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Journal Articles

Impact of hydrided and non-hydrided materials near transistors on neutron-induced single event upsets

Abe, Shinichiro; Sato, Tatsuhiko; Kuroda, Junya*; Manabe, Seiya*; Watanabe, Yukinobu*; Liao, W.*; Ito, Kojiro*; Hashimoto, Masanori*; Harada, Masahide; Oikawa, Kenichi; et al.

Proceedings of IEEE International Reliability Physics Symposium (IRPS 2020) (Internet), 6 Pages, 2020/04

Single event upsets (SEUs) caused by neutrons have been recognized as a serious reliability problem for microelectronic devices on the ground level. In our previous work, it was found that hydride placed in front of the memory chip has considerably impact on SEU cross sections because H ions generated via elastic scattering of neutrons with hydrogen atoms are only emitted in a forward direction. In this study, the effect of components neighboring transistors on neutron-induced SEUs was investigated for 65-nm bulk SRAMs by using PHITS. It was found that the shape of the SEU cross section around few MeV comes from the thickness and the position of components placed in front of transistors when that components do not contains hydrogen atoms. By considering components adjoin memory cells in the test board used in the simulation, measured data at J-PARC BL10 were reproduced well. In addition, it was found that the effect of components neighboring transistors on neutron-induced SERs does not negligible in terrestrial environment.

Journal Articles

Evaluation of fracture toughness of fine-grained isotropic graphites for HTGR

Yamada, Teruaki*; Matsushima, Yuki*; Kuroda, Masatoshi*; Sumita, Junya; Shibata, Taiju; Fujita, Ichiro*; Sawa, Kazuhiro

Nuclear Engineering and Design, 271, p.323 - 326, 2014/05

 Times Cited Count:5 Percentile:43.74(Nuclear Science & Technology)

In order to investigate the effects of the experimental methodology and the notch angle on the fracture toughness of the fine-grained isotropic nuclear graphites IG-110 and IG-430, the three-point-bending test, which has been recently proposed as the methodology to evaluate the fracture toughness of graphite for high temperature gas-cooled reactors (HTGRs), was performed using two types of the specimens with different notch angles. The results obtained in this study could be summarized as follows: (1) The values of the fracture toughness of IG-110 and IG-430 measured in this study were 0.890 MPa m$$^{1/2}$$ and 1.031 MPa m$$^{1/2}$$, respectively. It was also found that the value of the fracture toughness of IG-110 was nearly equal to or smaller than the values obtained by the other method reported previously. (2) The values of the fracture toughness of the fine-grained isotropic graphites were not affected between the notch angles introduced by the incisive razor blade. (3) The ratio of the tensile strengths of IG-110 and IG-430 was estimated from Griffith Theory using the experimental data obtained in this study. The estimated strength ratio was in good agreement with the strength ratio obtained from the supplier's data.

Journal Articles

Evaluation of fracture toughness of fine-grained isotropic graphites for HTGR

Yamada, Teruaki*; Matsushima, Yuki*; Kuroda, Masatoshi*; Sumita, Junya; Shibata, Taiju; Fujita, Ichiro*; Sawa, Kazuhiro

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

In order to investigate the effects of the experimental methodology and the notch angle on the fracture toughness of the fine-grained isotropic nuclear graphites IG-110 and IG-430, the three-point-bending test, which has been recently proposed as the methodology to evaluate the fracture toughness of graphite for high temperature gas-cooled reactors (HTGRs), was performed using two types of the specimens with different notch angles. The results obtained in this study could be summarized as follows: (1) The values of the fracture toughness of IG-110 and IG-430 measured in this study were 0.890 (MPam$$^{1/2}$$) and 1.031 (MPam$$^{1/2}$$), respectively. It was also found that the value of the fracture toughness of IG-110 was nearly equal to or smaller than the values obtained by the other method reported previously. (2) The values of the fracture toughness of the fine-grained isotropic graphites were not affected between the notch angles introduced by the incisive razor blade. (3) The ratio of the tensile strengths of IG-110 and IG-430 was estimated from Griffith Theory using the experimental data obtained in this study. The estimated strength ratio was in good agreement with the strength ratio obtained from the supplier's data.

Oral presentation

Pre-irradiation sample size validation on the compressive strength of nuclear graphite for HTGRs

Kunimoto, Eiji; Konishi, Takashi; Eto, Motokuni*; Sumita, Junya; Shibata, Taiju; Sawa, Kazuhiro; Kuroda, Masatoshi*; Kato, Yutai*

no journal, , 

no abstracts in English

Oral presentation

Effect of microstructure on the strength of graphite material for HTGR

Sumita, Junya; Shibata, Taiju; Tachibana, Yukio; Kuroda, Masatoshi*

no journal, , 

no abstracts in English

Oral presentation

Effect of notch-tip geometry on the fracture toughness of fine-grained isotropic graphite

Matsushima, Yuki*; Yamada, Teruaki*; Kuroda, Masatoshi*; Sumita, Junya; Shibata, Taiju; Sawa, Kazuhiro

no journal, , 

In order to investigate the effect of notch-tip geometry on the fracture toughness of fine-grained isotropic graphite ETU-10, three-point-bending fracture toughness tests have been performed by using two types of single-edge notched beam specimens with different notch angles of approximately 15$$^{circ}$$ and 30$$^{circ}$$. The values of the fracture toughness were calculated based on linear elastic fracture mechanics by using the maximum force which could be obtained by the load-displacement curve. As a result, the values of the fracture toughness of the specimens with the notch angles of approximately 15$$^{circ}$$ and 30$$^{circ}$$ were 0.933 MPa m$$^{1/2}$$and 0.926 MPa m$$^{1/2}$$, respectively. This suggested that the values of the fracture toughness were not affected between the notch angles. Further work has been ongoing to discuss the effect of the notch-tip geometry such as angle and root radius of notch in terms of finite element analysis.

Oral presentation

Fatigue properties and fracture mechanism of 2D C/C composite materials

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.

Oral presentation

Fracture mechanism of fine- and coarse-grain graphite

Sumita, Junya; Shibata, Taiju; Tachibana, Yukio; Kuroda, Masatoshi*

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. The Very High Temperature Reactor (VHTR) is one of the most promising candidates as the Generation-IV nuclear reactor systems. During operation of the HTGR, the graphite structure is subjected to various loadings such as external forces and internal stresses resulted from neutron irradiation-induced dimensional and material property changes and a thermal gradient. In order to acquire the fundamental data to evaluate the integrity of the graphite structure of HTGR by fracture mechanics, it is important to investigate the fracture toughness and strain energy release rate of graphite. In this study, the fracture toughness of fine-grain and coarse-grain graphite was measured and calculated the strain energy release rate of them. Moreover, the crack propagation in these graphite and coarse-grain graphite were observed by microscope and the difference between them was discussed from the viewpoint of the grain size.

Oral presentation

Consideration of the hot pressing conditions of the high-strength fuel compact for high-temperature gas-cooled reactor

Yamamoto, Takenori*; Tojo, Takuya*; Kuroda, Masatoshi*; Sumita, Junya; Aihara, Jun; Tachibana, Yukio

no journal, , 

R&D on SiC/C mixed matrix fuel element of high temperature gas-cooled reactors (HTGRs) to improve oxidation resistance of fuel has been started. In this R&D, Young's modulus of fabricated SiC/C mixed matrix dummy fuel elements was measured. In addition, set of fabrication conditions of SiC/C mixed matrix dummy fuel elements was decided for modeling of relationship between fabrication condition and strength of fabricated SiC/C mixed matrix dummy fuel elements to estimate fabrication condition for SiC/C mixed matrix fuel elements with high strength.

Oral presentation

Working Group Session "IRPA Practical Guidance for Engagement with the Public on Radiation and Risk"

Yoshida, Hiroko*; Nomura, Naoki*; Kono, Takahiko; Sakoda, Akihiro; Kuroda, Yujiro*; Naito, Wataru*; Hirota, Seiko*; Kudo, Shinichi*; Etani, Reo*; Chikamoto, Kazuhiko*; et al.

no journal, , 

This working group has been translating into Japanese the publication "Practical Guidance for Engagement with the Public on Radiation and Risk" by IRPA in 2020. This publication was made with the theme of public understanding, which was one of key issues that the consultation by IRPA to its member societies identified as most necessary in the radiation protection system. The translated guidance is supposed to be distributed to radiation protection experts and relevant communities in Japan who may be interested in public understanding. The purpose of this symposium is to share the working progress and important points of the guidance.

Oral presentation

Activity report from IRPA Practical Guidance for Engagement with the Public on Radiation and Risk Working Group

Yoshida, Hiroko*; Nomura, Naoki*; Kono, Takahiko; Sakoda, Akihiro; Kuroda, Yujiro*; Naito, Wataru*; Hirota, Seiko*; Kudo, Shinichi*; Takahara, Shogo; Etani, Reo*; et al.

no journal, , 

The WG has translated the "Practical Guidance for Engagement with the Public on Radiation and Risk" ("IRPA Guidance") issued by the International Radiation Protection Association ("IRPA") to its member societies in 2020. "Practical Guidance for Engagement with the Public on Radiation and Risk" (hereinafter referred to as "IRPA Guidance") published by the International Radiological Protection Association (hereinafter referred to as "IRPA") in 2020 for its member societies, and to provide the information to radiation protection experts and other interested.

Oral presentation

Planning session from IRPA Practical Guidance for Engagement with the Public on Radiation and Risk Working Group

Yoshida, Hiroko*; Nomura, Naoki*; Kono, Takahiko; Sakoda, Akihiro; Kuroda, Yujiro*; Naito, Wataru*; Hirota, Seiko*; Kudo, Shinichi*; Kawaguchi, Isao*; Etani, Reo*; et al.

no journal, , 

The WG has translated the "Practical Guidance for Engagement with the Public on Radiation and Risk" ("IRPA Guidance") issued by the International Radiation Protection Association ("IRPA") to its member societies in 2020. "The content of the IRPA guidance was presented at a symposium organized by the Health Physics Society of Japan in June 2020. The content of the IRPA guidance was presented at the Health Physics Society planning symposium held in June 2020, where many experts attended and provided feedback. In this planning session, we will focus on public engagement and related specific examples and situations related to public engagement.

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