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Sumita, Junya; Osaki, Hiroki*; Kunimoto, Eiji*; Yamaji, Masatoshi*; Konishi, Takashi*
no journal, ,
Graphite materials are used for the in-core components of High Temperature Gas-cooled Reactor (HTGR) which is a graphite-moderated and helium gas-cooled reactor. The HTGR is particularly attractive due to capability of producing high temperature helium gas, and its passive and inherent safety features. It is required for core support graphite structure, which support the core, to have oxidation resistance in the case of air ingress accident in order to maintain the core arrangement and cool the core from a viewpoint of ensuring high safety of HTGR. Boron-doped graphite is one of candidate materials for oxidation-resistant graphite. It was reported that B
O
, which was generated by oxidation of B
C, prevented boron-doped graphite from oxidation. To apply boron-doped graphite to core support graphite structure of HTGR, it is necessary to understand oxidation mechanism of boron-doped graphite. This study reports evaluation results of oxidation mechanism of boron-doped graphite on the basis of oxidation test, bending strength test and surface observation.
Kunimoto, Eiji*; Sumita, Junya; Osaki, Takashi*; Osaki, Hiroki*; Yamaji, Masatoshi*; Konishi, Takashi*
no journal, ,
Graphite materials are used for the in-core components of High Temperature Gas-cooled Reactor (HTGR) which is a graphite-moderated and helium gas-cooled reactor. The major features of the HTGR are that the HTGR can take out the high-temperature helium gas at the reactor outlet and has inherent safety characteristics. 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-10 in China. Moreover, IG-110 graphite provides highly consistent quality and long-term stable supply. IG-110 graphite is a major candidate for the in-core graphite components of VHTR. IG-430 graphite having the higher strength and resistance to oxidation than IG-110 is an advanced candidate for the VHTR. However, a new material of IG-430 does not have enough databases for the design of HTGR. Therefore, preparation of the necessary database for the design, mechanical and thermal properties, irradiation effect on them, is underway. In this study, the tensile strength, compressive strength and fatigue strength of IG-430 were statistically evaluated and the applicability of IG-430 as HTGR graphite materials was discussed. Moreover, the Su value of tensile and compressive strength of IG-430 was evaluated and compared to that of IG-110. It was found that IG-430 has excellent properties.
Fujitsuka, Kunihiro*; Kondo, Akira*; Sumita, Junya; Sakaba, Nariaki; Fukuda, Toshiaki*
no journal, ,
High Temperature Gas-cooled Reactor (HTGR) including High Temperature engineering Test Reactor (HTTR) constructed by Japan Atomic Energy Agency (JAEA) and Very High Temperature Reactor (VHTR) are able to supply high temperature helium gas at the reactor outlet, and possess inherent safety. Fine-Grained isotropic graphite with high strength is used for the in-components of HTGR. In the case of severe accident, for example air ingress accident, it is desirable that oxidation-resistant graphite is used for the in-component of HTGR. One of the effective methods for oxidation-resistant property on graphite is to coat the surface with ceramics, such as SiC, which forms SiO layer when it oxidizes. This method is one of the general industrial methods called chemical vapor deposition (CVD). Tokai Carbon Co., Ltd. (Tokai carbon) and JAEA launched R&Ds to develop the oxidation-resistant graphite. Tokai Carbon manufactured the oxidation-resistant graphite coated with SiC by CVD etc., and oxidation test and observation of surface condition before and after oxidation were carried out. Moreover, irradiation test using WWR-K research reactor in Institute of Nuclear Physics of the Republic of Kazakhstan (INP) was carried out and post-irradiation examination will begin soon. This presentation shows the oxidation behaviour of the oxidation-resistant graphite according to weight change of specimens, and the surface condition of the specimen according to surface and cross section observation of specimens before and after oxidation.