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Journal Articles

Fundamental experiments of jet impingement and fragmentation simulating the fuel relocation in the core disruptive accident of sodium-cooled fast reactors

Imaizumi, Yuya; Kamiyama, Kenji; Matsuba, Kenichi; Isozaki, Mikio; Suzuki, Toru; Emura, Yuki

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 5 Pages, 2017/04

In order to simulate the typical accident conditions of the fuel relocation phase in SFRs, the molten alloy of low melting point was discharged into a shallow water pool. The distance between the nozzle exit and the bottom plate was set to a value which was indicated to be insufficient to fragment. As the experimental result, the melt jet reached the bottom plate, and dispersed in all directions along the plate, together with the progress of fragmentation. In addition, the melt temperature on the bottom plate decreased rapidly along the radius direction. These results suggest that the fragmentation which would accompany this rapid cooling would be enhanced by the plate. This enhancement would be caused by the extension of the melt-water interface when the melt was dispersed forcibly by the plate. The solidified debris remained after the discharge showed remarkable fragmentation which was assumed to be caused by the formations of small vapor bubbles in the interface.

Journal Articles

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.

JAEA Reports

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$$^{2}$$. 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.

JAEA Reports

Preparation of reference material for solidified products made from radioactive miscellaneous wastes by melting treatment; Reference material for solidified product containing $$alpha$$-ray emitting nuclides (Joint research)

Ishimori, Kenichiro; Oki, Keiichi; Takaizumi, Hirohide; Kameo, Yutaka; Oki, Yoshiyuki*; Nakashima, Mikio

JAEA-Technology 2007-065, 20 Pages, 2008/01

JAEA-Technology-2007-065.pdf:1.4MB

In order to prepare a reference material which is used for radiochemical analysis of solidified products made from non-metallic miscellaneous low level radioactive solid wastes by melting in Nuclear Science Research Institute, Japan Atomic Energy Agency, the preparation method of the reference material was investigated. Under the optimum melting conditions obtained in this report, the reference material containing $$^{237}$$Np, $$^{241}$$Am and $$^{244}$$Cm as $$alpha$$-ray emitting nuclides was successfully prepared. From radiochemical analysis of the reference material, the radioactive concentration of respective nuclides was determined to be 0.188$$pm$$0.001 Bq/g for $$^{237}$$Np, 0.368$$pm$$0.004 Bq/g for $$^{241}$$Am, 0.402$$pm$$0.010 Bq/g for $$^{244}$$Cm.

Journal Articles

Engineering design of the ITER invessel neutron monitor using micro-fission chambers

Nishitani, Takeo; Yamauchi, Michinori; Izumi, Mikio*; Hayakawa, Atsuro*; Ebisawa, Katsuyuki*; Kondoh, Takashi; Kusama, Yoshinori

Fusion Engineering and Design, 82(5-14), p.1192 - 1197, 2007/10

 Times Cited Count:5 Percentile:36.73(Nuclear Science & Technology)

no abstracts in English

Journal Articles

SlimCS; Compact low aspect ratio DEMO reactor with reduced-size central solenoid

Tobita, Kenji; Nishio, Satoshi; Sato, Masayasu; Sakurai, Shinji; Hayashi, Takao; Shibama, Yusuke; Isono, Takaaki; Enoeda, Mikio; Nakamura, Hirofumi; Sato, Satoshi; et al.

Nuclear Fusion, 47(8), p.892 - 899, 2007/08

 Times Cited Count:59 Percentile:86.84(Physics, Fluids & Plasmas)

The concept for a compact DEMO reactor named "SlimCS" is presented. Distinctive features of the concept is low aspect ratio ($$A$$ = 2.6) and use of a reduced-size center solenoid (CS) which has a function of plasma shaping rather than poloidal flux supply. The reduced-size CS enables us to introduce a thin toroidal field (TF) coil system which contributes to reducing the weight and construction cost of the reactor. SlimCS is as compact as advanced commercial reactor designs such as ARIES-RS and produces 1 GWe in spite of moderate requirements for plasma parameters. Merits of low-$$A$$, i.e. vertical stability for high elongation and high beta limit are responsible for such reasonable physics requirements.

Journal Articles

Innovative alpha-radioactivity monitor for clearance level inspection based on ionized air transportation technology, 1; Comparison with mass spectral analysis using uranium-attached samples

Aoyama, Yoshio; Miyamoto, Yasuaki; Yamaguchi, Hiromi; Sano, Akira*; Naito, Susumu*; Sumida, Akio*; Izumi, Mikio*; Maekawa, Tatsuyuki*; Sato, Mitsuyoshi*; Nambu, Kenichi*; et al.

Proceedings of 15th International Conference on Nuclear Engineering (ICONE-15) (CD-ROM), 6 Pages, 2007/04

no abstracts in English

Journal Articles

Ion current prediction model considering columnar recombination in alpha radioactivity measurement using ionized air transportation

Naito, Susumu*; Hirata, Yosuke*; Izumi, Mikio*; Sano, Akira*; Miyamoto, Yasuaki; Aoyama, Yoshio; Yamaguchi, Hiromi

Journal of Nuclear Science and Technology, 44(2), p.121 - 128, 2007/02

 Times Cited Count:1 Percentile:11.16(Nuclear Science & Technology)

A reinforced ion current prediction model in the alpha radioactivity measurement using ionized air transportation was presented. Although our previous model explained a qualitative trend of the measured ion current values, their absolute values were considerably overestimated. In order to explain them quantitatively, the model was reinforced in consideration of columnar recombination. It was found that our new model explains the considerable ion loss in the initial stage of ion diffusion and narrows the gap between the predicted and measured ion current values. This model also indicated a prospective suppression of ion loss due to columnar recombination by spraying a high-speed air flow on the contaminated surface. This suppression was experimentally investigated and confirmed. In conclusion, the theoretical relationship between alpha radioactivity and ion current was clarified quantitatively in laminar flow and turbulent pipe flow.

Journal Articles

Particle modeling of transport of $$alpha$$-ray generated ion clusters in air

Tong, L.*; Nambu, Kenichi*; Hirata, Yosuke*; Izumi, Mikio*; Miyamoto, Yasuaki; Yamaguchi, Hiromi

Japanese Journal of Applied Physics, Part 1, 45(10B), p.8217 - 8220, 2006/10

 Times Cited Count:0 Percentile:0.00(Physics, Applied)

A particle model is developed using the test-particle Monte Carlo method to study the transport properties of alpha-ray generated ion clusters in a flow of air. The simulated transport properties provide a theoretical basis for designing the alpha radioactivity measurement system. An accurate ion-molecule collision model is proposed to simulate the collisions between ion and air molecule. The recombination between positive and negative ions is simulated using Nanu and Denpoh method [J. Phys. Soc. Jpn. 67(1998) 1288]. The calculations are performed from low gas pressures of 0.001 and 0.01 atm to high gas pressures of 0.1 and 1 atm in a circular pipe. The simulation presents such a steady state ion transport that the generation of ions reaches a quasi-equilibrium with the loss of ions, absorbed by a measuring sensor and lost on the pipe wall.

Journal Articles

Concept of compact low aspect ratio Demo reactor, SlimCS

Tobita, Kenji; Nishio, Satoshi; Sato, Masayasu; Sakurai, Shinji; Hayashi, Takao; Shibama, Yusuke; Isono, Takaaki; Enoeda, Mikio; Nakamura, Hirofumi; Sato, Satoshi; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2006/10

no abstracts in English

Journal Articles

Neutron powder diffraction study on the crystal and magnetic structures of BiCoO$$_3$$

Belik, A. A.*; Iikubo, Satoshi; Kodama, Katsuaki; Igawa, Naoki; Shamoto, Shinichi; Niitaka, Seiji*; Azuma, Masaki*; Shimakawa, Yuichi*; Takano, Mikio*; Izumi, Fujio*; et al.

Chemistry of Materials, 18(3), p.798 - 803, 2006/02

 Times Cited Count:282 Percentile:98.60(Chemistry, Physical)

The crystal and magnetic structures of polycrystalline BiCoO$$_3$$ have been determined by the Rietveldmethod from neutron diffraction data measured at temperatures from 5 to 520 K. BiCoO$$_3$$ (space groupP4mm; Z=1; a=3.72937(7) ${AA}$ and c=4.72382(15) ${AA}$ at room temperature; tetragonality c/a=1.267) is isotypic with BaTiO$$_3$$ and PbTiO$$_3$$ in the whole temperature range. BiCoO$$_3$$ is an insulator with a Neeltemperature of 470 K. A possible model for antiferromagnetic order is proposed with a propagationvector of k=(1/2, 1/2, 0). In this model, magnetic moments of Co$$^{3+}$$ ions are parallel to the c directionand align antiferromagnetically in the ab plane. The antiferromagnetic ab layers stack ferromagneticallyalong the c axis, forming a C-type antiferromagnetic structure. Refined magnetic moments at 5 and 300K are 3.24(2)$$mu$$$$_B$$ and 2.93(2)$$mu$$$$_B$$, respectively. The structure refinements revealed no deviation fromstoichiometry in BiCoO$$_3$$. BiCoO$$_3$$ decomposed in air above 720 K to give Co$$_3$$O$$_4$$ and sillenite-like Bi$$_{25}$$CoO$$_{39}$$.

Journal Articles

Design study of fusion DEMO plant at JAERI

Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Sato, Masayasu; Isono, Takaaki; Sakurai, Shinji; Nakamura, Hirofumi; Sato, Satoshi; Suzuki, Satoshi; Ando, Masami; et al.

Fusion Engineering and Design, 81(8-14), p.1151 - 1158, 2006/02

 Times Cited Count:124 Percentile:98.97(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Radon concentration dependence of alpha radioactivity measurement using ionized air transportation

Naito, Susumu*; Sano, Akira*; Izumi, Mikio*; Noda, Etsuo*; Hayashi, Kazuo*; Sato, Mitsuyoshi*; Suto, Osamu; Miyamoto, Yasuaki; Kondo, Shinichi*; Iinuma, Koichi*; et al.

Nuclear Science Symposium Conference Record, 2005 IEEE, Vol.1, p.495 - 499, 2005/10

An alpha radioactivity monitor (alpha-clearance monitor) is being developed to measure alpha radioactivity of uranium contaminated waste with large and complex surfaces. It uses an alpha radioactivity measurement method by collecting the air ionized by alpha particles using an air stream and by measuring its ion current. One of the major problems of the alpha-clearance monitor is the background ion current mainly by radon in atmosphere ($$sim$$700 fA), which is much larger than ion current of an alpha particle (several fA). It strongly influences on the detection limit of alpha radioactivity. In order to improve the detection limit, we developed a method to monitor the radon concentration inside the monitor without the additional radon detector. In addition, the influencing factors on the detection limit: ion mobility and ion recombination coefficient were measured and evaluated on various environmental conditions (temperature, humidity and aerosol density).

JAEA Reports

Design of micro-fission chambers for ITER low power operations

Nishitani, Takeo; Yamauchi, Michinori*; Izumi, Mikio*; Kusama, Yoshinori

JAERI-Tech 2005-047, 34 Pages, 2005/09

JAERI-Tech-2005-047.pdf:6.75MB

no abstracts in English

Journal Articles

Fusion reactor technology; Challenge to future energy

Seki, Masahiro; Hishinuma, Akimichi; Kurihara, Kenichi; Akiba, Masato; Abe, Tetsuya; Ishitsuka, Etsuo; Imai, Tsuyoshi; Enoeda, Mikio; Ohira, Shigeru; Okumura, Yoshikazu; et al.

Kaku Yugoro Kogaku Gairon; Mirai Enerugi Eno Chosen, 246 Pages, 2001/09

no abstracts in English

Journal Articles

Layered pebble bed concept for ITER breeding blanket

Takatsu, Hideyuki; Mori, Seiji*; Yoshida, Hiroshi; Hashimoto, T.*; Kurasawa, Toshimasa; Koizumi, Koichi; Enoeda, Mikio; Sato, Satoshi; Kuroda, Toshimasa*; ; et al.

Fusion Technology 1992, p.1504 - 1508, 1993/00

no abstracts in English

Oral presentation

Simplification of procedure for radiochemical analysis of solidified products, 5; Separation method for $$^{14}$$C

Ishimori, Kenichiro; Oki, Keiichi; Kameo, Yutaka; Takaizumi, Hirohide; Nakashima, Mikio; Oki, Yoshiyuki*; Isogai, Keisuke*

no journal, , 

no abstracts in English

Oral presentation

Studies on relocation behavior of molten core materials in the core disruptive accident of sodium-cooled fast reactors, 1; Overall plan

Kamiyama, Kenji; Matsuba, Kenichi; Isozaki, Mikio; Imaizumi, Yuya; Suzuki, Toru; Emura, Yuki

no journal, , 

no abstracts in English

Oral presentation

Alpha radioactivity measurement based on ionized air transportation technology

Aoyama, Yoshio; Miyamoto, Yasuaki; Yamaguchi, Hiromi; Naito, Susumu*; Sano, Akira*; Izumi, Mikio*; Sumida, Akio*; Maekawa, Tatsuyuki*; Sato, Mitsuyoshi*; Nambu, Kenichi*; et al.

no journal, , 

Radioactive waste contaminated by Uranium has been accumulated in front-end facilities of the nuclear fuel cycle. The purpose of the present project is to develop the practical and highly efficient measurement system, which solves the above-mentioned requirements based on the innovative concept of indirect alpha radioactivity measurement using ionized air stream transportation. The ionized air by alpha particles near the waste is peeled and transported into the ion sensor by controlling air stream in the measurement system. In order to give the actual solution for this indirect measurement concept, we have to clarify various basic physics concerning with radiation ionizing process in the air, ion reaction process in the air, ion transportation process by the turbulent air flow, and measurement process in the ion sensor. For this purpose, we have to develop various analytical simulation technologies for predicting ion behavior as well as direct measurement technologies of ion spatial distribution. The final target of the project is to establish the practical and verified clearance confirmation technology based on the above-mentioned physical and technological knowledge.

Oral presentation

Simplification of procedure for radiochemical analysis of solidified products, 8; A Highly sensitive non-destructive measurement by multi-parameter coincidence $$gamma$$-ray spectrometry

Haraga, Tomoko; Kameo, Yutaka; Kimura, Atsushi; Koizumi, Mitsuo; Toh, Yosuke; Nakashima, Mikio

no journal, , 

no abstracts in English

24 (Records 1-20 displayed on this page)