Sawa, Kazuhiro

Journal of Nuclear Engineering and Radiation Science, 4(2), p.020906_1 - 020906_8, 2018/04

On March 11th, 2011, the 2011 off the Pacific coast of Tohoku Earthquake of magnitude 9.0 occurred. When the great earthquake occurred, the High Temperature Engineering Test Reactor (HTTR) had been stopped under the periodic inspection and maintenance of equipment and instruments. A comprehensive integrity evaluation was carried out for the HTTR facility because the maximum seismic acceleration observed at the HTTR exceeded the maximum value of design basis earthquake. The concept of comprehensive integrity evaluation is divided into two parts. One is the "visual inspection of equipment and instruments". The other is the "seismic response analysis" for the building structure, equipment and instruments using the observed earthquake. All equipment and instruments related to operation were inspected in the basic inspection. The integrity of the facilities was confirmed by comparing the inspection results or the numerical results with their evaluation criteria. As the results of inspection of equipment and instruments associated with the seismic response analysis, it was judged that there was no problem for operation of the reactor, because there was no damage and performance deterioration. The integrity of HTTR was also supported by the several operations without reactor power in cold conditions of HTTR in 2011, 2013 and 2015. Additionally, the integrity of control rod guide blocks was also confirmed visually when three control rod guide blocks and six replaceable reflector blocks were taken out from reactor core in order to change neutron startup sources in 2015.

Journal Articles

Establishment of integrity evaluation method for Reserved Shutdown System of High-Temperature engineering Test Reactor (HTTR)

Hamamoto, Shimpei; Kawamoto, Taiki; Kondo, Makoto; Sawahata, Hiroaki; Takada, Shoji; Shinozaki, Masayuki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 15(2), p.66 - 69, 2016/06

High Temperature engineering Test Reactor (HTTR) has the reactivity control system which is accompanied with the Reserved Shutdown System (RSS). The RSS consists of B$$_{4}$$C/C pellets, guide tube, electric plug, motor which contains brake and reducer, and so on. In accidents when the control rods cannot be inserted, an electric plug is pulled out by motor and the B$$_{4}$$C/C pellets fall into the core by gravity. It was revealed that the motor in the RSS drive mechanism did not work as the result of pre-start up checks as described followings: (1) The oil which was separated from a grease of motor reducer flowed down from gap of oil seal, (2) the separated oil penetrated into the brake, (3) the penetrated oil was mixed with abrasion powder released from brake disk, finally, (4) the adhesive mixture blocked the rotation of the motor. A new evaluation method was proposed to detect a sign of the motor sticking. Through the overhaul inspection of all RSS drive mechanisms of HTTR, it was revealed that the proposed method was effective to evaluate the integrity of the RSS drive mechanism.

Journal Articles

Baseline design of a proton linac for BNCT at OIST

Kondo, Yasuhiro; Hasegawa, Kazuo; Higashi, Yasuo*; Sugawara, Hirotaka*; Yoshioka, Masakazu*; Kumada, Hiroaki*; Matsumoto, Hiroshi*; Naito, Fujio*; Kurokawa, Shinichi*

Proceedings of 7th International Particle Accelerator Conference (IPAC '16) (Internet), p.906 - 909, 2016/06

An accelerator based boron neutron capture therapy (BNCT) facility is being planned at Okinawa institute of science and technology (OIST). The proton accelerator consists of a radio frequency quadrupole (RFQ) linac and a drift tube linac (DTL). The required beam power is 60 kW. The present beam energy and current are 10 MeV and 30 mA, respectively. The pulse length is 3.3 ms and the repetition rate is 60 Hz, therefore, the duty factor is 20%. In this paper, present design of this compact, medium current, high duty proton linac is presented.

Journal Articles

Ion acceleration via "nonlinear vacuum heating" by the laser pulse obliquely incident on a thin foil target

Yogo, Akifumi*; Bulanov, S. V.; Mori, Michiaki; Ogura, Koichi; Esirkepov, T. Z.; Pirozhkov, A. S.; Kanasaki, Masato*; Sakaki, Hironao; Fukuda, Yuji; Bolton, P.; et al.

Plasma Physics and Controlled Fusion, 58(2), p.025003_1 - 025003_7, 2016/02

 Times Cited Count:8 Percentile:42.32(Physics, Fluids & Plasmas)

Journal Articles

Cumulative history recorded in the depth distribution of radiocesium in sediments deposited on a sandbar

Tanaka, Kazuya; Kondo, Hiroaki*; Sakaguchi, Aya*; Takahashi, Yoshio*

Journal of Environmental Radioactivity, 150, p.213 - 219, 2015/12

 Times Cited Count:4 Percentile:12.67(Environmental Sciences)

We collected sediments deposited on a sandbar from the surface to 20 cm in depth in the Abukuma River to clarify the history of radiocesium derived from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. We analyzed the $$^{137}$$Cs concentration in the sediments from size-fractioned samples as well as bulk samples. The results of this study demonstrated that sediment layers deposited on a sandbar retained the cumulative history of the fluvial transport of radiocesium after the FDNPP accident.

Journal Articles

Development of a proton accelerator for OIST BNCT

Kondo, Yasuhiro; Hasegawa, Kazuo; Higashi, Yasuo*; Kumada, Hiroaki*; Kurokawa, Shinichi*; Matsumoto, Hiroshi*; Naito, Fujio*; Yoshioka, Masakazu*

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.948 - 950, 2015/09

An accelerator based boron neutron capture therapy (BNCT) facility is being planned at Okinawa institute of science and technology (OIST). The proton accelerator consists of a radio frequency quadrupole (RFQ) linac and a drift tube linac (DTL). The reqired beam power is 60 kW. The present beam energy and current are 10 MeV and 30 mA, respectively. The pulse length is 3.3 ms and the repetition rate is 60 Hz, therefore, the duty factor is 20%. In this paper, present designof this compact, midium current, high duty proton linac is presented.

Journal Articles

Development of the maintenance technologies for the future high-temperature gas cooled reactor (HTGR) using operating experiences acquired in high-temperature engineering test reactor (HTTR)

Shimazaki, Yosuke; Homma, Fumitaka; Sawahata, Hiroaki; Furusawa, Takayuki; Kondo, Masaaki

Journal of Nuclear Science and Technology, 51(11-12), p.1413 - 1426, 2014/11

 Times Cited Count:3 Percentile:31.13(Nuclear Science & Technology)

Journal Articles

Partial photoneutron cross sections for $$^{207,208}$$Pb

Kondo, Takeo*; Utsunomiya, Hiroaki*; Goriely, S.*; Iwamoto, Chihiro*; Akimune, Hidetoshi*; Yamagata, Tamio*; Toyokawa, Hiroyuki*; Harada, Hideo; Kitatani, Fumito; Lui, Y.-W.*; et al.

Nuclear Data Sheets, 119, p.310 - 313, 2014/05

 Times Cited Count:2 Percentile:19.31(Physics, Nuclear)

Journal Articles

Report of the Special Symposium on the Transport and Diffusion of Contaminants from the Fukushima Dai-ichi Nuclear Power Plant; Present status and future directions

Kondo, Hiroaki*; Yamada, Tetsuji*; Chino, Masamichi; Iwasaki, Toshiki*; Katata, Genki; Maki, Takashi*; Saito, Kazuo*; Terada, Hiroaki; Tsuruta, Haruo*

Tenki, 60(9), p.723 - 729, 2013/09

AA2013-0745.pdf:0.51MB

no abstracts in English

Journal Articles

Photoneutron cross sections for Mo isotopes; A Step toward a unified understanding of($$gamma$$,n) and (n,$$gamma$$)reactions

Utsunomiya, Hiroaki*; Goriely, S.*; Kondo, Takeo*; Iwamoto, Chihiro*; Akimune, Hidetoshi*; Yamagata, Tamio*; Toyokawa, Hiroyuki*; Harada, Hideo; Kitatani, Fumito; Lui, Y.-W.*; et al.

Physical Review C, 88(1), p.015805_1 - 015805_6, 2013/07

 Times Cited Count:72 Percentile:96.67(Physics, Nuclear)

Journal Articles

Development of small specimen test techniques for the IFMIF test cell

Wakai, Eiichi; Kim, B. J.; Nozawa, Takashi; Kikuchi, Takayuki; Hirano, Michiko*; Kimura, Akihiko*; Kasada, Ryuta*; Yokomine, Takehiko*; Yoshida, Takahide*; Nogami, Shuhei*; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 6 Pages, 2013/03

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

JAEA-Review-2012-035.pdf:12.23MB

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.

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