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Journal Articles

Progress of divertor simulation research toward the realization of detached plasma using a large tandem mirror device

Nakashima, Yosuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Oki, Kensuke*; Sakamoto, Mizuki*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; Imai, Tsuyoshi*; et al.

Journal of Nuclear Materials, 463, p.537 - 540, 2015/08

 Times Cited Count:18 Percentile:84.56(Materials Science, Multidisciplinary)

Journal Articles

Development of divertor simulation research in the GAMMA 10/PDX tandem mirror

Nakashima, Yosuke*; Sakamoto, Mizuki*; Yoshikawa, Masayuki*; Oki, Kensuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; et al.

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Journal Articles

Evaluation of inter-laminar shear strength of GFRP composed of bonded glass/polyimide tapes and cyanate-ester/epoxy blended resin for ITER TF coils

Hemmi, Tsutomu; Nishimura, Arata*; Matsui, Kunihiro; Koizumi, Norikiyo; Nishijima, Shigehiro*; Shikama, Tatsuo*

AIP Conference Proceedings 1574, p.154 - 161, 2014/01

 Times Cited Count:6 Percentile:93.37

Japan Atomic Energy Agency (JAEA), as Japan Domestic Agency, has responsibility to procure 9 ITER Toroidal Field (TF) coils. The insulation system of the ITER TF coils consists of 3 layers of insulations, which are a conductor insulation, a double-pancake (DP) insulation and a ground insulation, composed of multi-layer glass/polyimide tapes impregnated a resin. The ITER TF coils are required to withstand an irradiation of 10 MGy from $$gamma$$-ray and neutrons since the ITER TF coils is exposed by first neutron ($$>$$ 0.1 MeV) of 10$$^{22}$$ n/m$$^{2}$$ during the operation of 20 years in the ITER. Cyanate-ester/epoxy blended resins and bonded glass/polyimide tapes are developed as insulation materials to realize the required radiation-hardness for the insulation of the ITER TF coils. To evaluate the radiation-hardness of the developed insulation materials, the inter-laminar shear strength of glass-fiber reinforced plastics (GFRP) fabricated using developed insulation materials is measured as one of most important mechanical properties before/after the irradiation in a fission reactor of JRR-3. As a result, it is demonstrated that the GFRPs using the developed insulation materials have a sufficient performance to apply the ITER TF coil insulation.

Journal Articles

Competition between magnetic ordering and random spin freezing in Dy$$_2$$PtS$$_3$$

Li, D.*; Yamamura, Tomoo*; Homma, Yoshiya*; Yubuta, Kunio*; Shikama, Tatsuo*; Aoki, Dai*; Nimori, Shigeki*; Haga, Yoshinori

Journal of the Korean Physical Society, 62(12), p.2233 - 2238, 2013/06

 Times Cited Count:3 Percentile:28.07(Physics, Multidisciplinary)

Journal Articles

Development and application of radiation-resistant optical fiber for heavy irradiation environment

To, Kentaro; Shikama, Tatsuo*

Reza Kenkyu, 41(5), p.332 - 336, 2013/05

There are fewer devices which have a long-term stability used in a heavy irradiation environment such as nuclear power plant and accelerator. And, the nuclear accident at Fukushima-1 revealed importance of visualization of core parts of nuclear systems, where heavy radiation field will hider easy access. Fused silica based optical fibers will be one among the strongest candidates for visualization of the fields. The paper will describe the present status of development and its application of radiation resistant optical fibers.

Journal Articles

Japanese contribution to the DEMO-R&D program under the Broader Approach activities

Nishitani, Takeo; Yamanishi, Toshihiko; Tanigawa, Hiroyasu; Nozawa, Takashi; Nakamichi, Masaru; Hoshino, Tsuyoshi; Koyama, Akira*; Kimura, Akihiko*; Hinoki, Tatsuya*; Shikama, Tatsuo*

Fusion Engineering and Design, 86(12), p.2924 - 2927, 2011/12

 Times Cited Count:7 Percentile:50.3(Nuclear Science & Technology)

Several technical R&D activities related to the blanket materials are newly launched as a part of the Broader Approach (BA) activities, which was initiated by the EU and Japan. According to the common interests of these parties for DEMO, R&Ds on reduced activation ferritic/martensitic (RAFM) steels as structural material, SiCf/SiC composites as a flow channel insert material and/or alternative structural material, advanced tritium breeders and neutron multipliers, and tritium technology are carried out through the BA DEMO R&D program, in order to establish the technical bases on the blanket materials and the tritium technology required for DEMO design. This paper describes overall schedule of those R&D activities and recent progress in Japan carried out by JAEA as the domestic implementing agency on BA, collaborating with Japanese universities and other research institutes.

Journal Articles

Recent progress in blanket materials development in the Broader Approach Activities

Nishitani, Takeo; Tanigawa, Hiroyasu; Nozawa, Takashi; Jitsukawa, Shiro; Nakamichi, Masaru; Hoshino, Tsuyoshi; Yamanishi, Toshihiko; Baluc, N.*; M$"o$slang, A.*; Lindou, R.*; et al.

Journal of Nuclear Materials, 417(1-3), p.1331 - 1335, 2011/10

 Times Cited Count:14 Percentile:71.09(Materials Science, Multidisciplinary)

As a part of the Broader Approach (BA) activities, the research and development on blanket related materials and tritium technology have been initiated toward DEMO by Japan and EU. Recently, those five R&D items have progressed substantially in Japan and EU. As a preparatory work aiming at the RAFM steel muss-production development, a 5-ton heat of RAFM steel (F82H) was procured with the Electro Slag Re-melting as a secondary melting. The result of the double notch tensile test method for the NITE-SiC$$_{f}$$/SiC specimen indicated notch insensitivity and very minor size effect on proportional limit tensile stress and fracture strength. For the fabrication technology development of beryllide neutron multiplayer pebbles, Be- Ti inter-metallic pebbles have been sintered directly from the mixed powder of Be and Ti in Japan.

Journal Articles

Effects of neutrons and gamma-rays on polymethylmethacrylate plastic optical fiber

To, Kentaro; Sakasai, Kaoru; Nakamura, Tatsuya; Soyama, Kazuhiko; Shikama, Tatsuo*

Journal of Nuclear Materials, 417(1-3), p.814 - 817, 2011/10

 Times Cited Count:9 Percentile:58.76(Materials Science, Multidisciplinary)

Plastic optical fibers (POFs) are very useful and widely used for signal transmission because they have the following advantages: (1) they do not produce electrical noise, (2) they are inexpensive and lightweight, and (3) they have wide optical signal bands. In this study, the effects of 14-MeV neutron and $$gamma$$-ray irradiation on a POF were investigated. Strong radiation damage (radiation-induced transmission loss) was caused by irradiation with both neutrons and $$gamma$$-rays, particularly at short wavelengths. To determine the effects of neutron and $$gamma$$-ray irradiation, the amount of energy absorbed in the PMMA POF was calculated by using a Monte Carlo simulation using PHITS code. The similar radiation effect with both neutrons and $$gamma$$-rays was observed at an absorbed energy less than 5$$times$$10$$^{16}$$ eV.

Journal Articles

Evidence for spin-glass state in nonmagnetic atom disorder compound Pr$$_2$$AgIn$$_3$$

Li, D. X.*; Yamamura, Tomoo*; Yubuta, Kunio*; Nimori, Shigeki*; Haga, Yoshinori; Shikama, Tatsuo*

Journal of Physics; Conference Series, 320, p.012041_1 - 012041_6, 2011/09

 Times Cited Count:8 Percentile:87.62

Journal Articles

Feasibility study on cryogenic irradiation facility in JMTR

Inaba, Yoshitomo; Tsuchiya, Kunihiko; Shikama, Tatsuo*; Nishimura, Arata*; Kawamura, Hiroshi

Fusion Engineering and Design, 86(2-3), p.134 - 140, 2011/03

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

The Japan Materials Testing Reactor (JMTR) of the Japan Atomic Energy Agency is a testing reactor with first criticality in March 1968. The reactor has been utilized for various neutron irradiation tests on nuclear fuels and materials, as well as for radioisotope production. The operation of JMTR stopped temporarily in August 2006 for refurbishment and improvement. The renewed JMTR will resume operation in Japanese fiscal year 2011. For the resumption of the new JMTR, the new irradiation facilities, the usability improvements, the target, and the expected roles of the new JMTR have been discussed. As one of the new irradiation facilities, the cryogenic irradiation facility, which is used for the investigation on the low-temperature irradiation behavior of materials such as superconducting magnet materials for fusion reactors, has been desired. In this study, the feasibility of low-temperature irradiation tests with the cryogenic irradiation facility was investigated, and the conceptual design of the facility was carried out. As a result, it was found that irradiation tests at temperatures below 20 K for the development of the superconducting magnet materials can be realized by the installation of an irradiation capsule into an irradiation hole with low $$gamma$$ heating and by the adoption of vacuum jacketed tubes to connect between the capsule and a cooling system.

Journal Articles

Magnetic anisotropy and spin-glass behavior in single crystalline U$$_2$$PdSi$$_3$$

Li, D. X.*; Kimura, Akihiro*; Haga, Yoshinori; Nimori, Shigeki*; Shikama, Tatsuo*

Journal of Physics; Condensed Matter, 23(7), p.076003_1 - 076003_7, 2011/02

 Times Cited Count:12 Percentile:48.12(Physics, Condensed Matter)

Journal Articles

Ion irradiation effects on the optical properties of tungsten oxide films

Nagata, Shinji*; Fujita, Haruka*; Inoue, Aichi; Yamamoto, Shunya; Tsuchiya, Bun*; Shikama, Tatsuo*

Nuclear Instruments and Methods in Physics Research B, 268(19), p.3151 - 3154, 2010/10

 Times Cited Count:3 Percentile:29.26(Instruments & Instrumentation)

A tungsten tri-oxide (WO$$_{3}$$) film covered with a thin catalyst layer is one of the candidates for hydrogen sensing devices that show a reversible coloration under hydrogen exposure. While the injection of the cations and/or the formation of the oxygen vacancies can be responsible for the coloration of the film, the mechanism of the gasochromic phenomenon is not fully understood. In the present work, the changes of the optical properties in the WO$$_{3}$$ film by ion irradiation were investigated to clarify the relation between the coloration and oxygen vacancies. WO$$_{3}$$ films of 300-500 nm thicknesses were deposited on SiO$$_{2}$$ substrates by magnetron sputtering. Oxygen ions at energies between 200 and 800 keV were irradiated to the WO$$_{3}$$ films. The optical absorption of the film was measured in the wavelengths between 190 and 1000 nm. The results show that the change of optical-absorption coefficient in WO$$_{3}$$ films depends on both electronic and nuclear stopping powers.

Journal Articles

Fission neutron irradiation effect on interlaminar shear strength of cyanate ester resin GFRP at RT and 77 K

Nishimura, Arata*; Izumi, Yoshinobu*; Nishijima, Shigehiro*; Hemmi, Tsutomu; Koizumi, Norikiyo; Takeuchi, Takao*; Shikama, Tatsuo*

AIP Conference Proceedings 1219, p.127 - 134, 2010/04

 Times Cited Count:1 Percentile:51.09

A GFRP with cyanate ester resin was fabricated and neutron irradiation tests up to 1$$times$$10$$^{22}$$ n/m$$^{2}$$ of fast neutron with over 0.1 MeV energy were carried out in fission reactor. The fabrication process of cyanate ester GFRP was established and a collaboration network to perform investigations on irradiation effect of superconducting magnet materials was constructed. Three kinds of samples were fabricated. The first was CTD403 GFRP made by NIFS, the second was (cyanate ester + epoxy) GFRP provided by Toshiba, and the last was CTD403 GFRP made by Toshiba. The irradiation was carried out at JRR-3 in Japan Atomic Energy Agency using Rabbit capsules. After the irradiation, short beam tests were conducted at room temperature and 77 K and interlaminar shear strength (ILSS) was evaluated. The irradiation of 1$$times$$10$$^{21}$$ n/m$$^{2}$$ increased ILSS a little but 1$$times$$10$$^{22}$$ n/m$$^{2}$$ irradiation decreased ILSS to around 50 MPa. These tendencies were observed in all three kinds of GFRPs.

Journal Articles

Fusion materials development program in the Broader Approach activities

Nishitani, Takeo; Tanigawa, Hiroyasu; Jitsukawa, Shiro; Nozawa, Takashi; Hayashi, Kimio; Yamanishi, Toshihiko; Tsuchiya, Kunihiko; M$"o$slang, A.*; Baluc, N.*; Pizzuto, A.*; et al.

Journal of Nuclear Materials, 386-388, p.405 - 410, 2009/04

 Times Cited Count:31 Percentile:88.73(Materials Science, Multidisciplinary)

The establishment of the breeding blanket technology is one of the most important engineering issues on the DEMO development. For the DEMO blanket, developments of the structural materials and functional materials such as tritium breeder and neutron multiplier. Which should be used under the savior circumstance such as high neutron fluence, high temperature and strong magnetic field, are urgent issues. In the Broader Approach activities initiated by EU and Japan, developments of reduced activation ferritic martensitic steels as a DEMO blanket structural material, SiC/SiC composites, advanced tritium breeders and neutron multiplier for DEMO blankets, are planed as common interest issues of EU and Japan. This paper describes the overview of the development program.

Journal Articles

Effect of 14-MeV neutrons on strontium-aluminate-based long-lasting phosphor

To, Kentaro; Shikama, Tatsuo*; Katsui, Hirokazu*; Nagata, Shinji*; Tsuchiya, Bun*; Yamauchi, Michinori*; Nishitani, Takeo

Journal of Nuclear Materials, 386-388, p.1027 - 1029, 2009/04

 Times Cited Count:4 Percentile:31.45(Materials Science, Multidisciplinary)

Fluorescence and long-lasting emission properties of two types of Long-lasting phosphors (LLPs), SrAl$$_{2}$$O$$_{4}$$:Eu$$^{2+}$$,Dy$$^{3+}$$ and Sr$$_{4}$$Al$$_{14}$$O$$_{25}$$:Eu$$^{2+}$$,Dy$$^{3+}$$, were examined under 14-MeV neutron irradiation. The fluorescent spectra of the LLPs have characteristic peaks due to their dopants and the fluorescent intensity of Sr$$_{4}$$Al$$_{14}$$O$$_{25}$$:Eu$$^{2+}$$,Dy$$^{3+}$$ shows good radiation resistance for the neutrons fluence up to 10$$^{19}$$ n/m$$^{2}$$. Long-lasting emissions are exhibited after neutron irradiation, and the emission spectra have one peak due to Eu$$^{2+}$$. Further, it is found that there is an optimum neutron fluence at which the longest decay time is obtained.

Journal Articles

Damage process and luminescent characteristics in silica glasses under ion irradiation

Nagata, Shinji*; Katsui, Hirokazu*; Tsuchiya, Bun*; Inoue, Aichi; Yamamoto, Shunya; To, Kentaro; Shikama, Tatsuo*

Journal of Nuclear Materials, 386-388, p.1045 - 1048, 2009/04

 Times Cited Count:13 Percentile:65.91(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Hydrogen retention induced by ion implantation in tungsten trioxide films

Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Yoshikawa, Masahito; Shikama, Tatsuo*

Nuclear Instruments and Methods in Physics Research B, 267(8-9), p.1480 - 1483, 2009/03

 Times Cited Count:12 Percentile:63.47(Instruments & Instrumentation)

We quantitatively studied the relation between hydrogen retention and optical properties induced by hydrogen ion implantation in tungsten trioxide (WO$$_{3}$$) films. Films of WO$$_{3}$$ (300 nm) covered with tungsten metal layers (200 nm) were prepared on transparent SiO$$_{2}$$ substrates by a reactive sputtering in Ar and O$$_{2}$$ mixture. When H$$_{2}$$$$^{+}$$ ions were implanted into the samples at an acceleration voltage of 10 kV, the concentration of hydrogen retaining in the WO$$_{3}$$ films increased up to 0.4 H/W in proportion to the fluence of H$$_{2}$$$$^{+}$$ ions. The optical absorption coefficient at 750 nm of samples increased linearly by 3 $$mu$$m$$^{-1}$$ with increasing the concentration of hydrogen implanted up to 0.1 H/W. And then, increased and saturated at 4 $$mu$$m$$^{-1}$$ with the increase of hydrogen concentration higher than 0.1 H/W. It was found that the hydrogen retention up to 0.1 H/W in tungsten trioxide layers can be monitored by measuring the optical absorbance.

Journal Articles

Ion induced structural modification and nano-crystalline formation of Zr-Al-Ni-Cu metallic glasses

Nagata, Shinji*; Sasase, Masato*; Takahiro, Katsumi*; Tsuchiya, Bun*; Inoue, Aichi; Yamamoto, Shunya; Shikama, Tatsuo*

Nuclear Instruments and Methods in Physics Research B, 267(8-9), p.1514 - 1517, 2009/03

 Times Cited Count:9 Percentile:54.57(Instruments & Instrumentation)

In this study, effects of the ion implantation on the phase transformation and nano-crystalline formation were examined in Zr-based metallic glasses. Samples were 2 mm thick plates and thin films of Zr$$_{55}$$Al$$_{10}$$Ni$$_{5}$$Cu$$_{30}$$ prepared by casting in a copper mold and by using RF magnetron sputtering, respectively. Ions of Mg, P, Au and Bi with 100-500 keV were implanted in the samples up to 2 $$times$$ 10$$^{16}$$ ions/cm$$^{2}$$ at room temperature. Nano-crystalline structure was found in implanted samples by TEM observation, while the long-range order in the structure was not found for the X-ray diffraction patterns. The electron diffraction patterns indicated the formation of fcc-Zr$$_{2}$$Cu in the P, Au, and Bi implanted region. Changes of the binding energy of the core level electron and valence band structure suggested the formation of Au-Zr or Au-Cu alloys in the Au ion implanted region.

Journal Articles

Status of development of functional materials with perspective on beyond-ITER

Shikama, Tatsuo*; Knitter, R.*; Konys, J.*; Muroga, Takeo*; Tsuchiya, Kunihiko; M$"o$slang, A.*; Kawamura, Hiroshi; Nagata, Shinji*

Fusion Engineering and Design, 83(7-9), p.976 - 982, 2008/12

 Times Cited Count:37 Percentile:90.79(Nuclear Science & Technology)

Functional materials should play an important role not only in ITER but also in fusion machines beyond ITER, though it is occasionally claimed that future fusion plants should have much more simple structures and they should be free from auxiliary systems such as diagnostics. Studies on test blanket modules (TBM) clearly show the importance of functional materials there. The paper will review the present status of studies and developments of functional ceramics for nuclear fusion applications, with a perspective on their application in electric-power generating fusion power plant, namely DEMO.

Journal Articles

Effects of catalyst on gasochromic properties in tungsten oxide films

Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Yoshikawa, Masahito; Shikama, Tatsuo*

Transactions of the Materials Research Society of Japan, 33(4), p.1127 - 1130, 2008/12

We investigated effects of catalyst on gasochromic properties in tungsten oxide films. Amorphous WO$$_{3}$$ films coated with Pd and Pt catalysts were prepared on SiO$$_{2}$$ substrates by employing reactive RF magnetron sputtering. The field emission scanning electron microscope (FE-SEM) showed that particles with a dozes nm diameter of Pd and with a few nm of Pt grew on the surface at beginning of deposition. The continuous catalytic layers were observed with increasing the amounts of more than 2 nm for Pd and 0.2 nm for Pt catalysts, respectively. When the continuous layers formed on WO$$_{3}$$ surface, the excellent gasochromic properties were obtained. The results indicated that Pt catalysts were suitable for high sensitive hydrogen sensors consisting of gasochromic WO$$_{3}$$ films.

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