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Journal Articles

Suppression of vacancy formation and hydrogen isotope retention in irradiated tungsten by addition of chromium

Wang, J.*; Hatano, Yuji*; Toyama, Takeshi*; Suzudo, Tomoaki; Hinoki, Tatsuya*; Alimov, V. Kh.*; Schwarz-Selinger, T.*

Journal of Nuclear Materials, 559, p.153449_1 - 153449_7, 2022/02

 Times Cited Count:2 Percentile:59.27(Materials Science, Multidisciplinary)

To study the effect of the content of chromium (Cr) in the tungsten (W) matrix on the vacancy formation and retention of hydrogen isotopes, the samples of the W-0.3Cr alloy were irradiated with 6.4 MeV Fe ions in the temperature range of 523-1273 K. These displacement-damaged samples were exposed to D$$_{2}$$ gas at a temperature of 673 K. The addition of 0.3% Cr into the W matrix resulted in a significant decrease in the retention of deuterium compared to pure W after irradiation especially at high temperature. Positron lifetime for W-0.3Cr alloy irradiated at 1073 K was almost similar to that for non-irradiated one. These facts indicate the suppression of the formation of vacancy-type defects by 0.3% Cr addition.

Journal Articles

Development of high-grade VPS-tungsten coatings on F82H reduced activation steel

Tokunaga, Tomonori*; Watanabe, Hideo*; Yoshida, Naoaki*; Nagasaka, Takuya*; Kasada, Ryuta*; Lee, Y.-J.*; Kimura, Akihiko*; Tokitani, Masayuki*; Mitsuhara, Masatoshi*; Hinoki, Tatsuya*; et al.

Journal of Nuclear Materials, 442(1-3), p.S287 - S291, 2013/11

 Times Cited Count:10 Percentile:61.45(Materials Science, Multidisciplinary)

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:49.27(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

Tensile, compressive and in-plane/inter-laminar shear failure behavior of CVI- and NITE-SiC/SiC composites

Nozawa, Takashi; Choi, Y.-B.*; Hinoki, Tatsuya*; Kishimoto, Hirotatsu*; Koyama, Akira*; Tanigawa, Hiroyasu

IOP Conference Series; Materials Science and Engineering, 18, p.162011_1 - 162011_4, 2011/09

 Times Cited Count:9 Percentile:96.51

A SiC/SiC composite is one of attractive candidates for fission and nuclear fusion due to the proven irradiation tolerance coupled with the excellent baseline properties as refractory ceramics. Considering the inherent anisotropy of composites due to the variety of fabric architecture, it is required to identify the crack propagation behavior of SiC/SiC composites by various failure modes. This study aims to evaluate crack propagation behavior by the axial and off-axial tensile/compressive tests, Iosipescu test for in-plane shear, double-notch-shear test for inter-laminar shear and diametral compression test for inter-laminar detachment. Preliminary test results identified strength anisotropy maps, implying that the composites failed by the mixed modes. Specifically, it was found that the in-plane/inter-laminar shear modes had significant impacts on the results.

Journal Articles

Recent advances and issues in development of silicon carbide composites for fusion applications

Nozawa, Takashi; Hinoki, Tatsuya*; Hasegawa, Akira*; Koyama, Akira*; Kato, Yutai*; Snead, L. L.*; Henager, C. H. Jr.*; Hegeman, J. B. J.*

Journal of Nuclear Materials, 386-388, p.622 - 627, 2009/04

 Times Cited Count:112 Percentile:99.2(Materials Science, Multidisciplinary)

A new class SiC/SiC composite have been developed for fusion. While the development efforts has resulted in a radiation-resistant SiC/SiC, development continues to improve on engineering properties of this composite. With the completion of the "proof-of-principal" phase, the R&D on SiC/SiC is now shifting to the more pragmatic phase of material data-basing. Critical application issues still remain, including (1) heavy irradiation effect with considerations of He/H synergistic effects and irradiation creep, (2) erosion-corrosion behavior, (3) nuclear transmutation other than He/H, and (4) joining. Understanding the irradiation effect on electrical conductivity is another important issue for the FCI application. Along with the review in material development, characterization, and irradiation effect studies, this paper provides an introductive work toward standardization of the test methodology.

Journal Articles

Evaluation on failure resistance to develop design basis for quasi-ductile silicon carbide composites for fusion application

Nozawa, Takashi; Hinoki, Tatsuya*; Koyama, Akira*; Tanigawa, Hiroyasu

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Silicon carbide composites (SiC/SiC) are promising candidate materials for fusion reactors with advanced features such as high thermal efficiency. This paper will provide a present status in development of design basis for quasi-ductile SiC/SiC as a structural application. For that purpose, failure behavior, i.e., matrix cracking behavior, of a new class of radiation-resistant SiC/SiC, e.g., a nano-infiltration transient-eutectic phase (NITE) SiC/SiC, was evaluated. With a fact of the notch-insensitivity and very minor size effect on the failure behavior, a stress criterion is suggested in failure of NITE-SiC/SiC.

Journal Articles

Fabrication of SiC fiber reinforced SiC composite by chemical vapor infiltration for excellent mechanical properties

Igawa, Naoki; Taguchi, Tomitsugu; Nozawa, Takashi*; Snead, L. L.*; Hinoki, Tatsuya*; McLaughlin, J. C.*; Kato, Yutai*; Jitsukawa, Shiro; Koyama, Akira*

Journal of Physics and Chemistry of Solids, 66(2-4), p.551 - 554, 2005/02

 Times Cited Count:45 Percentile:82.59(Chemistry, Multidisciplinary)

Silicon carbide is an important engineering ceramic because of its high strength and stability at high temperature and low induced radioactivity after neutron irradiation. Though monolithic SiC is brittle and low toughness, SiC fiber reinforced SiC matrix composites significantly improve these properties and therefore are attractive candidate materials for fusion reactor structural applications. Recently, stoichiometric SiC fibers with superior mechanical properties have been produced. We carried out the optimization of interface and composite fabrication using the chemical vapor infiltration, which is the one of the best techniques to fabricate the SiC composite. The composite with higher density and homogeneous matrix was obtained by the optimization of materials and carrier gas flow rate. The porosity was decreased with increasing the fiber volume fraction. We adopted the carbon or carbon/SiC interface between fiber and matrix and we found that the dependence of interface thickness on the tensile properties was small in the interface thickness from 50 to 300 nm.

Journal Articles

Fabrication of advanced SiC fiber/F-CVI SiC matrix composites with SiC/C multi-layer interphase

Taguchi, Tomitsugu; Nozawa, Takashi*; Igawa, Naoki; Kato, Yutai*; Jitsukawa, Shiro; Koyama, Akira*; Hinoki, Tatsuya*; Snead, L. L.*

Journal of Nuclear Materials, 329-333(Part1), p.572 - 576, 2004/08

 Times Cited Count:46 Percentile:93.02(Materials Science, Multidisciplinary)

The SiC/SiC composite with SiC/C multi-layer interphase coated on advanced SiC fibers was fabricated by the forced thermal-gradient chemical vapor infiltration (F-CVI) process for improvement in mechanical properties. The SEM and TEM observation verified that SiC/C multi-layer interphase was formed on SiC fibers. The both flexural and tensile strengths of SiC/SiC composite with SiC/C multi-layer interphase were approximately 10 % higher than that with single carbon interphase. The SEM observation on the fracture surface of the composite with SiC/C multi-layer reveals that cylindrical steps around the fiber were formed. The several crack deflections occurred within SiC/C multi-layer interphase. The SiC/C multi-layer applied in this study operated efficiently to improve the mechanical properties.

Oral presentation

Development of high temperature fusion blanket with LiPb-SiC and its socio-economic aspects

Konishi, Satoshi*; Yamamoto, Yasushi*; Hinoki, Tatsuya*; Koyama, Akira*; Enoeda, Mikio

no journal, , 

no abstracts in English

Oral presentation

Evaluation of advanced materials for liquid Li-Pb blanket environment

Niigawa, Satoshi*; Ueno, Yukihisa*; Enoeda, Mikio; Hinoki, Tatsuya*; Park, J.*; Yamamoto, Yasushi*; Konishi, Satoshi*

no journal, , 

no abstracts in English

Oral presentation

Development of burn-up fuel for gas-cooled fast reactor(GFR), 5; Thermal characterization and microstructure observation of the component

Donomae, Takako; Miwa, Shuhei; Park, J. S.*; Hinoki, Tatsuya*

no journal, , 

The examination on composite fuel assembly using the nitride fuel in which thermal efficiency is high as a promising candidacy for the high burn-up fuel for gas-cooled fast reactor(GFR) is advanced. In this report, heat characteristic tests and microstructure observation of composite fuel assembly using trial nitride fuel were carried out, and the problem which prepared draft in heat characteristics and production technique of the composite fuel was clarified.

Oral presentation

Development of high burn-up fuel for gas-cooled fast reactor (GFR), 2; Design of fuel element

Miwa, Shuhei; Donomae, Takako; Hinoki, Tatsuya*

no journal, , 

no abstracts in English

Oral presentation

Development of high burn-up fuel with SiC matrix for gas-cooled fast reactor

Hinoki, Tatsuya*; Park, Y.*; Park, J.*; Miwa, Shuhei; Donomae, Takako

no journal, , 

Nitride fuel and oxide fuel are candidate for helium gas-cooled fast reactor to achieve thermal efficiency over 40%. The conceptual design of fuel, which consists of nitride fuel of around 50%, highly dense SiC matrix and porous SiC buffer layers is encouraged according to the eport for "Feasibility Study on Commercialized Fast Reactor Cycle System (FS)", Japan. However there is no technique to form dense SiC in the small gap between fuels with accurate arrangement of fuels. The objective of this work is to develop basic fabrication technique for the high burn-up fuel utilizing forming technique for highly dense NITE-SiC/SiC composites. The cylindrical fuel is proposed in this work instead of spherical fuel to achieve high dense fuel and accurate arrangement.

Oral presentation

Development of high burn-up fuel for gas-cooled fast reactor (GFR), 2-2; Design of fuel elements, 2

Miwa, Shuhei; Donomae, Takako; Hinoki, Tatsuya*

no journal, , 

no abstracts in English

Oral presentation

Development of high burn-up fuel for gas-cooled fast reactor (GFR), 2-4; Microstructure evaluation of high burn-up fuel elements

Donomae, Takako; Miwa, Shuhei; Park, J. S.*; Hinoki, Tatsuya*

no journal, , 

Characteristics of the composite fuel assembly for the high burn-up fuel for the gas cooled fast breeder reactor were evaluated. By observing the microstructure from the viewpoint of the interface between SiC matrix in composite fuel assembly and buffer material, it became clear that there was the correlation between auxiliary segregation situation and strength characteristic. In addition, SiC matrix after the intensity test was also examined on the relation between microstructure and stress loading situation. As the result, there was the correlation in the growth agree with of existence and crystal grain of the stress loading.

Oral presentation

R&D on SiC/SiC composites in phase 1 for the BA activities; Evaluation of the failure behavior of SiC/SiC composites

Nozawa, Takashi; Choi, Y.-B.*; Hinoki, Tatsuya*; Tanigawa, Hiroyasu

no journal, , 

no abstracts in English

Oral presentation

Microstructure investigation on SiC by nano-infiltration transient eutectic process after triple ion beam bombardment

Ozawa, Kazumi; Koyanagi, Takaaki*; Taguchi, Tomitsugu; Nozawa, Takashi; Tanigawa, Hiroyasu; Kondo, Sosuke*; Hinoki, Tatsuya*

no journal, , 

A SiC/SiC composite is a promising candidate functional/structural material for fusion DEMO reactor. To examine the effects of transmuted H mainly on microstructural cavity formation, the monolithic NITE-SiC with 6wt% Y$$_{2}$$O$$_{3}$$-Al$$_{2}$$O$$_{3}$$ sintering additive system were ion-irradiated to 10 dpa at 1000$$^{circ}$$C nominally with 130 appmHe/dpa, and 40 or 400 appmH/dpa, respectively. In SiC grains, tiny cavities with 2 nm formed densely. However, it is revealed that H could not remarkably impact on cavity formation (size, density) in the condition studied. The influence of cavities formed along SiC-YAG grain boundary (GB) on cavity swelling seems to be also small, possibly attributed to its quite low density, even though the cavity size formed is three to five times larger than the size in CVI-SiC matrix in the same irradiation condition. Additional investigation of the microstructural evolution in YAG grain and SiC-YAG GB is a future plan.

Oral presentation

Effects of transmuted hydrogen on microstructure of SiC by nano-infiltration transient eutectic process after triple ion beam irradiation

Ozawa, Kazumi; Koyanagi, Takaaki*; Taguchi, Tomitsugu; Nozawa, Takashi; Tanigawa, Hiroyasu; Kondo, Sosuke*; Hinoki, Tatsuya*

no journal, , 

no abstracts in English

Oral presentation

Rupture properties of plain-woven Tyranno-SA3 CVI SiC/SiC composites

Ozawa, Kazumi; Nozawa, Takashi; Toyoshima, Kazuoki*; Tanigawa, Hiroyasu; Hinoki, Tatsuya*

no journal, , 

no abstracts in English

Oral presentation

Tensile deformation behavior of plain-woven Tyranno-SA3 CVI-composites at elevated temperatures

Ozawa, Kazumi; Nozawa, Takashi; Toyoshima, Kazuoki*; Tanigawa, Hiroyasu; Hinoki, Tatsuya*

no journal, , 

An advanced SiC/SiC composite is a promising candidate material for fusion DEMO blanket. Current study preliminarily aims to examine tensile deformation behavior of unirradiated advanced SiC/SiC composites tested at high temperatures. In rupture tests being concurrently conducted at 1000$$^{circ}$$C in vaccum, it was revealed that the plain-woven CVI-SiC matrix composite reinforced with Tyranno-SA3 fibers did not fail at 174 MPa (equivalent to 130% of PLS at 1000$$^{circ}$$C) for 1986 hours. Presently there was no negative sign of the notch effects, implying their good rupture property at certain conditions of concern.

22 (Records 1-20 displayed on this page)