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Nozawa, Takashi; Ozawa, Kazumi; Asakura, Yuki*; Koyama, Akira*; Tanigawa, Hiroyasu
Journal of Nuclear Materials, 455(1-3), p.549 - 553, 2014/12
Times Cited Count：15 Percentile：74.71(Materials Science, Multidisciplinary)SiC/SiC composite is a promising candidate material of fusion DEMO reactor. This paper aims to identify its damage tolerance and strength anisotropy by various characterization techniques such as acoustic emission (AE) monitoring, electrical resistivity (ER) measurement, and digital image correlation (DIC). The AE results identified that damage accumulation initiated prior to the proportional limit stress (PLS) by both tensile and compressive loadings for 2D composites. The preliminary AE waveform analysis implied that this AE detect strength corresponds to initiation of micro-cracking but the stress-strain curve shows further linearity due to the strong interfacial friction. Then fiber sliding occurred near the PLS, followed by the non-linearlity of the curve. The preliminary tensile test results using a notched specimen also suggest notch insensitivity of the composites in any loading directions. The detailed failure mechanism will eventually be discussed with ER and DIC results.
Nozawa, Takashi; Ozawa, Kazumi; Choi, Y.-B.*; Koyama, Akira*; Tanigawa, Hiroyasu
Fusion Engineering and Design, 87(5-6), p.803 - 807, 2012/08
Times Cited Count：29 Percentile：88.98(Nuclear Science & Technology)A SiC/SiC composite is a candidate material for a demonstration fusion power reactor. Considering the inherent anisotropy of composites with variety of fabric architecture is required to precisely predict axial and off-axial mechanical properties by various failure modes. This study evaluated crack propagation behavior by the various modes to provide a strength anisotropy map and we discussed a methodology to analytically predict this trend. The strength anisotropy maps identified for various fabric orientations clearly indicate that the composites failed by the mixed modes. Specifically, due to the axial anisotropy, five individual modes such as tensile/compressive strengths in the axial/transverse directions, respectively, as well as the in-plane shear strength, are identified to be essential. In this study, with the analytical criterion based on the Tsai-Wu model, the strength anisotropy could satisfactorily be described.
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：48.91(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.
Nishitani, Takeo; Tanigawa, Hiroyasu; Nozawa, Takashi; Jitsukawa, Shiro; Nakamichi, Masaru; Hoshino, Tsuyoshi; Yamanishi, Toshihiko; Baluc, N.*; M
slang, A.*; Lindou, R.*; et al.
Journal of Nuclear Materials, 417(1-3), p.1331 - 1335, 2011/10
Times Cited Count：14 Percentile：71.96(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
/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.
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：10 Percentile：96.47(Materials Science, Ceramics)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.
Nozawa, Takashi; Tanigawa, Hiroyasu; Park, J.-S.*; Koyama, Akira*
Proceedings of 33rd International Conference on Advanced Ceramics and Composites (CD-ROM), p.65 - 76, 2009/09
SiC/SiC composites are promising candidate materials for various energy industries. One of key issues for their practical application is to develop design basis of quasi-ductile composites. Understanding the crack propagation behavior is therefore essential. For this purpose, determining a fracture resistances undoubtedly important and this paper aims to evaluate this using various types of notched specimens. With the preliminary analysis by the authors, a new methodology to determine the fracture resistance has been developed based on the non-linear fracture mechanics, separately discussing the effect of irreversible energies. By adopting this method for nano-infiltration transient-eutectic-phase sintered (NITE) SiC/SiC composites, several key findings were obtained: (1) notch insensitivity, (2) no significant size effect, and (3) superior crack tolerance.
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：115 Percentile：99.19(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.
Nishitani, Takeo; Tanigawa, Hiroyasu; Jitsukawa, Shiro; Nozawa, Takashi; Hayashi, Kimio; Yamanishi, Toshihiko; Tsuchiya, Kunihiko; Mslang, A.*; Baluc, N.*; Pizzuto, A.*; et al.
Journal of Nuclear Materials, 386-388, p.405 - 410, 2009/04
Times Cited Count：31 Percentile：87.96(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.
Kim, S.-W.; Tanigawa, Hiroyasu; Hirose, Takanori; Koyama, Akira*
Journal of Nuclear Materials, 386-388, p.529 - 532, 2009/04
Times Cited Count：13 Percentile：64.74(Materials Science, Multidisciplinary)Low cycle fatigue (LCF) results at ambient temperature under diametral strain controlled conditions of the reduced activation ferritic/martensitic steel, F82H IEA heat before and after neutron irradiated samples are reported. The results show that cyclic softening behavior is the main mechanical feature observed in this material. A detailed analysis for the hysteresis loops was carried out to determine the friction and back stresses. The friction stress is equivalent to the resistance which the dislocations have to overcome to keep moving in the lattice. The back stress depends on the density of long-range impenetrable obstacles that are created by the dislocations movement such as pile-ups. The cyclic softening of F82H IEA heat is related with the decrease of the friction stress. Moreover, the friction and back stress behavior of neutron irradiated samples show significantly different behavior than those of unirradiated samples.
Tanigawa, Hiroyasu; Hirose, Takanori; Shiba, Kiyoyuki; Kasada, Ryuta*; Wakai, Eiichi; Serizawa, Hisashi*; Kawahito, Yosuke*; Jitsukawa, Shiro; Kimura, Akihiko*; Kono, Yutaka*; et al.
Fusion Engineering and Design, 83(10-12), p.1471 - 1476, 2008/12
Times Cited Count：78 Percentile：97.72(Nuclear Science & Technology)Reduced activation ferritic/martensitic steels (RAFMs) are recognized as the primary candidate structural materials for fusion blanket systems. F82H, which were developed and studied in Japan, was designed with an emphasis on high temperature properties and weldability. The database on F82H properties is currently the most extensive available among the existing RAFMs. The objective of this paper is to review the R&D status of F82H and to identify the key technical issues for the fabrication of an ITER Test Blanket Module (TBM) suggested by recent achievements in Japan.
Shibayama, Tamaki*; Kishimoto, Hirotatsu*; Koyama, Akira*; Yano, Yasuhide
Materia, 47(12), P. 628, 2008/12
no abstracts in English
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.
Kim, S.-W.*; Tanigawa, Hiroyasu; Hirose, Takanori; Koyama, Akira*
Journal of ASTM International (Internet), 5(8), 8 Pages, 2008/09
Depending on the pulse lengths, the operating conditions, and the thermal conductivity, oscillating temperature gradients will cause elastic and elastic-plastic cyclic deformation giving rise to (creep-) fatigue in the structural first wall and blanket components. Small specimen testing technology and related remote-control testing techniques are indispensable for the effective use of the limited volumes of materials test reactor and proposed intense neutron sources. In order to perform an accurate fatigue lifetime assessment using small specimen, the effects of material factors (surface morphology, inclusion, etc.) on low cycle fatigue (LCF) is mandatory. In this work, the LCF properties of F82H IEA heat were examined for three kinds of surface morphology with miniaturized hourglass-type fatigue specimens (SF-1), and the correlation between LCF crack initiation/propagation and distribution of inclusions also revealed by using SF-1 specimen. Fracture surfaces and crack initiation sites were investigated by SEM.
Tanigawa, Hiroyasu; Sakasegawa, Hideo; Ogiwara, Hiroyuki*; Kishimoto, Hirotatsu*; Koyama, Akira*
Journal of Nuclear Materials, 367-370(1), p.132 - 136, 2007/08
Times Cited Count：39 Percentile：91.43(Materials Science, Multidisciplinary)It was previously reported that reduced-activation ferritic/martensitic steels (RAFs), such as F82H-IEA and JLF-1, showed a variety of changes in its mechanical property after neutron irradiation at 573K up to 5dpa, and have possible correlation with precipitation. The effects of irradiation on precipitation were also reported previously. In this study, irradiation effects on precipitation were investigated in detail utilizing ion irradiation in which irradiation condition could be controlled with high accuracy. F82H IEA heat, JLF-1 HFIR heat, and aged F82H-IEA (873K
30k h) were used for experiments. The specimens were irradiated at DuET facility, Inst. of Advanced Energy, Kyoto University up to 10 dpa at 573K with 6.4MeV Fe
ion. Cross sectional TEM thin film specimens of ion irradiated region were made utilizing focused ion beam (FIB) processor with micro-sampling system at JAERI. These thin film specimens were made to contain both irradiated region and non-irradiated region beneath irradiated region. Size distribution and aspect ratio of precipitates were analyzed on each region. It turned out that the finer precipitates were dominant in irradiated region of F82H compared to that in non-irradiated region, but fewer and larger precipitates were dominant in irradiated region of JLF-1. These results confirmed the presence of irradiation effects on precipitate evolution even at 573K, which was observed in neutron irradiated RAFs.
Ando, Masami; Li, M.*; Tanigawa, Hiroyasu; Grossbeck, M. L.*; Kim, S.-W.; Sawai, Tomotsugu; Shiba, Kiyoyuki; Kono, Yutaka*; Koyama, Akira*
Journal of Nuclear Materials, 367-370(1), p.122 - 126, 2007/08
Times Cited Count：15 Percentile：70.27(Materials Science, Multidisciplinary)Irradiation creep behavior of the F82H and several JLF-1 steels have been measured up to 5 dpa, using helium-pressurized creep tubes irradiated in HFIR. These tubes were pressurized with helium to hoop stress levels of 0 to 400 MPa for irradiation temperature. The results of F82H and JLF-1 with 200 MPa hoop stress showed small creep strains (
0.15%) after irradiation. Irradiation creep rate in these steels is linearly dependent on the applied stress less than 200 MPa. However, at higher hoop stress level, the creep rate of them is nonlinear. The creep compliance coefficient for F82H and JLF-1 at 300 
C is very small values. These data contribute to a part of materials database for ITER Test blanket design work.
Ando, Masami; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Jitsukawa, Shiro; Kono, Yutaka*; Koyama, Akira*; Li, M.*; Stoller, R. E.*
Nihon Kinzoku Gakkai-Shi, 71(7), p.559 - 562, 2007/07
Times Cited Count：0 Percentile：0.01(Metallurgy & Metallurgical Engineering)no abstracts in English
Tanigawa, Hiroyasu; Sawahata, Atsushi; Sokolov, M. A.*; Enomoto, Masato*; Klueh, R. L.*; Koyama, Akira*
Materials Transactions, 48(3), p.570 - 573, 2007/03
Times Cited Count：22 Percentile：72.03(Materials Science, Multidisciplinary)The effects of microstructural inhomogeneity of F82H-IEA was investigated focusing on inclusion. It turned out that Ta does not form MX precipitates, but it forms complex Al
O
;Ta(V,Ti)O inclusions, or simple Ta(V)O inclusions. The complex inclusions are rather dominant in the plate obtained from the bottom of the ingot, but not in the plate from the middle of the ingot. SEM observations also revealed that broken complex inclusions tended to be observed at the crack-initiation site. These results suggest that the scatter of toughness values is correlated with this microstructural inhomogeneity, as the MC method assumes the material has a homogeneous microstructure.
Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Hirose, Takanori; Kasada, Ryuta*; Wakai, Eiichi; Jitsukawa, Shiro; Kimura, Akihiko*; Koyama, Akira*
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 6 Pages, 2007/03
The status of research and development of reduced activation martensitic steels (RAMs) in Japan are reviewed and key issues suggested from recent achievements in Japan since the last conference are highlighted, with the aim of the fabrication for the ITER Test Blanket Module (TBM) and application for the DEMO reactor. It was pointed out that international collaboration would be desirable for research on key issues such as precipitate stability under irradiation or Ta effects which are common for all RAMs and require an extensive research effort.
Nakata, Toshiya; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Komazaki, Shinichi*; Fujiwara, Mikio*; Kono, Yutaka*; Koyama, Akira*
Nihon Kinzoku Gakkai-Shi, 71(2), p.239 - 243, 2007/02
Times Cited Count：4 Percentile：33.26(Metallurgy & Metallurgical Engineering)no abstracts in English
Nakata, Toshiya; Komazaki, Shinichi*; Nakajima, Motoki*; Kono, Yutaka*; Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Koyama, Akira*
Nihon Kinzoku Gakkai-Shi, 70(8), p.642 - 645, 2006/08
Times Cited Count：4 Percentile：34.16(Metallurgy & Metallurgical Engineering)no abstracts in English
