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Saijo, Tomoaki; Shimazaki, Yosuke; Ishihara, Masahiro
JAEA-Technology 2025-010, 126 Pages, 2025/12
JAEA-Technology-2025-010.pdf:12.52MB
During the operation of the High Temperature Engineering Test Reactor (HTTR), thermal stress is generated in the graphite components. In addition, graphite exhibits dimensional shrinkage and creep deformation under neutron irradiation. As a result, residual stress remains in the graphite components during reactor shutdown. Therefore, in the design of the HTTR core graphite structures, stress analyses of the graphite components have previously been performed using the finite element analysis code VIENUS. In the HTTR, the graphite components are exposed to a wide range of temperature, from approximately 400
C to 1200C, depending on their location. Consequently, irradiation-induced behaviors such as material property changes and irradiation shrinkage vary among the graphite components. On the other hand, since VIENUS code evaluates stress based on thermal fluid and heat conduction analysis results, it is not suitable for parametric studies. In this study, the influence of irradiation behavior on the stress behavior of graphite components in the wide temperature range (400C to 1200C) was analyzed using simplified viscoelastic evaluation model, consisting of two beam elements, to conduct efficient parametric studies. Operational stress exhibits two distinct patterns depending on whether the irradiation temperature is below or above 800C, due to irradiation shrinkage. Residual stress approaches the thermal stress, preventing excessive increase even when irradiation shrinkage is large. Moreover good agreement in stress behavior trends was observed between the stress analysis results by the simplified viscoelastic evaluation model and VIENUS code. These results indicate that the simplified viscoelastic evaluation model is beneficial in simulating stress behavior.
Baba, Shinichi; Nemoto, Makoto*; Sozawa, Shizuo; Yamaji, Masatoshi*; Ishihara, Masahiro; Sawa, Kazuhiro
JAERI-Tech 2005-055, 157 Pages, 2005/09
JAERI-Tech-2005-055.pdf:19.06MB
The Japan Atomic Energy Research Institute (JAERI) has been carrying out the research on radiation damage mechanism of heat-resistant ceramics composite materials, as one of the subjects of the innovative basic research on high temperature engineering using the High Temperature Engineering Test Reactor (HTTR). A series of preliminary irradiation tests is being made using the Japan Materials Testing Reactor (JMTR). The present report describes results of post-irradiation examinations so far on specimens irradiated in the second and third capsule, designated 98M-41A and 99M-30A, to fast neutron fluences of 1.0
10
m
(E
1MeV) at temperatures of 973K-1173K and 1273K-1473K. The PIE were conducted as the fundamental statistics index of the diametral dimensions for irradiated specimen, irradiation induced dimensional change rate and thermal expansion rate.
Oku, Tatsuo*; Ishihara, Masahiro
Nuclear Engineering and Design, 227(2), p.209 - 217, 2004/01
Times Cited Count：38 Percentile：89.07(Nuclear Science & Technology)The lifetime of graphite material and/or components has been discussed individually from different concepts, and sometimes gives confusion to material researchers as well as designers. The lifetime of graphite materials is determined based on the dimensional changes due to neutron irradiation, at which they return to their original dimensions after initially contracting. On the other hand, the lifetime of graphite components for HTGRs is defined based on a margin of the specified minimum ultimate strengths of the graphite to the stresses induced in the graphite components. As an example, the stresses induced in the graphite block for the HTTR were, then, compared with the limited stress value determined from the specified minimum ultimate strength, and the lifetime of the graphite component was evaluated and compared with that defined as dimensional changes. As a result, it was found that the lifetime of graphite components for HTGRs should be determined as the shorter one in the two lifetimes defined by the stress-strength relationship and by the dimensional changes.
Baba, Shinichi; Ishihara, Masahiro; Sozawa, Shizuo; Sekino, Hajime
JAERI-Data/Code 2003-003, 394 Pages, 2003/03
JAERI-Data-Code-2003-003.pdf:13.63MB
The research on the radiation damage mechanism of heat resistant ceramic composite materials is one of the research subjects of the innovative basic research in the field of high temperature engineering, using the High Temperature engineering Test Reactor (HTTR). Three series of irradiation tests on the heat resistant ceramic composite materials, first to third irradiation test program, were carried out using the Japan Material Testing Reactor (JMTR). This is a summary report on the the first irradiation test program; irradiation induced dimensional change, thermal expansion coefficient, X-ray diffraction and 
-ray spectrum are reported.
Arai, Kenji*; Kurita, Tomohisa*; Nakamaru, Mikihide*; Fujiki, Yasunobu*; Nakamura, Hideo; Kondo, Masaya; Obata, Hiroyuki*; Shimada, Rumi*; Yamaguchi, Ken*
Proceedings of 10th International Conference on Nuclear Engineering (ICONE 10) (CD-ROM), 7 Pages, 2002/00
no abstracts in English
Eto, Motokuni; Ishiyama, Shintaro; ; Fukaya, Kiyoshi;
Journal of Nuclear Materials, 212-215, p.1223 - 1227, 1994/00
Times Cited Count：18 Percentile：80.49(Materials Science, Multidisciplinary)no abstracts in English
Iyoku, Tatsuo; Ishihara, Masahiro;
Journal of Nuclear Science and Technology, 28(10), p.921 - 931, 1991/10
no abstracts in English
Hayashi, Kimio; ; ; Shiozawa, Shusaku; Sawa, Kazuhiro; ; Kikuchi, Teruo; Fukuda, Kosaku
JAERI-M 91-111, 38 Pages, 1991/07
no abstracts in English
