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Sumita, Junya; Shibata, Taiju; Osaki, Hiroki*; Eto, Motokuni*; Konishi, Takashi*
no journal, ,
Graphite materials are used for the in-core components of High Temperature Gas-cooled Reactor (HTGR). The HTGR is particularly attractive due to its passive and inherent safety features. The Very High Temperature Reactor (VHTR) is one of the most promising candidates as the Generation-IV nuclear reactor systems. IG-110 graphite having high strength and resistance to oxidation is used in the HTTR of JAEA and HTR-PM in China. IG-110 graphite is also a major candidate for the in-core graphite components of VHTR, too. IG-430 graphite having the higher strength and resistance to oxidation than IG-110 is an advanced candidate for the VHTR. In this study, the elastic modulus and coefficient of thermal expansion of these graphites were measured and correlation of compressive strength and microstructure was evaluated. Moreover, the densification effects on the material properties were discussed from the standpoint of microstructure using X-ray tomography method.
Sumita, Junya; Shibata, Taiju; Tachibana, Yukio; Kuroda, Masatoshi*
no journal, ,
An application of higher heat-resistant ceramic material to the control rod of VHTR is required for the VHTR development, since the core components of the VHTR will be subject to the severer condition than that of the HTGR. The carbon fiber reinforced carbon composite (C/C composite) is one of the major candidate materials as substitute for the metallic materials which has been generally used for the control rod of nuclear reactors. In this study, tension-compression fatigue tests have been carried out by using two types of the 2D-C/C composite (made by Toyo Tanso and Tokai Carbon) to obtain the design data for VHTR. The microstructure of the ruptured specimens was also observed to clarify the fracture mechanism of the 2D-C/C composite. As a result, the fatigue properties were almost the same between the two types of the 2D-composite. On the other hand, the fracture mechanism was different between them depending on their matrix property.