Kitazawa, Takafumi; Ikeda, Yoichi*; Sakakibara, Toshiro*; Matsuo, Akira*; Shimizu, Yusei*; Tokunaga, Yo; Haga, Yoshinori; Kindo, Koichi*; Nambu, Yusuke*; Ikeuchi, Kazuhiko*; et al.
Physical Review B, 108(8), p.085105_1 - 085105_7, 2023/08
Oda, Chie; Kawama, Daisuke*; Shimizu, Hiroyuki*; Benbow, S. J.*; Hirano, Fumio; Takayama, Yusuke; Takase, Hiroyasu*; Mihara, Morihiro; Honda, Akira
Journal of Advanced Concrete Technology, 19(10), p.1075 - 1087, 2021/10
Concrete in a transuranic (TRU) waste repository is considered a suitable material to ensure safety, provide structural integrity and retard radionuclide migration after the waste containers fail. In the current study, coupling between chemical, mass-transport and mechanical, so-called non-linear processes that control concrete degradation and crack development were investigated by coupled numerical models. Application of such coupled numerical models allows identification of the dominant non-linear processes that will control long-term concrete degradation and crack development in a TRU waste repository.
Takahashi, Atsushi*; Chiba, Mirei*; Tanahara, Akira*; Aida, Jun*; Shimizu, Yoshinaka*; Suzuki, Toshihiko*; Murakami, Shinobu*; Koarai, Kazuma; Ono, Takumi*; Oka, Toshitaka; et al.
Scientific Reports (Internet), 11(1), p.10355_1 - 10355_11, 2021/05
Ishimaru, Tsuneari; Ogata, Nobuhisa; Kokubu, Yoko; Shimada, Koji; Hanamuro, Takahiro; Shimada, Akiomi; Niwa, Masakazu; Asamori, Koichi; Watanabe, Takahiro; Sueoka, Shigeru; et al.
JAEA-Research 2020-011, 67 Pages, 2020/10
This annual report documents the progress of research and development (R&D) in the 5th fiscal year during the JAEA 3rd Mid- and Long-term Plan (fiscal years 2015-2021) to provide the scientific base for assessing geosphere stability for long-term isolation of the high-level radioactive waste. The planned framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques. The current status of R&D activities with previous scientific and technological progress is summarized.
Komatsu, Yuya*; Shimizu, Ryota*; Wilde, M.*; Kobayashi, Shigeru*; Sasahara, Yuki*; Nishio, Kazunori*; Shigematsu, Kei*; Otomo, Akira*; Fukutani, Katsuyuki; Hitosugi, Taro*
Crystal Growth & Design, 20(9), p.5903 - 5907, 2020/09
Benbow, S. J.*; Kawama, Daisuke*; Takase, Hiroyasu*; Shimizu, Hiroyuki*; Oda, Chie; Hirano, Fumio; Takayama, Yusuke; Mihara, Morihiro; Honda, Akira
Crystals (Internet), 10(9), p.767_1 - 767_33, 2020/09
Details are presented of the development of a coupled modeling simulator for assessing the evolution in the near-field of a geological repository for radioactive waste disposal where concrete is used as a backfill. The simulator uses OpenMI, a standard for exchanging data between simulation software programs at run-time, to form a coupled chemical-mechanical-hydrogeological model of the system. The approach combines a tunnel scale stress analysis finite element model, a discrete element model for accurately modeling the patterns of emerging cracks in the concrete, and a finite element and finite volume model of the chemical processes and alteration in the porous matrix and cracks in the concrete, to produce a fully coupled model of the system. Combining existing detailed simulation software in this way with OpenMI has the benefit of not relying on simplifications that might be necessary to combine all of the modeled processes in a single piece of software.
Ishimaru, Tsuneari; Ogata, Nobuhisa; Shimada, Koji; Kokubu, Yoko; Niwa, Masakazu; Asamori, Koichi; Watanabe, Takahiro; Sueoka, Shigeru; Komatsu, Tetsuya; Yokoyama, Tatsunori; et al.
JAEA-Review 2020-010, 46 Pages, 2020/07
This report is a plan of research and development (R&D) on geosphere stability for long-term isolation of high-level radioactive waste (HLW) in Japan Atomic Energy Agency (JAEA), in fiscal year 2020. The objectives and contents in fiscal year 2020 are described in detail based on the JAEA 3rd Medium- and Long-term Plan (fiscal years 2015-2021). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. The plan framework is structured into the following categories: (1) Development and systematization of investigation techniques, (2) Development of models for long-term estimation and effective assessment, (3) Development of dating techniques.
Strasser, P.*; Abe, Mitsushi*; Aoki, Masaharu*; Choi, S.*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; et al.
EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01
Hirano, Fumio; Otani, Yoshiteru*; Kyokawa, Hiroyuki*; Mihara, Morihiro; Shimizu, Hiroyuki*; Honda, Akira
Nihon Genshiryoku Gakkai Wabun Rombunshi, 15(2), p.97 - 114, 2016/06
A mechanical analysis code MACBECE2014 has been developed at the Japan Atomic Energy Agency to make realistic simulations of the physical integrity of the near-field for performance assessment of geological disposal of TRU waste in Japan. The MACBECE2014 code can be used to evaluate long-term changes in the mechanical behavior and any subsequent changes in the permeability of engineering barrier components, including crack formation in cementitious materials caused by expansion due to metal corrosion. Simulated results of the TRU waste disposal system with a bentonite buffer using the MACBECE2014 code demonstrated that the low permeability of the engineering barrier system could be maintained for long time periods after disposal because the physical integrity of the bentonite buffer remained intact. Simulated results of the disposal system with a concrete backfill, showed that crack formation leads to a significant increase in permeability of the system.
Fujinami, Shun*; Takeda, Kiyoko*; Onodera, Takefumi*; Sato, Katsuya; Shimizu, Tetsu*; Wakabayashi, Yu*; Narumi, Issey*; Nakamura, Akira*; Ito, Masahiro*
Genome Announcements (Internet), 3(5), p.e01005-15_1 - e01005-15_2, 2015/09
Satoh, Daiki; Maeda, Yoshikazu*; Tameshige, Yuji*; Nakashima, Hiroshi; Shibata, Tokushi*; Endo, Akira; Tsuda, Shuichi; Sasaki, Makoto*; Maekawa, Motokazu*; Shimizu, Yasuhiro*; et al.
Journal of Nuclear Science and Technology, 49(11), p.1097 - 1109, 2012/11
At the Fukui Prefectural Hospital Proton Therapy Center, neutron doses behind concrete shields and at maze have been measured by using radiation monitors, DARWIN, Wendi-2, a rem meter, and solid state nuclear track detectors. The measured data were compared with the estimations by analytical models and Monte Carlo code PHITS. The analytical model with the parameters employed in shielding design of the facility gave considerably larger estimates than the measured data. This means that the facility was designed with an enough safety margin. The calculation results of PHITS were less than those of the analytical model, and were about 3 times larger than the measured data. From the view point of a safety policy with conservative estimation for shielding design, Monte Carlo simulation is a better tool for estimating radiation safety at accelerator-based proton treatment facilities.
Sugimoto, Masahiro*; Kosugi, Keizo*; Katayama, Kota*; Ii, Hideki*; Takagi, Akira*; Endo, Sakaru*; Shimizu, Hitoshi*; Tsubouchi, Hirokazu*; Kizu, Kaname; Yoshida, Kiyoshi
Proceedings of 24th International Cryogenic Engineering Conference (ICEC 24) and International Cryogenic Materials Conference 2012 (ICMC 2012) (CD-ROM), p.799 - 802, 2012/05
We have successfully manufactured all superconducting cables for CS and EF coils of JT-60SA. The low temperature performance of superconducting wires satisfied the specifications under sufficiently low deviations and high production yields. Ni-plated strands of EF cables having the larger sliding friction between strands than that of Cr-plated strands of CS cable caused difficulties on the cabling without any defects. Consequently, the newly developed cabling techniques with the original inspection apparatus significantly enhanced the manufacturability and were effective for guarantee of the quality.
Chijimatsu, Masakazu*; Koyama, Tomofumi*; Kobayashi, Akira*; Shimizu, Hiroyuki*; Nakama, Shigeo
Proceedings of 4th International Conference on Coupled T-H-M-C Processes in Geosystems: Fundamentals, Modeling, Experiments and Applications (GeoProc 2011) (CD-ROM), 13 Pages, 2011/07
The experiment was performed at the sp Hard Rock Laboratory facility owned by the Swedish Nuclear Fuel and Waste Management Co. For the experiment an oval shape tunnel was excavated in which two large holes, 1.75 m and depth 6.5 m, were excavated. The holes were placed so that a 1 m wide vertical pillar was created between them. The pillar volume was then heated to increase the tangential stress so that yielding could propagate along the borehole wall. Analysis of the coupled thermal, hydraulic and mechanical processes is carried out with the computer code named THAMES. In order to evaluate the spalling phenomena, the damage model was included in the computer code. In the damage mechanics, the change in mechanical behavior due to the growth of damage (cracks) in material is considered. The parameters of this damage model were determined by the unconfined compression test. When the parameters determined by laboratory test were used, the damage did not occur. This is because the parameters were determined from the experiment of the rock core, and it is thought that the parameter of actual bedrock is inferior to that of the rock core. Therefore, the calibration of the damage parameters was performed. When the calibrated parameters were used, simulation results agree qualitatively well with the experimental results. During the simulation of excavation, generating of damage is seen to similar to the observation by the in-situ experiment. Furthermore, temperature change during heating after the excavation of borehole also shows the good agreement between the measured and simulated results. Therefore, it can be said that the spalling phenomenon is expressible even by the application with the continuum model by the use of the suitable parameters.
Koyama, Tomofumi*; Shimizu, Hiroyuki*; Chijimatsu, Masakazu*; Kobayashi, Akira*; Nakama, Shigeo; Fujita, Tomoo
Proceedings of 4th International Conference on Coupled T-H-M-C Processes in Geosystems: Fundamentals, Modeling, Experiments and Applications (GeoProc 2011) (CD-ROM), 11 Pages, 2011/07
In this paper, the coupled thermal-mechanical processes in the pillar stability experiments carried out at the sp Hard Rock Laboratory by the Swedish Nuclear Fuel and Waste Management Company (SKB) were simulated using both Finite Element Method (FEM) and Distinct Element Method (DEM) with particles. The main purpose for in-situ experiment is to investigate the yielding strength of crystalline rock and the formation and growth of the excavation disturbed/damaged zone (EDZ) during excavation and heating processes. For the 3-D numerical simulations using FEM (called THAMES), the measured in-situ stress and its time evolutions (stress re-distribution) due to the tunnel and two borehole excavations, pressurize in one of the borehole as well as heating process were considered. On the other hand, in 2-D DEM simulations, one of the borehole cross sections (in 2-D) was selected and modeled as an assemblage of many particles bonded each other to investigate the failure mechanism during excavation and heating processes in detail including crack propagation at the borehole surface (spalling phenomena). The microscopic parameters used in the DEM simulations were determined by the calibration using the laboratory uniaxial/triaxial compression testing results. The calculation results such as stress distribution, displacements as well as temperature distribution were compared with the in-situ observation and measurements. The simulation results from 3-D FEM shows good agreement with the data obtained from the measurements. The simulated crack propagation during the excavation, pressurizing and heating processes by DEM with particles agrees qualitatively well with the observation. The findings obtained from two different types of numerical simulations can be used for the performance and safety assessment of nuclear waste disposal.
Sakurai, Shinji; Kawashima, Hisato; Higashijima, Satoru; Shimizu, Katsuhiro; Masaki, Kei; Asakura, Nobuyuki; Shibama, Yusuke; Sakasai, Akira
Journal of Nuclear Materials, 390-391, p.891 - 894, 2009/06
The entire plasma facing components should be water-cooled in JT-60SA. A cassette module of divertor is introduced for remote maintenance. The divertor targets are mounted on the cassette. A brazed carbon fiber composite target is promising candidate for the divertor target. The latest results of mock-ups test clarified that thermal fatigue life cycles are more than 1000 cycles of 15 MW/m10 sec. The divertor is designed to control divertor detachment for heat load reduction. The vertical targets and a "V-shaped corner" like as that in ITER are adopted to enhance detachment. Divertor heat load and pumping efficiency has been evaluated, using 2D plasma fluid (SOLDOR) and neutral Monte-Carlo (NEUT2D) code. The plasma detachment occurs near the outer-strike point within the "V-shaped corner", which results in low peak heat flux density 5.8 MW/m for the case with additional gas puff of 510/s compared to 11.4 MW/m for the case without "V-shaped corner".
Okamura, Masachika*; Shimizu, Akira*; Onishi, Noboru*; Hase, Yoshihiro; Yoshihara, Ryohei; Narumi, Issei
JAEA-Review 2008-055, JAEA Takasaki Annual Report 2007, P. 62, 2008/11
no abstracts in English
Shibata, Akira; Kawamata, Kazuo; Taguchi, Taketoshi; Kaji, Yoshiyuki; Shimizu, Michio*; Kanazawa, Yoshiharu; Matsui, Yoshinori; Iwamatsu, Shigemi; Sozawa, Shizuo; Tayama, Yoshinobu; et al.
JAEA-Technology 2008-029, 40 Pages, 2008/03
Irradiation assisted stress corrosion cracking (IASCC) is considered to be one of the key issues from a viewpoint of the life management of core components in the aged Light Water Reactors. The in-situ crack extension examination and the in-situ constant load tensile test in the reactor are required for the study of IASCC. There are, however, some technical hurdles to be overcome for the experiments. For this in-situ IASCC test, techniques for assembling pre-irradiated specimens into an capsule in a hot cell by remote handling are necessary. In this report, I describe the establishment of those remote assembling techniques and development of new welding apparatus and the TIG upset welding for stainless tube of 3 mm in thickness. Already IASCC capsules having pre-irradiated CT specimens were remotely assembled using these techniques in the hot cell for performing crack growth tests under irradiation in JMTR. And eight in-situ IASCC capsules have been finished successfully in JMTR.
Okamura, Masachika*; Shimizu, Akira*; Watanabe, Satomi*; Hase, Yoshihiro; Narumi, Issei; Tanaka, Atsushi
JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 82, 2008/03
no abstracts in English
Kubo, Hirotaka; Sasaki, Akira; Moribayashi, Kengo; Higashijima, Satoru; Takenaga, Hidenobu; Shimizu, Katsuhiro; Nakano, Tomohide; Whiteford, A.*; Sugie, Tatsuo
Journal of Nuclear Materials, 363-365, p.1441 - 1445, 2007/06
no abstracts in English
Okamura, Masachika*; Momose, Masayuki*; Watanabe, Satomi*; Shimizu, Akira*; Hase, Yoshihiro; Yokota, Yuichiro; Tanaka, Atsushi
JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 82, 2007/02
no abstracts in English