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Journal Articles

Radioactivity and radionuclides in deciduous teeth formed before the Fukushima-Daiichi Nuclear Power Plant accident

Takahashi, Atsushi*; Chiba, Mirei*; Tanahara, Akira*; Aida, Jun*; Shimizu, Yoshinaka*; Suzuki, Toshihiko*; Murakami, Shinobu*; Koarai, Kazuma; Ono, Takumi*; Oka, Toshitaka; et al.

Scientific Reports (Internet), 11(1), p.10355_1 - 10355_11, 2021/05

 Times Cited Count:5 Percentile:42.99(Multidisciplinary Sciences)

Journal Articles

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

 Times Cited Count:30 Percentile:96.87(Astronomy & Astrophysics)

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 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$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.

Journal Articles

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

 Times Cited Count:14 Percentile:74.77(Physics, Multidisciplinary)

The structure of a neutron-rich $$^{25}$$F nucleus is investigated by a quasifree ($$p,2p$$) knockout reaction. The sum of spectroscopic factors of $$pi 0d_{5/2}$$ orbital is found to be 1.0 $$pm$$ 0.3. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus, and the core consists of $$sim$$35% $$^{24}$$O$$_{rm g.s.}$$, and $$sim$$65% excited $$^{24}$$O. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus. The result may infer that the addition of the $$0d_{5/2}$$ proton considerably changes the neutron structure in $$^{25}$$F from that in $$^{24}$$O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

Journal Articles

Ultra-high temperature tensile properties of ODS steel claddings under severe accident conditions

Yano, Yasuhide; Tanno, Takashi; Oka, Hiroshi; Otsuka, Satoshi; Inoue, Toshihiko; Kato, Shoichi; Furukawa, Tomohiro; Uwaba, Tomoyuki; Kaito, Takeji; Ukai, Shigeharu*; et al.

Journal of Nuclear Materials, 487, p.229 - 237, 2017/04

 Times Cited Count:32 Percentile:96.87(Materials Science, Multidisciplinary)

Ultra-high temperature ring tensile tests were carried out to investigate the tensile behavior of oxide dispersion strengthened (ODS) steel claddings and wrapper materials under severe accident conditions; temperatures ranged from room temperature to 1400$$^{circ}$$C which is near the melting point of core materials. The experimental results showed that tensile strength of 9Cr-ODS steel claddings was highest in the core materials at the ultra-high temperatures between 900 and 1200$$^{circ}$$C, but that there was significant degradation in tensile strength of 9Cr-ODS steel claddings above 1200$$^{circ}$$C. This degradation was attributed to grain boundary sliding deformation with $$gamma$$/$$delta$$ transformation, which was associated with reduced ductility. On the other hand, tensile strength of recrystallized 12Cr-ODS and FeCrAl-ODS steel claddings retained its high value above 1200 $$^{circ}$$C unlike the other tested materials. Present study includes the result of "R&D of ODS ferritic steel fuel cladding for maintaining fuel integrity at the high temperature accident condition" entrusted to Hokkaido University by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT).

Journal Articles

Development of phase rotation system for RF-chopper at J-PARC Linac

Futatsukawa, Kenta*; Kobayashi, Tetsuya*; Sato, Fumiaki; Shinozaki, Shinichi; Chishiro, Etsuji; Hirano, Koichiro; Fang, Z.*; Fukui, Yuji*; Hori, Toshihiko; Michizono, Shinichiro*

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1317 - 1320, 2015/09

In the J-PARC linac, an RF deflector installed in 3-MeV Medium Energy Beam Transport (MEBT1) is used to kick the unnecessary beam and the intermediate-pulse like a comb is created. The kicked beam leads to a scraper downstream the RF deflector and lose all kinetic energy. When the beam current increases to 50 mA of the design value, the heat load of a scraper to irradiate the kicked beam increases and its surface is predicted to be damaged. Therefore, we are preparing the tandem scrapers to reduce the damage. The half of the kicked beam leads to a scraper and the residual is to the other. The chopping operation is achieved by rotating the phase of the RF deflector in the periodic cycles by the LLRF system. We will introduce the phase rotation system and the test results.

Journal Articles

Status of J-PARC linac LLRF after the Tohoku Earthquake

Futatsukawa, Kenta*; Anami, Shozo*; Kobayashi, Tetsuya*; Fang, Z.*; Fukui, Yuji*; Michizono, Shinichiro*; Kawamura, Masato*; Sato, Fumiaki; Shinozaki, Shinichi; Chishiro, Etsuji; et al.

Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.769 - 773, 2013/08

no abstracts in English

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.

Journal Articles

Compact DEMO, SlimCS; Design progress and issues

Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Kawashima, Hisato; Kurita, Genichi; Tanigawa, Hiroyasu; Nakamura, Hirofumi; Honda, Mitsuru; Saito, Ai*; Sato, Satoshi; et al.

Nuclear Fusion, 49(7), p.075029_1 - 075029_10, 2009/07

 Times Cited Count:135 Percentile:97.73(Physics, Fluids & Plasmas)

Recent design study on SlimCS focused mainly on the torus configuration including blanket, divertor, materials and maintenance scheme. For vertical stability of elongated plasma and high beta access, a sector-wide conducting shell is arranged in between replaceable and permanent blanket. The reactor adopts pressurized-water-cooled solid breeding blanket. Compared with the previous advanced concept with supercritical water, the design options satisfying tritium self-sufficiency are relatively scarce. Considered divertor technology and materials, an allowable heat load to the divertor plate should be 8 MW/m$$^{2}$$ or lower, which can be a critical constraint for determining a handling power of DEMO (a combination of alpha heating power and external input power for current drive).

Journal Articles

Performance of J-PARC linac RF system

Kobayashi, Tetsuya; Chishiro, Etsuji; Hori, Toshihiko; Suzuki, Hiroyuki; Yamazaki, Masayoshi; Anami, Shozo*; Fang, Z.*; Fukui, Yuji*; Kawamura, Masato*; Michizono, Shinichiro*; et al.

Proceedings of 2007 Particle Accelerator Conference (PAC '07) (Internet), p.2128 - 2130, 2007/08

High power operation of all the RF systems of J-PARC linac was started for the cavity conditioning in October 2006. Twenty 324-MHz klystrons have supplied the power to the accelerating cavities successfully, and the beam commissioning was started in November 2006. The RF drive and control systems are working well, and required stability is satisfied.

Journal Articles

Performance of J-PARC LINAC RF system

Kobayashi, Tetsuya; Chishiro, Etsuji; Hori, Toshihiko; Suzuki, Hiroyuki; Yamazaki, Masayoshi; Anami, Shozo*; Fang, Z.*; Fukui, Yuji*; Kawamura, Masato*; Michizono, Shinichiro*; et al.

Proceedings of 4th Annual Meeting of Particle Accelerator Society of Japan and 32nd Linear Accelerator Meeting in Japan (CD-ROM), p.510 - 512, 2007/00

High power operation of all the RF systems of J-PARC linac was started for the cavity conditioning in October 2006. Twenty 324-MHz klystrons have supplied the power to the accelerating cavities successfully. The beam commissioning was started in November 2006 then the acceleration to the design energy of 181 MeV was succeeded. The injection to the 3-GeV synchrotron will be started in September 2007. The RF control systems are performing according to the expectation, and the required field stability is satisfied.

Journal Articles

Status of RF system for the J-PARC linac

Chishiro, Etsuji; Hori, Toshihiko*; Kobayashi, Tetsuya; Suzuki, Hiroyuki*; Suganuma, Kazuaki; Yamazaki, Masayoshi*; Anami, Shozo*; Fang, Z.*; Fukuda, Shigeki*; Fukui, Yuji*; et al.

Proceedings of 2nd Annual Meeting of Particle Accelerator Society of Japan and 30th Linear Accelerator Meeting in Japan, p.236 - 238, 2005/07

no abstracts in English

Journal Articles

The Summary report on engineering design activities in the International Thermonuclear Experimental Reactor (ITER) project

Mori, Masahiro; Shoji, Teruaki; Araki, Masanori; Saito, Keiji*; Senda, Ikuo; Omori, Junji*; Sato, Shinichi*; Inoue, Takashi; Ono, Isamu*; Kataoka, Takahiro*; et al.

Nihon Genshiryoku Gakkai-Shi, 44(1), p.16 - 89, 2002/01

no abstracts in English

Journal Articles

Experimental verification and analysis of neutron streaming effect through void holes for control rod insertion in HTTR

Akino, Fujiyoshi; Takeuchi, Motoyoshi; Ono, Toshihiko; Kaneko, Yoshihiko

Journal of Nuclear Science and Technology, 34(2), p.185 - 192, 1997/02

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

VHTRC experiment for verification test of H$$infty$$ reactivity estimation method

Fujii, Yoshio; Suzuki, Katsuo; Akino, Fujiyoshi; Yamane, Tsuyoshi; Fujisaki, Shingo; Takeuchi, Motoyoshi; Ono, Toshihiko

JAERI-Data/Code 96-001, 102 Pages, 1996/02

JAERI-Data-Code-96-001.pdf:2.32MB

no abstracts in English

Journal Articles

Measurement of control rod reactivity worth in axially heterogeneous fuel core (VHTRC-4) by PNS method

Akino, Fujiyoshi; Takeuchi, Motoyoshi; Ono, Toshihiko; Fujisaki, Shingo

PHYSOR 96: Int. Conf. on the Physics of Reactors, 2, p.E281 - E289, 1996/00

no abstracts in English

Journal Articles

Measurement of effective delayed neutron fraction of VHTRC-1 core

Akino, Fujiyoshi; Takeuchi, Motoyoshi; Ono, Toshihiko

Journal of Nuclear Science and Technology, 31(8), p.861 - 863, 1994/08

 Times Cited Count:4 Percentile:53.92(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Construction of VHTRC(Very High Temperature Reactor Critical Assembly)

; Akino, Fujiyoshi; Yamane, Tsuyoshi; ; Kitadate, Kenji; ; Takeuchi, Motoyoshi; Ono, Toshihiko; Kaneko, Yoshihiko

JAERI 1305, 138 Pages, 1987/08

JAERI-1305.pdf:5.59MB

no abstracts in English

Oral presentation

RF system for J-PARC linac

Chishiro, Etsuji; Suzuki, Hiroyuki; Yamazaki, Masayoshi; Hori, Toshihiko; Kobayashi, Tetsuya; Fukui, Yuji*; Kawamura, Masato*; Fang, Z.*; Yamaguchi, Seiya*; Anami, Shozo*; et al.

no journal, , 

The RF compoments of the J-PARC linac have been installed in the building, and the evaluation of each compoment was started. In this workshop, we report the recent status and R&D results of the RF system.

Oral presentation

Progress in DEMO R&D activities within the BA-IFERC project

Hayashi, Kimio; Araki, Masanori; Baluc, N.*; Yamanishi, Toshihiko; Nishitani, Takeo; Hernandez, T.*; Morono, A.*; Moriani, A.*; Tosti, S.*; Nozawa, Takashi; et al.

no journal, , 

The Broader Approach (BA) activities have started in mid 2007. The DEMO R&D activities are intended to support the BA activities for design of fusion demonstration reactor (DEMO). The progress so far in the DEMO R&D activities is presented in this conference. Based on the common interest of the EU and Japan towards DEMO, current activities are smoothly proceeding in the following five areas: (1) SiC/SiC composites, (2) Tritium technology, (3) Materials engineering for DEMO blanket, (4) Advanced neutron multiplier, and (5) Advanced tritium breeders. From 2010 these R&D activities will be accelerated, after the preparation of the experimental equipment and facilities is completed.

Oral presentation

Fluorescence from Ar$$_2$$ excimer using EUV free electron laser

Nishi, Ryosuke*; Minami, Yuki*; Yamanoi, Kohei*; Nakazato, Tomoharu*; Shimizu, Toshihiko*; Sarukura, Nobuhiko*; Iwayama, Hiroshi*; Shigemasa, Eiji*; Harries, J.; Nagasono, Mitsuru*

no journal, , 

no abstracts in English

27 (Records 1-20 displayed on this page)