Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Hirota, Noriaki; Nakano, Hiroko; Fujita, Yoshitaka; Takeuchi, Tomoaki; Tsuchiya, Kunihiko; Demura, Masahiko*; Kobayashi, Yoshinao*
The IV International Scientific Forum "Nuclear Science and Technologies"; AIP Conference Proceedings 3020, p.030007_1 - 030007_6, 2024/01
Dynamic strain aging (DSA) and intergranular stress corrosion cracking (intragranular SCC) occur in high temperature pressurized water simulating a boiling water reactor environment due to changes in dissolved oxygen (DO) content, respectively. In order to clearly understand the difference between these phenomena, the mechanism of their occurrence was summarized. As a result, it was found that DSA due to intragranular cracking occurred in SUS304 stainless steel at low DO 1 ppb, while DSA was suppressed at DO 100 to 8500 ppb due to the formation of oxide films on the surface. On the other hand, when DO was increased to 20000 ppb, the film was peeled from the matrix, O element diffused to the grain boundary of the matrix, resulting in intergranular SCC. These results are indicated that the optimum DO concentration must be adjusted to suppress crack initiation due to DSA and intergranular SCC.
Fujita, Yoshitaka; Hu, X.*; Takeuchi, Tomoaki; Takeda, Ryoma; Fujihara, Yasuyuki*; Yoshinaga, Hisao*; Hori, Junichi*; Suzuki, Tatsuya*; Suematsu, Hisayuki*; Ide, Hiroshi
KURNS Progress Report 2022, P. 110, 2023/07
no abstracts in English
Fujita, Yoshitaka; Seki, Misaki; Ngo, M. C.*; Do, T. M. D.*; Hu, X.*; Yang, Y.*; Takeuchi, Tomoaki; Nakano, Hiroko; Fujihara, Yasuyuki*; Yoshinaga, Hisao*; et al.
KURNS Progress Report 2021, P. 118, 2022/07
no abstracts in English
Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Seki, Misaki; Fujita, Yoshitaka; Fujihara, Yasuyuki*; Zhang, J.*; Yoshinaga, Hisao*; Sano, Tadafumi*; Hori, Junichi*; Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; et al.
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 29(1), p.2 - 9, 2022/06
no abstracts in English
Shibata, Hiroshi; Nakano, Hiroko; Suzuki, Yoshitaka; Otsuka, Noriaki; Nishikata, Kaori; Takeuchi, Tomoaki; Hirota, Noriaki; Tsuchiya, Kunihiko
JAEA-Testing 2017-002, 138 Pages, 2017/12
From the viewpoints of utilization improvement of the Japan Materials Testing Reactor (JMTR), the experimental devices have been established for the out-pile tests in the irradiation technology development building. The devices for the irradiation capsule assembly, material tests and inspections were established at first and experimental data were accumulated before the neutron irradiation tests. On the other hand, after the Great East Japan Earthquake, the repairs and earthquake-resistant measures of the existing devices were carried out. New devices and equipments were also established for the R&D program for power plant safety enhancement of the Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry (METI) and Mo/Tc production development under the Tsukuba International Strategic Zone. This report describes the outline and basic operation manuals of the devices established from 2011 to 2016 and the management points for the safety works in the irradiation technology development building.
Mukai, Yoichi*; Nishida, Akemi; Hamamoto, Takuji*; Sakino, Yoshihiro*; Ikawa, Nozomu*; Takeuchi, Yoshitaka*; Chiba, Fumihiko*; Hori, Yoshiro*
Proceedings of 12th International Conference on Shock and Impact Loads on Structures (SI 2017) (USB Flash Drive), p.329 - 338, 2017/06
AIJ guideline against accidental actions is published as a book, "Introduction to shock-resistant design of buildings". This contains respect to objective and scope, design loads, member design, design criteria, non-structural element, progressive collapse and design examples. The objective of AIJ guideline is to minimize human and property damage in building structures against accidental actions based on the performance-based design. Target buildings for design are offices, apartments, hotels, hospitals, schools and public buildings. Structural systems of the buildings are limited to reinforced concrete and steel frame structures. In this paper, the overview of the AIJ guideline is introduced.
Matsukawa, Yoshitaka*; Takeuchi, Tomoaki; Kakubo, Yuta*; Suzudo, Tomoaki; Watanabe, Hideo*; Abe, Hiroaki*; Toyama, Takeshi*; Nagai, Yasuyoshi*
Acta Materialia, 116, p.104 - 113, 2016/09
Times Cited Count:73 Percentile:95.76(Materials Science, Multidisciplinary)Atom probe tomography (APT) and TEM were combined for identifying the stage at which solute clusters transform into compounds crystallographically distinct from the matrix, in the precipitation of the G-phase (NiSiMn) from ferrite solid solution subjected to isothermal annealing at 673 K. Based on a systematic analysis of solute clusters as a function of annealing time, the nucleation of the G-phase was found to occur via a two-step process. Moreover, the structural change was found to occur via another two-step process. There was a time lag between the end of cluster growth to become a critical size and the start of the structural change. During the incubation period solute enrichment occurred inside the clusters without further size growth, indicating that the nucleation of the G-phase occurs at the critical size with a critical composition. Judging from the results of APT, TEM and the simulation of electron diffraction patterns, the critical composition was estimated to be NiSi(Fe,Cr)Mn.
Tanase, Masakazu*; Fujisaki, Saburo*; Ota, Akio*; Shiina, Takayuki*; Yamabayashi, Hisamichi*; Takeuchi, Nobuhiro*; Tsuchiya, Kunihiko; Kimura, Akihiro; Suzuki, Yoshitaka; Ishida, Takuya; et al.
Radioisotopes, 65(5), p.237 - 245, 2016/05
no abstracts in English
Nishida, Akemi; Ohashi, Yasuhiro*; Obi, Hirotoshi*; Takeuchi, Yoshitaka*; Kano, Toshiya*; Ryuzaki, Hibiki*; Ota, Toshiro*; Kishi, Tokumitsu*; Komuro, Masato*; Nakamura, Naohiro*
Kenchikubutsu No Taishogeki Sekkei No Kangaekata, p.161 - 202, 2015/01
Though design guidelines for earthquake and wind loads are specified for buildings, the guideline for impulsive load as explosion and impact is not specified yet in architectural field. This document corresponds to Chapter 8 of the book titled "Introduction to Shock-Resistant Design of Buildings" which made towards the impact design guideline. Some design examples are presented to illustrate the applicability of the tentative guideline for impulsive loads. Two buildings - a steel frame and a reinforced concrete frame building structures - located at the corner of a crossroads are selected. Dynamic responses and the corresponding damage states are illustrated for the cases of two buildings subjected to impact loads due to road vehicle crashes, internal and external explosions. The idea has been shown in this document are those that can be applied to nuclear facilities.
Nishida, Akemi; Ohashi, Yasuhiro*; Obi, Hirotoshi*; Takeuchi, Yoshitaka*; Takuji, Hamamoto*
Dai-63-Kai Riron Oyo Rikigaku Koenkai Koen Rombunshu (USB Flash Drive), 2 Pages, 2014/09
Though design guidelines for earthquake and wind loads are specified for buildings, the guideline for impulsive load as explosion and impact is not specified yet. Some design examples are presented to illustrate the applicability of the tentative guideline for impulsive loads. Two buildings -a steel frame and a reinforced concrete frame building structures- located at the corner of a crossroads are selected. Dynamic responses and the corresponding damage states are illustrated for the cases of two buildings subjected to impact loads due to road vehicle crashes, internal and external explosions.
Takeuchi, Tomoaki; Kakubo, Yuta*; Matsukawa, Yoshitaka*; Nozawa, Yasuko*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Nishiyama, Yutaka; Katsuyama, Jinya; Yamaguchi, Yoshihito; Onizawa, Kunio; et al.
Journal of Nuclear Materials, 452(1-3), p.235 - 240, 2014/09
Times Cited Count:40 Percentile:95.16(Materials Science, Multidisciplinary)Microstructures and hardness of stainless steel weld overlay cladding of reactor pressure vessels subjected to the thermal aging at 400 C for 100-10,000 h were investigated using atom probe tomography and nanoindentation technique. The Cr concentration fluctuation in the -ferrite phase caused by spinodal decomposition rapidly progressed by the 100 h aging while NiSiMn clusters increased in number density at 2,000 h and coarsened at 10,000 h. The hardness of the -ferrite phase also rapidly increased at the short aging time. The Cr concentration fluctuation and the hardness were in good correlation with the degree of the Cr concentration fluctuation rather than the formation of the NiSiMn clusters. These results strongly suggested that the dominant factor of the hardening of the -ferrite phase by the thermal aging was Cr spinodal decomposition.
Takeuchi, Tomoaki; Kakubo, Yuta*; Matsukawa, Yoshitaka*; Nozawa, Yasuko*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Nishiyama, Yutaka; Katsuyama, Jinya; Yamaguchi, Yoshihito; Onizawa, Kunio
Journal of Nuclear Materials, 449(1-3), p.273 - 276, 2014/06
Times Cited Count:19 Percentile:81.57(Materials Science, Multidisciplinary)Microstructural changes and hardness of stainless steel weld overlay cladding of reactor pressure vessels subjected to the neutron irradiation with a dose of 7.2 10n cm (E 1 MeV) and a flux of 1.1 10n cm s at 290C were investigated by atom probe tomography and with nanoindentation technique. In order to isolate the effect of the irradiation, we compared the results of the measurements of the irradiated sample with that of the aged one at 300C for the time equivalent to the irradiation. The Cr concentration fluctuation was enhanced in the -ferrite phase of the irradiated sample. In addition, the enhancement of the concentration fluctuation of Si, which was not observed in the aged sample, was observed. The hardening at the -ferrite phase was occurred by both the irradiation and the aging. However, the former was more than that expected from the Cr concentration fluctuation, which suggested that the Si concentration fluctuation and irradiation-induced defects were possible origins of the additional hardening.
Takeuchi, Tomoaki; Kakubo, Yuta*; Matsukawa, Yoshitaka*; Nozawa, Yasuko*; Nagai, Yasuyoshi*; Nishiyama, Yutaka; Katsuyama, Jinya; Onizawa, Kunio; Suzuki, Masahide
Journal of Nuclear Materials, 443(1-3), p.266 - 273, 2013/11
Times Cited Count:16 Percentile:76.68(Materials Science, Multidisciplinary)Investigation on irradiation effects of weld-overlay claddings is necessary for safety assessment of reactor pressure vessels. We investigated microstructural changes in the cladding, which was composed of about 90% austenite and 10% -ferrite phases, subjected to the neutron irradiation to 7.210 n/cm at 290C, by 3D atom probe tomography technique. In the ferrite phase, the amplitude of the Cr and Si concentration fluctuation was increased by the irradiation and Ni and Mn concentration fluctuations were newly occurred. In the austenite phase, '(NiSi) -like clusters were formed. In contrast, the results of our previous work on the cladding subjected to thermal aging showed the amplitude of the Cr fluctuation was significantly increased and G (Ni-Si-Mn) phase was formed in the ferrite phase. Moreover, no changes were observed in the austenite by the aging.
Nishida, Akemi; Ohashi, Yasuhiro*; Obi, Hirotoshi*; Takeuchi, Yoshitaka*; Takuji, Hamamoto*
Proceedings of 9th International Conference on Shock & Impact Loads on Structures (CD-ROM), 10 Pages, 2011/11
Some design examples are presented to illustrate the applicability of the tentative AIJ guideline to a selection of buildings. Two buildings, a reinforced concrete and a steel frame building structure, located at the corner of a crossroads were selected. Two accident scenarios are considered: road vehicle crashes caused by automobiles and dump trucks and internal gas explosion. Application examples of road vehicle crashes at the first floor of the selected buildings and internal gas explosion are shown in this paper. As an example of non-structural member, this study also presents information on glass velocity and dispersion when loaded by an internal gas explosion.
Tobita, Kenji; Tani, Keiji; Kusama, Yoshinori; Nishitani, Takeo; Ikeda, Yoshitaka; Neyatani, Yuzuru; S.V.Konovalov*; Kikuchi, Mitsuru; Koide, Yoshihiko; Hamamatsu, Kiyotaka; et al.
Nuclear Fusion, 35(12), p.1585 - 1591, 1995/00
Times Cited Count:68 Percentile:88.29(Physics, Fluids & Plasmas)no abstracts in English
Kondoh, Takashi; Ide, Shunsuke; Imai, Tsuyoshi; Ushigusa, Kenkichi; Ikeda, Yoshitaka; Seki, Masami; Takeuchi, Hiroshi
Proc. of the 1992 Int. Conf. on Plasma Physics,Vol. 16C Part 2, p.II969 - II972, 1992/00
no abstracts in English
Seki, Masami; Ikeda, Yoshitaka; Imai, Tsuyoshi; Ushigusa, Kenkichi; Naito, Osamu; Ide, Shunsuke; Kondoh, Takashi; Nemoto, Masahiro; Takeuchi, Hiroshi; Suganuma, Kazuaki; et al.
Proc. of the 19th European Conf. on Controlled Fusion and Plasma Physics, p.985 - 988, 1992/00
no abstracts in English
Nemoto, Masahiro; Ushigusa, Kenkichi; Imai, Tsuyoshi; Ikeda, Yoshitaka; Naito, Osamu; Kusama, Yoshinori; Tobita, Kenji; Takeuchi, Hiroshi; JT-60 Team
Physical Review Letters, 67(1), p.70 - 73, 1991/07
Times Cited Count:14 Percentile:70.08(Physics, Multidisciplinary)no abstracts in English
Takeuchi, Tomoaki; Nishiyama, Yutaka; Katsuyama, Jinya; Onizawa, Kunio; Matsukawa, Yoshitaka*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Kameda, Jun*
no journal, ,
Microstructure evolution on stainless overlay cladding of reactor pressure vessel was quantitatively investigated by means of three-dimensional local electrode atom probe (3DAP) in nano-scale. The cladding material was neutron-irradiated up to 710n/cm (E 1 MeV)at JMTR. In ferrite phases of cladding material, a 12% of Cr concentration fluctuation, which was arisen through a spinodal decomposition, observed before the irradiation was progressed to 20% after the irradiation while the wave length of the fluctuation was almost not changed about 8-10 nm before and after the irradiation. In addition, Ni, Si and Mn concentration fluctuations were also observed. Correlation between Cr concentration fluctuation and hardness, other elements concentration fluctuation and differences from the thermal aging will be reported in presentation.