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Osaki, Hirotaka; Shimazaki, Yosuke; Sumita, Junya; Shibata, Taiju; Konishi, Takashi; Ishihara, Masahiro
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 8 Pages, 2015/05
For the design on the VHTR graphite components, it is desirable to employ graphite material with higher strength. IG-430 graphite has been developed as an advanced candidate for VHTR. However, the new developed IG-430 does not have enough databases for the design of HTGR. In this paper, the compressive strength (Cs) of IG-430, one of important strengths for design data, is statistically evaluated. The component reliability is evaluated based on the safety factors defined by the graphite design code, and the applicability as the VHTR graphite material is discussed. It was found that IG-430 has higher strength (about 11%) and lower standard deviation (about 27%) than IG-110 which is one of traditional graphites used for HTGR, because the crack in IG-430 would not easy to propagate rather than IG-110. Since fracture probability for IG-430 is low, the higher reliability of core-component will be achieved using IG-430. It is expected that IG-430 is applicable for VHTR graphite material.
Sumita, Junya; Shibata, Taiju; Sakaba, Nariaki; Osaki, Hiroki*; Kato, Hideki*; Fujitsuka, Kunihiro*; Muto, Takenori*; Gizatulin, S.*; Shaimerdenov, A.*; Dyussambayev, D.*; et al.
Proceedings of 7th International Topical Meeting on High Temperature Reactor Technology (HTR 2014) (USB Flash Drive), 7 Pages, 2014/10
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. In the case of air ingress accident in HTGR, SiO
protective layer is formed on the surface of SiC layer in TRISO CFP and oxidation of SiC does not proceed and fission products are retained inside the fuel particle. A new safety concept for the HTGR, called Naturally Safe HTGR, has been recently proposed. To enhance the safety of Naturally Safe HTGR ultimately, it is expected that oxidation-resistant graphite is used for graphite components to prevent the TRISO CFPs and fuel compacts from failure. SiC coating is one of candidate methods for oxidation-resistant graphite. JAEA and four graphite companies launched R&Ds to develop the oxidation-resistant graphite and the International Science and Technology Center(ISTC) partner project with JAEA and INP was launched to investigate the irradiation effects on the oxidation-resistant graphite. To determine grades of the oxidation-resistant graphite which will be adopted as irradiation test, a preliminary oxidation test was carried out. This paper described the results of the preliminary oxidation test, the plan of out-of-pile test, irradiation test and post-irradiation test(PIE)of the oxidation-resistant graphite.
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
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 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.
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.
Shibata, Taiju; Sumita, Junya; Ueta, Shohei; Osaki, Hirotaka; Kunimoto, Eiji; Eto, Motokuni*; Konishi, Takashi
no journal, ,
no abstracts in English
Shibata, Taiju; Sumita, Junya; Nagata, Hiroshi; Saito, Takashi; Tsuchiya, Kunihiko; Sakaba, Nariaki; Osaki, Hiroki*; Kato, Hideki*; Fujitsuka, Kunihiro*; Muto, Takenori*; et al.
no journal, ,
no abstracts in English
Osaki, Hirotaka; Konishi, Takashi*; Eto, Motokuni*; Shibata, Taiju; Sumita, Junya
no journal, ,
no abstracts in English
Shimazaki, Yosuke; Shinohara, Masanori; Ono, Masato; Tochio, Daisuke; Osaki, Hirotaka; Sawa, Kazuhiro
no journal, ,
no abstracts in English
Osaki, Hiroki*; Sumita, Junya; Shibata, Taiju; Konishi, Takashi*
no journal, ,
Boron-doped graphite is one of candidate materials for oxidation-resistant graphite. It was reported that BO
, which was generated by oxidation of B
C, prevented boron-doped graphite from oxidation. However, to apply boron-doped graphite to core support graphite structure of HTGR, it is necessary to measure the mechanical and thermal property of oxidized boron-doped graphite. This study reports results of oxidation test, bending strength test and surface observation using GB-210 fabricated by Toyo Tanso Co., Ltd. in order to measure the bending strength of oxidized boron-doped graphite.
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 BO, which was generated by oxidation of BC, 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.