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-ray analysisKinoshita, Norikazu*; Noto, Takuma*; Nakajima, Hitoshi*; Kosako, Kazuaki*; Kato, Takahiro*; Kuroiwa, Yoichi*; Kurabe, Misako*; Sasaki, Yuki*; Torii, Kazuyuki*; Maeda, Makoto; et al.
Journal of Radioanalytical and Nuclear Chemistry, 332(2), p.479 - 486, 2023/02
Kim, B. K.*; Tan, L.*; Sakasegawa, Hideo; Parish, C. M.*; Zhong, W.*; Tanigawa, Hiroyasu*; Kato, Yutai*
Journal of Nuclear Materials, 545, p.152634_1 - 152634_12, 2021/03
Times Cited Count：1 Percentile：16.35(Materials Science, Multidisciplinary)Hirose, Takanori; Nozawa, Takashi; Stoller, R. E.*; Hamaguchi, Dai; Sakasegawa, Hideo; Tanigawa, Hisashi; Tanigawa, Hiroyasu; Enoeda, Mikio; Kato, Yutai*; Snead, L. L.*
Fusion Engineering and Design, 89(7-8), p.1595 - 1599, 2014/10
Times Cited Count：47 Percentile：96.65(Nuclear Science & Technology)The material properties, focusing on the properties used for design analysis were re-assessed and newly investigated for various heats including F82H-IEA. Moreover, irradiation effects on those properties were studied in this work. As for thermal properties, thermal conductivity that has significant impacts on the thermo-hydraulic properties of the blanket was investigated on several heats of F82H including F82H-IEA. According to the measurements, the thermal conductivity falls in the range 28.3
1.1 W/m/K at 293 K. Although this is comparable with that of the other ferritic/martensitic steels, it is 20% lower than the published value for F82H-IEA. The re-assessment on the published value revealed that the thermal diffusivity was over-estimated. As for irradiation effects on the physical properties, electric resistivity was measured after irradiation up to 6 dpa at 573 K and 673 K. The reduction of resistivity in F82H and its welds were 3% and 6%, respectively.
Takizawa, Kentaro*; Kakehashi, Kazuyuki*; Fukuda, Toshiaki*; Kida, Toru*; Sawa, Kazuhiro; Sumita, Junya; Kato, Yutai*; Snead, L. L.*
Ceramic Materials for Energy Applications; Ceramic Engineering and Science Proceedings, Vol.32, No.9, p.13 - 19, 2011/11
Fine-grained isotropic graphite shows high strength making it a promising material for the graphite component of High Temperature Gas-cooled Reactor (HTGR) and Very High Temperature Reactor (VHTR). Service life of the graphite component is determined primarily by the residual strength after neutron irradiation in the reactor core. It is expected that development of a new nuclear grade graphite possessing higher strength will contribute toward added design margins and an extension of the service life of components, which likely improve the reactor economy very significantly. Tokai Carbon Co. LTD. has started the development of nuclear grade graphite for the graphite component of VHTR. G347S and G458S grades are fine-grained isotropic graphites having high tensile strength greater than 30 MPa. It is planned to carry out the neutron irradiation tests using High Flux Isotope Reactor at Oak Ridge National Laboratory up to the neutron fluence of 30 dpa and the irradiation temperatures of 300-900
C. The dimensional changes, elastic modulus, coefficient of thermal expansion, etc., will be studied. It is also planned to evaluate the non-irradiated mechanical/thermal properties and the irradiation effects in collaboration with Japan Atomic Energy Agency. This paper introduces our technical R&D plan for G347S and G458S. The initial results of the properties and the irradiation test plan are also shown.
Hirose, Takanori; Okubo, Nariaki; Tanigawa, Hiroyasu; Kato, Yutai*; Clark, A. M.*; McDuffee, J. L.*; Heatherly, D. W.*; Stoller, R. E.*
DOE/ER-0313/49, p.94 - 99, 2010/12
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.
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：47 Percentile：82.48(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.
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：92.89(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.
Tanigawa, Hiroyasu; Hirose, Takanori; Ando, Masami; Jitsukawa, Shiro; Kato, Yudai*; Koyama, Akira*
Journal of Nuclear Materials, 307-311(Part1), p.293 - 298, 2002/12
Times Cited Count：9 Percentile：51.46(Materials Science, Multidisciplinary)It has been a key issue to get the mechanical understanding of fracture process on microstructure basis, especially on neutron-irradiated materials, but not yet to be understood well enough as for the difficulty of making transmission electron microscope (TEM) thin film sample from mechanical-tested specimen. To solve this technical problem, the focused ion beam (FIB) micro-sampling system was installed to the Research Hot Laboratory of Japan Atomic Research Institute (JAERI), Japan. This system makes it possible to fabricate the TEM specimens from the critical points of mechanical-tested radioactive specimens, such as the crack initiation points of fatigue fracture on neutron irradiated specimen. In this paper, the microstructure of mechanical-tested specimen of Reduced Activation Ferritic/martensitic steels, RAFs are investigated focusing on the helium effects to fatigue fracture.
Ando, Masami; Tanigawa, Hiroyasu; Jitsukawa, Shiro; Sawai, Tomotsugu; Kato, Yudai*; Koyama, Akira*; Nakamura, Kazuyuki; Takeuchi, Hiroshi
Journal of Nuclear Materials, 307-311(Part1), p.260 - 265, 2002/12
Times Cited Count：39 Percentile：90.08(Materials Science, Multidisciplinary)no abstracts in English
Igawa, Naoki; Taguchi, Tomitsugu; Snead, L. L.*; Kato, Yudai*; Jitsukawa, Shiro; Koyama, Akira*; McLaughlin, J. C.*
Journal of Nuclear Materials, 307-311(Part2), p.1205 - 1209, 2002/12
Times Cited Count：16 Percentile：69.83(Materials Science, Multidisciplinary)no abstracts in English
Taguchi, Tomitsugu; Igawa, Naoki; Jitsukawa, Shiro; Nozawa, Takashi*; Kato, Yudai*; Koyama, Akira*; Snead, L. L.*; McLaughlin, J. C.*
Advanced SiC/SiC Ceramic Composites: Developments and Applications in Energy Systems; Ceramic Transactions Vol. 144, p.69 - 76, 2002/00
Process optimization for Forced-thermal gradient Chemical Vapor Infiltration (FCVI) fabrication of 75 mm diameter size SiC composites with advanced SiC fibers; Hi-Nicalon Type S and Tyranno SA, was carried out. The SiC/SiC composites fabricated by FCVI exhibited significant reduction in porosity (15.1%) and more uniform pore distribution by decreasing the MTS and H
gases flow rates in the latter part of the FCVI process. The tensile strength of the both composites using Hi-Nicalon Type S or Tyranno SA fibers was slightly increased with increased thickness of carbon interphase in the range of 75-300 nm. In order to perform the comparative testing required to directly compare the thermomechanical property changes following neutron irradiation, larger composites with uniform microstructural property are required. From the results of process optimization for fabrication of 75 mm diameter size FCVI SiC/SiC composites, the definitive purpose in this study is the fabrication of the 300 mm diameter size SiC/SiC composite with the uniform microstructural properties.
Tanigawa, Hiroyasu; Ando, Masami; Kato, Yudai*; Hirose, Takanori*; Sakasegawa, Hideo*; Jitsukawa, Shiro; Koyama, Akira*; Iwai, Takeo*
Journal of Nuclear Materials, 297(3), p.279 - 284, 2001/09
Times Cited Count：34 Percentile：89.95(Materials Science, Multidisciplinary)no abstracts in English
Tanigawa, Hiroyasu; Jitsukawa, Shiro; Hishinuma, Akimichi; Ando, Masami*; Kato, Yudai*; Koyama, Akira*; Iwai, Takeo*
Journal of Nuclear Materials, 283-287(Part.1), p.470 - 473, 2000/12
Times Cited Count：21 Percentile：77.56(Materials Science, Multidisciplinary)no abstracts in English
Koyama, Akira*; Donomae, Takako; Kato, Yutai
JNC TY9400 2000-017, 65 Pages, 2000/03
JNC-TY9400-2000-017.pdf:9.69MB
no abstracts in English
Yamada, Reiji; Snead, L. L.*; Kato, Yudai*
Proceedings of 4th International Energy Agency Workshop on SiCf/SiC Ceramic Composites for Fusion Structural Application, p.175 - 180, 2000/00
no abstracts in English
Hirano, Koichiro; Nomura, Masahiro; Yamazaki, Yoshio; *; *; *; *
JNC TN9400 99-040, 52 Pages, 1999/05
The development of a high power CW electron linear accelerator was started in 1989 to study the feasibility of nuclear waste transmutation. The accelerator (10MeV, 100mA peak current, 4 ms pulse width, 50 Hz repetition) is dedicated machine for development of the high current acceleration technology in future need. It is necessary to develop the system which controls high power RF in order to stably accelerate the high current beam. Then, We have developed the interlock system for protecting accelerating tube from high current beam in time of trouble of high current beam and high power RF. We have succeeded in the development of the system so as to be able to choose interlock elements corresponding to the operating condition. Using the beam of the low electric power, the synthetic interlock system was tested. The beam was cut off at 3.5
sec, after the interlock operated.
Emoto, Takashi; Kato, Yuko*; Hirano, Koichiro; Ishikawa, Y.*; Takei, Hayanori; Nomura, Masahiro; Tani, Satoshi
PNC TN9410 98-060, 45 Pages, 1998/06
Design and construction of a high power cw (Continuous Wave) electron linac for studying feasibility of nuclear waste transmutation was started in 1989 at PNC. The PNC accelerator (10Mev, 20mA average current, 4 ms pulse width, 50 Hz repetition) is dedicated machine for development of the high current acceleration technology in future need. The computer control system is responsible for accelerator control and supporting the experiment for high power operation. The feature of the system is the measurements of accelerator status simultaneously and modularity of software and hardware for easily implemented for modification or expansion. The high speed network (SCRAMNet
15MB/s), Ethernet, and front end processors (Digital Signal Processor) were employed for the high speed data taking and control. The system was designed to be standard modules and software implemented man machine interface. Due to graphical-user-interface and object-oriented-programming, the software development environment is effortless programming and maintenance.
Nozawa, Takashi; Kato, Yutai*; Snead, L. L.*
no journal, ,
This study aims to identify the effect of neutron irradiation on the fiber/matrix interface of advanced SiC/SiC composites. A single fiber push-out test was applied to evaluate the shear properties at the interface. The results indicate that the interfacial shear strength depends significantly on the irradiation temperature and neutron dose up to 7.7 dpa at 
1080C. It is worth noting that no major deterioration of the bulk strength of the composites is expected by the slight decrease of interfacial shear properties. This paper will report the general guideline to design irradiation resistant fiber/matrix interface and critical issues for further development will be discussed.
Nozawa, Takashi; Kato, Yutai*; Kishimoto, Hirotatsu*; Koyama, Akira*
no journal, ,
One of the advantages for highly-crystalline and stoichiometric silicon carbide (SiC) composites (advanced SiC/SiC) is improved stability of chemical, physical and mechanical properties at high-temperatures. Besides, it has been revealed that significant contribution from the optimized fiber/matrix (F/M) interface enables to give good quasi-ductility beyond matrix cracking. Though the importance of the F/M interfacial role is recognized, understanding the mechanism of crack propagation is insufficient. Meanwhile, the existing test methods to determine fracture resistance of composites, i.e., a critical energy required to propagate a crack, are not fully established because of very limited considerations on the influence of irreversible energies emerged by interaction at the F/M interface and microcrack forming. This study aims to develop a fracture resistance test methodology and to quantify the crack resistance of advanced SiC/SiC composites.
