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Journal Articles

Development of evaluation method with X-ray tomography for material property of IG-430 graphite for VHTR/HTGR

Sumita, Junya; Shibata, Taiju; Fujita, Ichiro*; Kunimoto, Eiji*; Yamaji, Masatoshi*; Eto, Motokuni*; Konishi, Takashi*; Sawa, Kazuhiro

Nuclear Engineering and Design, 271, p.314 - 317, 2014/05

 Times Cited Count:6 Percentile:48.72(Nuclear Science & Technology)

In this study, in order to develop evaluation method for material properties and to evaluate the irradiation-induced property changes under higher neutron doses for IG-430, the oxidation and densification effects on elastic modulus of IG-430 were investigated. Moreover, the correlation of the microstructure based on the X-ray tomography images and the material properties was discussed. It was shown that the elastic modulus of the densified graphite depends on only the closed pores and it is possible to evaluate the material properties of graphite by using X-ray tomography method. However, it is necessary to take into account of the change in the number and shape of closed pores in the grain to simulate the elastic modulus of the highly oxidized and irradiated materials by the homogenization analysis.

JAEA Reports

Evaluation of oxidation characteristics of fine-grained graphites (IG-110 and IG-430) for very high temperature reactor; Changes in density distribution and compressive strength caused by air-oxidation

Fujita, Ichiro*; Eto, Motokuni*; Osaki, Hirotaka; Shibata, Taiju; Sumita, Junya; Konishi, Takashi; Yamaji, Masatoshi; Kunimoto, Eiji

JAEA-Research 2013-004, 20 Pages, 2013/07

JAEA-Research-2013-004.pdf:2.4MB

Graphite components in HTGR and VHTR may be oxidized by impurities in coolant helium-gas even at normal operation, as well as by air at air-ingress accident. In this study, by air-oxidation test at 520-900$$^{circ}$$C, oxidation characteristics of IG-110 and IG-430 graphites, and associated decrease in compressive strength were examined. The following results were obtained. (1) The activation energy of the air-oxidation for IG-430 is 176 kJ/mol being almost same as for IG-110, though the oxidation rate for IG-430 is less than a half of that for IG-110. (2) There are correlations between density change and decrease in compressive strength. Decrease in strength is the largest in case that the oxidation temperature is lower than 600 $$^{circ}$$C where the homogenous oxidation occurs. (3) In the process of oxidation, amorphous binder regions are predominantly oxidized. It suggests that peeling-off of cokes grains is necessary to be considered for oxidation weight loss, as well as gasification.

Journal Articles

Development of evaluation method with X-ray tomography for material property of IG-430 graphite for VHTR/HTGR

Sumita, Junya; Shibata, Taiju; Fujita, Ichiro*; Kunimoto, Eiji*; Yamaji, Masatoshi*; Eto, Motokuni*; Konishi, Takashi*; Sawa, Kazuhiro

Proceedings of 6th International Topical Meeting on High Temperature Reactor Technology (HTR 2012) (USB Flash Drive), 6 Pages, 2012/10

In this study, in order to develop evaluation method for material properties and to evaluate the irradiation-induced property changes under higher neutron doses for IG-430, the oxidation and densification effects on elastic modulus of IG-430 were investigated. Moreover, the correlation of the microstructure based on the X-ray tomography images and the material properties was discussed. It was shown that the elastic modulus of the densified graphite depends on only the closed pores and it is possible to evaluate the material properties of graphite by using X-ray tomography method. However, it is necessary to take into account of the change in the number and shape of closed pores in the grain to simulate the elastic modulus of the highly oxidized and irradiated materials by the homogenization analysis.

Journal Articles

Research and developments on application of carbon-carbon composite to HTGR/VHTR in Japan

Eto, Motokuni*; Konishi, Takashi*; Shibata, Taiju; Sumita, Junya

IOP Conference Series; Materials Science and Engineering, 18(16), p.162003_1 - 162003_6, 2011/09

 Times Cited Count:1 Percentile:37.28

High Temperature Gas-cooled Reactor (HTGR) and Very High Temperature Reactor (VHTR) are attractive nuclear reactors to obtain high temperature helium gas to the reactor outlet. To enhance the thermal efficiency, the core internals of HTGR/VHTR are subjected to the very severe high temperature condition. The carbon fiber reinforced carbon-carbon composite (C/C composite) is one of the advanced material candidates for the control rod sheath of the reactors because of its excellent thermal resistance and stability in the severe condition. The R&Ds on the C/C composite application to HTGR have been carried out since 1990'. JAEA and Toyo Tanso have been in collaboration with each other in the R&Ds. The development of control rod made of C/C composite is recently focused as one of the important subjects to develop the VHTR in the international R&Ds. The scheme of the development of JAEA is categorized as the following phases; (1) Database establishment, (2) Design and manufacturing of component and (3) Demonstration test by HTTR. At the initial stage of the development in 1990' in JAERI, the feasibility of the control rod using C/C composite was demonstrated by a conceptual design. The phase (2) is planned to be completed within 5 years. This paper presents the review of the development of the control rod made of C/C composite and the recent R&D results.

Journal Articles

Interpolation and Extrapolation method to analyze irradiation-induced dimensional change data of graphite for design of core components in Very High Temperature Reactor (VHTR)

Shibata, Taiju; Kunimoto, Eiji*; Eto, Motokuni*; Shiozawa, Shusaku; Sawa, Kazuhiro; Oku, Tatsuo*; Maruyama, Tadashi*

Journal of Nuclear Science and Technology, 47(7), p.591 - 598, 2010/07

 Times Cited Count:4 Percentile:64.45(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Draft of standard for graphite core components in High Temperature Gas-cooled Reactor

Shibata, Taiju; Eto, Motokuni*; Kunimoto, Eiji*; Shiozawa, Shusaku; Sawa, Kazuhiro; Oku, Tatsuo*; Maruyama, Tadashi*

JAEA-Research 2009-042, 119 Pages, 2010/01

JAEA-Research-2009-042.pdf:26.28MB

For the design of the graphite components in the High Temperature Engineering Test Reactor (HTTR), the graphite structural design code for the HTTR etc. were applied. However, general standard systems for the High Temperature Gas-cooled Reactor (HTGR) have not been established yet. The authors had studied on the technical issues which is necessary for the establishment of a general standard system for the graphite components in the HTGR. The results of the study were documented and discussed at a "Special committee on research on preparation for codes for graphite components in HTGR" at Atomic Energy Society of Japan (AESJ). As a result, "Draft of Standard for Graphite Core Components in High Temperature Gas-cooled Reactor" was established. In this draft standard, the graphite components are classified three categories (A, B and C) in the standpoints of safety functions and possibility of replacement. For the components in the each class, design standard, material and product standards, and in-service inspection and maintenance standard are determined. This draft standard is the first standard in the world which shows the concept of standard for the graphite core components in HTGR.

JAEA Reports

Expansion of irradiation data by interpolation and extrapolation for design of graphite components in high temperature gas-cooled reactor; Evaluation on IG-110 graphite irradiation data for component design

Kunimoto, Eiji; Shibata, Taiju; Shimazaki, Yosuke; Eto, Motokuni*; Shiozawa, Shusaku; Sawa, Kazuhiro; Maruyama, Tadashi*; Oku, Tatsuo*

JAEA-Research 2009-008, 28 Pages, 2009/06

JAEA-Research-2009-008.pdf:4.6MB

The VHTR is being focused and developed internationally. In Japan, the HTTR of the JAEA is in operation, and research and development for the development of commercial HTGRs are carried out. Nuclear graphites are used for core components of the HTGRs and expansion of irradiation data is necessary when enough irradiation data are not established, because the graphite components in the HTGRs are used at severer condition than that in the HTTR. The necessary database can be established by expansion of existing irradiation data with appropriate interpolation and extrapolation methods. This paper shows the reasonable interpolation and extrapolation method for IG-110 graphite which is used for the HTTR and a major candidate for the VHTR. The interpolation and extrapolation method was developed so as to be general by using the irradiation data of the other graphites. As a result, irradiation properties of the IG-110 graphite were successfully expanded to the VHTR condition for the first time and the irradiation properties being necessary for the design could be developed.

Journal Articles

Infrared radiation properties of the carbon-carbon composite and their application to nondestructive detection of its defects

Eto, Motokuni; Ishii, Toshimitsu; Inagaki, Terumi*; Okamoto, Yoshizo*

Carbon, 40(3), p.285 - 294, 2002/03

 Times Cited Count:9 Percentile:59.55

no abstracts in English

Journal Articles

Fatigue behavior on weldment of austenitic stainless steel for ITER vacuum vessel

Nishi, Hiroshi; Eto, Motokuni; Tachibana, Katsumi; Koizumi, Koichi; Nakahira, Masataka; Takahashi, Hiroyuki*

Fusion Engineering and Design, 58-59, p.869 - 873, 2001/11

 Times Cited Count:1 Percentile:86.59

no abstracts in English

Journal Articles

Fracture toughness of HTGR graphites under stress gradient

Ishiyama, Shintaro; Eto, Motokuni

Nippon Genshiryoku Gakkai-Shi, 43(11), p.1159 - 1166, 2001/11

 Times Cited Count:1 Percentile:86.59(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Fatigue strength reduction factor of partial penetration weldments for ITER vacuum vessel

Nishi, Hiroshi; Eto, Motokuni; Tachibana, Katsumi; Nakahira, Masataka

Transactions of 16th International Conference on Structural Mechanics in Reactor Technology (SMiRT-16) (CD-ROM), 8 Pages, 2001/08

Fatigue test of the weldments was performed to investigate their fatigue behavior and the effect of the incomplete penetrations on the fatigue strength. Fatigue crack propagation test of their weld metals was also carried out using CT specimen. By calculating stress intensity factors of the weldments contained the incomplete penetrations and cracks using FEM analysis, the fatigue crack propagation rates of weldments were evaluated and compared those of their weld metals. Fatigue life of the weldments was evaluated based on fracture mechanics to discuss the effect of incomplete penetrations on the fatigue strength. As the results, the incomplete penetration behaved as a crack and most of total fatigue life for the weldment was crack propagation life. The crack propagation rates of weldment were in accordance with those of the weld metals. The fatigue strength of the weldment was considerably lower than that of smoothed specimen. The incomplete penetrations affected greatly the fatigue strength of the weldments even if the depth of incomplete penetrations was small.

Journal Articles

Inertia effect on thermal shock by laser beam shot

Kogawa, Hiroyuki; Futakawa, Masatoshi; Ishikura, Shuichi*; Kikuchi, Kenji; Hino, Ryutaro; Eto, Motokuni

International Journal of Impact Engineering, 25(1), p.17 - 28, 2001/01

 Times Cited Count:3 Percentile:73.69

no abstracts in English

Journal Articles

Dynamic effect on strength in SiC$$_{f}$$/SiC$$_{m}$$ composite

Futakawa, Masatoshi; Tanabe, Yuji*; Wakui, Takashi*; Kogawa, Hiroyuki; Hino, Ryutaro; Eto, Motokuni

International Journal of Impact Engineering, 25(1), p.29 - 40, 2001/01

 Times Cited Count:8 Percentile:54.9

no abstracts in English

Journal Articles

Performance of V-4Cr-4Ti alloy exposed to the JFT-2M tokamak environment

Johnson, W. R.*; Trester, P. W.*; Sengoku, Seio; Ishiyama, Shintaro; Fukaya, Kiyoshi; Eto, Motokuni; Oda, Tomomasa*; Hirohata, Yuko*; Hino, Tomoaki*; Tsai, H.*

Journal of Nuclear Materials, 283-287(Part1), p.622 - 627, 2000/12

 Times Cited Count:2 Percentile:78.72

no abstracts in English

Journal Articles

Development of a small specimen test machine to evaluate irradiation embrittlement of fusion reactor materials

Ishii, Toshimitsu; Omi, Masao; Saito, Junichi; Hoshiya, Taiji; Ooka, Norikazu; Jitsukawa, Shiro; Eto, Motokuni

Journal of Nuclear Materials, 283-287(Part.2), p.1023 - 1027, 2000/12

 Times Cited Count:7 Percentile:49.63

no abstracts in English

Journal Articles

Characterization of non-magnetic Mn-Cr steel as a low induced activation material for vacuum vessels

Saito, Shigeru; Fukaya, Kiyoshi; Ishiyama, Shintaro; Eto, Motokuni; Sato, Ikuo*; Kusuhashi, Mikio*; Hatakeyama, Tsuyoshi*; Takahashi, Heishichiro*; Kikuchi, Mitsuru

Journal of Nuclear Materials, 283-287(Part1), p.593 - 596, 2000/12

 Times Cited Count:1 Percentile:86.68

no abstracts in English

Journal Articles

The Irradiation effect on mechanical properties of brazed structures as divertor target plate for fusion experimental reactors

Ishiyama, Shintaro; Akiba, Masato; Eto, Motokuni

Nippon Genshiryoku Gakkai-Shi, 42(12), p.1334 - 1342, 2000/12

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Fundamental study on in-situ repair technique of armor tiles for fusion experimental reactors

Ishiyama, Shintaro; Baba, Shinichi; Fukaya, Kiyoshi; Eto, Motokuni; Akiba, Masato; Sato, Makoto*; Araki, Toshimitsu*; Yamaguchi, Seiji*; Yamazaki, Seiichiro*

Nippon Genshiryoku Gakkai-Shi, 42(7), p.669 - 677, 2000/07

no abstracts in English

Journal Articles

Mechanical-property evaluation of thin corroded surface layers of ceramic materials by microindentation technique

Futakawa, Masatoshi; Wakui, Takashi*; Ioka, Ikuo; Eto, Motokuni

Journal of the European Ceramic Society, 20(8), p.1135 - 1143, 2000/05

 Times Cited Count:5 Percentile:51.32

no abstracts in English

JAEA Reports

Development of bonding techniques between tungsten and copper alloy for plasma facing components by HIP method, 2; Bonding between tungsten and DS-copper

Saito, Shigeru; Fukaya, Kiyoshi; Ishiyama, Shintaro; Eto, Motokuni; Akiba, Masato

JAERI-Research 2000-006, p.57 - 0, 2000/02

JAERI-Research-2000-006.pdf:20.86MB

no abstracts in English

109 (Records 1-20 displayed on this page)