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Nara, Yoshitaka*; Kashiwaya, Koki*; Oketani, Kazuki*; Fujii, Hirokazu*; Zhao, Y.*; Kato, Masaji*; Aoyagi, Kazuhei; Ozaki, Yusuke; Matsui, Hiroya; Kono, Masanori*
Zairyo, 73(3), p.220 - 225, 2024/03
The fractures in the rock are the main pass of groundwater flow and solute transport. The filling of fine-grained particle, such as clay minerals, was confirmed to decrease the permeability of rock by laboratory experiment. This research aimed to verify the occurrence of the phenomena in the field. The water containing the clay minerals was injected into the rock at the 200m stage of the Mizunami Underground research laboratory. The hydraulic conductivity decreased two order before and after the injection. This result suggested that the decrease of hydraulic conductivity by the filling of fine-grained particle in the fractures occurred in the real field.
Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Nara, Yoshitaka*; Kato, Masaji*; Sato, Tsutomu*; Kono, Masanori*; Sato, Toshinori
Journal of MMIJ, 138(4), p.44 - 50, 2022/04
It is important to understand the long-term migration of radionuclides when considering rock engineering projects such as the geological disposal of radioactive waste. The network of fractures and pores in a rock mass plays a major role in fluid migration as it provides a pathway for fluid flow. The geometry of a network can change due to fracture sealing by some fine-grained materials over long-term periods. In the present study, we use a macro-fractured granite sample to investigate the change of permeability that occurs under the flow of water that includes two different amounts of clay. Findings showed that clay accumulated in a fracture and that the permeability (hydraulic conductivity) of the granite sample decreased over time, which was greater in for the higher clay content. We concluded that the accumulation of clay minerals in the fracture decreased the permeability of the rock. Furthermore, we consider that the filling and closure of fractures in rock is possible under the flow of groundwater that includes clay minerals.
Kondo, Yasuhiro; Hirano, Koichiro; Ito, Takashi; Kikuzawa, Nobuhiro; Kitamura, Ryo; Morishita, Takatoshi; Oguri, Hidetomo; Okoshi, Kiyonori; Shinozaki, Shinichi; Shinto, Katsuhiro; et al.
Journal of Physics; Conference Series, 1350, p.012077_1 - 012077_7, 2019/12
Times Cited Count：1 Percentile：51.97(Physics, Particles & Fields)We have upgraded a 3-MeV linac at J-PARC. The ion source is same as the J-PARC linac's, and the old 30-mA RFQ is replaced by a spare 50-mA RFQ, therefore, the beam energy is 3 MeV and the nominal beam current is 50 mA. The main purpose of this system is to test the spare RFQ, but also used for testing of various components required in order to keep the stable operation of the J-PARC accelerator. The accelerator has been already commissioned, and measurement programs have been started. In this paper, present status of this 3-MeV linac is presented.
Nara, Yoshitaka*; Kato, Masaji*; Sato, Tsutomu*; Kono, Masanori*; Sato, Toshinori
Proceedings of 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future (YSRM 2019 and REIF 2019) (USB Flash Drive), 6 Pages, 2019/12
It is important to understand the long-term migration of radionuclides considering carious rock engineering projects such as the geological disposal of radioactive wastes. The network of fractures and pores in a rock mass can play important roles as the pathway of the fluid flow of rock. Usually groundwater contains fine-grained minerals such as clays. It is probable that the accumulation of the fine-grained minerals occurs in a fracture if the groundwater flows in a fracture in a rock. In this study, we have conducted the permeability measurement using water including clays. Specifically, we used a macro-fractured granite as a rock sample, and investigated the change of the permeability under the flow of the water including clays. It was shown that the hydraulic conductivity decreased with elapsed time.
Kato, Masaji*; Nara, Yoshitaka*; Okazaki, Yuki*; Kono, Masanori*; Sato, Toshinori; Sato, Tsutomu*; Takahashi, Manabu*
Materials Transactions, 59(9), p.1427 - 1432, 2018/09
Times Cited Count：6 Percentile：32.18(Materials Science, Multidisciplinary)To ensure the safe geological disposal of radioactive waste, it is important to determine the permeability (hydraulic conductivity) of clays. The transient pulse method is suitable for low-permeability materials because it requires a relatively short time to determine their permeability. Upstream pore pressure typically increases in the measurement conducted via the transient pulse method. However, this procedure cannot be used to determine the permeability of clays due to the increase in pore pressure. Therefore, the transient pulse method has never been applied to determine clay permeability. In this study, we applied the transient pulse method to a clay sample to determine its permeability while decreasing the downstream pore pressure.
Nara, Yoshitaka*; Kato, Masaji*; Niri, Ryuhei*; Kono, Masanori*; Sato, Toshinori; Fukuda, Daisuke*; Sato, Tsutomu*; Takahashi, Manabu*
Pure and Applied Geophysics, 175(3), p.917 - 927, 2018/03
Times Cited Count：14 Percentile：57.88(Geochemistry & Geophysics)Information on the permeability of rock is essential for various geoengineering projects. It is especially important to investigate how fractures and pores influence the physical and transport properties of rock. Infiltration of groundwater through the damage zone fills fractures in granite with fine-grained minerals. However, the permeability of rock possessing a fracture naturally filled with fine-grained mineral grains has yet to be investigated. In this study, the permeabilities of granite samples, including a macro-fracture filled with clay and a mineral vein, are investigated. The permeability of granite with a fine-grained mineral vein agrees well with that of the intact sample, whereas the permeability of granite possessing a macro-fracture filled with clay is lower than that of the macro-fractured sample. The decrease in the permeability is due to the filling of fine-grained minerals and clay in the macro-fracture. It is concluded that the permeability of granite increases due to the existence of the fractures, but decreases upon filling them with fine-grained minerals.
Kato, Masaji*; Nara, Yoshitaka*; Okazaki, Yuki*; Kono, Masanori*; Sato, Toshinori; Sato, Tsutomu*; Takahashi, Manabu*
Zairyo, 67(3), p.318 - 323, 2018/03
To ensure the safe geological disposal of radioactive wastes, it is important to determine the permeability of clays. The transient pulse test is suitable to apply to the low permeability materials, because it takes relatively short term to determine the permeability. Usually we increase the upstream pore pressure in the measurement with the transient pulse test. However, it is impossible to determine the permeability of clay in this procedure because of the increase of pore pressure. Therefore, the transient pulse test has never been applied to the determination of permeability of clays. In this study, we tried to apply the transient pulse test to a clay obtained in Mizunami Underground Research Laboratory to determine the permeability with decreasing the downstream pore pressure. It was clarified that the transient pulse test with decreasing downstream pore pressure is appropriate from the measurements of granite and sandstone. It was shown that the permeability of a clay was determined by the transient pulse test with decreasing the downstream pore pressure, which agreed with the permeability determined from the falling head test. The measurement time of the transient pulse test is much shorter than that of the falling head test. It is concluded that the transient pulse test is appropriate for the determination of the permeability of clays.
Wakai, Takashi; Kobayashi, Sumio; Kato, Shoichi; Ando, Masanori; Takasho, Hideki*
Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 7 Pages, 2017/07
This paper describes a thermal fatigue test on a structural model with a dissimilar welded joint. In the present design of JSFR, there may be dissimilar welded joints between ferritic and austenitic steels especially in IHX and SG. Creep-fatigue is one of the most important failure modes in JSFR components. However, the creep-fatigue damage evaluation method has not been established for dissimilar welded joint. To investigate the evaluation method, structural test will be needed for verification. Therefore, a thermal fatigue test on a thick-wall cylinder with a circumferential dissimilar welded joint between Mod.9Cr-1Mo steel and 304SS was performed. Since the coefficients of thermal expansion of these steels were significantly different, buttering layer of Ni base alloy was installed between them. After the completion of the test, deep cracks were observed at the HAZ in 304SS, as well as at HAZ in Mod.9Cr-1Mo steel. There were many tiny surface cracks in BM of 304SS. According to the fatigue damage evaluation based on the finite element analysis results, the largest fatigue damage was calculated at HAZ in 304SS. Large fatigue damage was also estimated at BM of 304SS. Fatigue cracks were observed at HAZ and BM of 304SS in the test, so that analytical results are in a good agreement with the observations. However, though relatively small fatigue damage was estimated at HAZ in Mod.9Cr-1Mo steel, deep fatigue cracks were observed in the test. To identify the cause of such a discrepancy between the test and calculations, we performed a series of finite element analyses. Some metallurgical investigations were also performed.
Kato, Masaji*; Nara, Yoshitaka*; Fukuda, Daisuke*; Kono, Masanori*; Sato, Toshinori; Sato, Tsutomu*; Takahashi, Manabu*
Zairyo, 65(7), p.489 - 495, 2016/07
Rock masses serve a vital function as natural barriers for geological disposal of radioactive waste; therefore, information on rock permeability is essential. Highly accurate measurement of permeability requires understanding of how temperature changes in the surrounding environment influence measurement results. We performed permeability measurement under conditions with dramatic changes of temperature in the surrounding environment to investigate the influence of such changes on the experimental results. Measurement of permeability with no temperature change was also conducted as reference. All measurements were conducted using the transient pulse method, and the sample material used was Toki granite obtained from Gifu Prefecture in central Japan. We found that temperature changes in the surrounding environment remarkably affected the pressure in reservoirs upstream and downstream, the pressure difference between them, and the confining pressure; all increased when temperature increased for our experimental system. Notably, pressure difference was affected immediately. This difference directly relates to estimation of permeability.
Higashi, Yoichi*; Nagai, Yuki; Yoshida, Tomohiro*; Kato, Masaru*; Yanase, Yoichi*
Physica C, 518, p.1 - 4, 2015/11
Times Cited Count：0 Percentile：0(Physics, Applied)We study the excitation spectra and the wave functions of quasiparticle bound states at a vortex and an edge in bilayer Rashba superconductors under a magnetic field. In particular, we focus on the quasiparticle states at the zero energy in the pair- density wave state in a topologically non-trivial phase. We numerically demonstrate that the quasiparticle wave functions with zero energy are localized at both the edge and the vortex core if the magnetic field exceed the critical value.
Irisawa, Eriko; Seki, Masaharu*; Ueno, Fumiyoshi; Kato, Chiaki; Motooka, Takafumi; Abe, Hitoshi
Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.1108 - 1112, 2015/09
Shimomura, Kenta; Kato, Shoichi; Wakai, Takashi; Ando, Masanori; Hirose, Yuichi*; Sato, Kenichiro*
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 9 Pages, 2015/05
This paper describes experimental and analytical works to confirm that the design standard for SFR components sufficiently covers possible failure mechanisms. Creep-fatigue damage evaluation method in JSME design standard for SFR components has been constructed based on experiments and/or numerical analyses of conventional austenitic stainless steels, such as 304SS. Since the material characteristics of Mod.9Cr-1Mo steel are substantially different from those of austenitic stainless steels, it is required to verify the applicability of the design standards to the SFR components made of Mod.9Cr-1Mo steel. A series of uni-axial creep-fatigue tests were conducted using double-ended notch bar specimens made of Mod.9Cr-1Mo steel under displacement controlled condition with 30 minute holding. The curvature radii of the specimens were 1.6mm, 11.2mm and 40.0mm. The specimen having 1.6mm notch and 11.2mm notch failed from outer surface but the specimen having 40.0mm notch showed obvious internal crack nucleation. In addition, though total duration time of the creep-fatigue test was only 2,000 hours, a lot of creep voids and inter granular crack growth were observed. To clarify the cause of such peculiar failure, some additional experiments were performed, as well as some numerical analyses. We could point out that such a peculiar failure aspect might result from corresponding stress distribution in the cross section. As a result of a series of investigations, possible causes of such peculiar failure could be narrowed down. A future investigation plan was proposed to clarify the most significant cause.
Sato, Takeshi; Muto, Shigeo; Akiyama, Kiyomitsu; Aoki, Kazufumi; Okamoto, Akiko; Kawakami, Takeshi; Kume, Nobuhide; Nakanishi, Chika; Koie, Masahiro; Kawamata, Hiroyuki; et al.
JAEA-Review 2014-048, 69 Pages, 2015/02
JAEA-Review-2014-048.pdf:13.91MB
JAEA was assigned as a designated public institution under the Disaster Countermeasures Basic Act and under the Armed Attack Situations Response Act. Based on these Acts, the JAEA has the responsibility of providing technical support to the national government and/or local governments in case of disaster responses or response in the event of a military attack, etc. In order to fulfill the tasks, the JAEA has established the Emergency Action Plan and the Civil Protection Action Plan. In case of a nuclear emergency, NEAT dispatches specialists of JAEA, supplies the national government and local governments with emergency equipment and materials, and gives technical advice and information. In normal time, NEAT provides various exercises and training courses concerning nuclear disaster prevention to those personnel taking an active part in emergency response institutions of the national and local governments, police, fire fighters, self-defense forces, etc. in addition to the JAEA itself. The NEAT also researches nuclear disaster preparedness and response, and cooperates with international organizations. In the FY2013, the NEAT accomplished the following tasks: (1) Technical support activities as a designated public institution in cooperation with the national and local governments, etc. (2) Human resource development, exercise and training of nuclear emergency response personnel for the national and local governments, etc. (3) Researches on nuclear disaster preparedness and response, and sending useful information (4) International contributions to Asian countries on nuclear disaster preparedness and response in collaboration with the international organizations
Kato, Nobuyoshi*; Tsusaka, Kimikazu; Nago, Makito*; Yamagami, Masahito*; Matsubara, Makoto*; Shigehiro, Michiko*; Aizawa, Takao*; Kamemura, Katsumi*
Chishitsu To Chosa, (139), p.17 - 22, 2014/04
no abstracts in English
Katsuyama, Chie*; Nashimoto, Hiroaki*; Nagaosa, Kazuyo*; Ishibashi, Tomotaka*; Furuta, Kazuki*; Kinoshita, Takeshi*; Yoshikawa, Hideki; Aoki, Kazuhiro; Asano, Takahiro*; Sasaki, Yoshito; et al.
FEMS Microbiology Ecology, 86(3), p.532 - 543, 2013/12
Times Cited Count：14 Percentile：36.52(Microbiology)Anaerobic microbial activity has a major influence on the subsurface environment, and should be considered in subsurface activities including the construction of radioactive waste repositories. We investigated denitrification and methanogenesis in anoxic groundwater from 140 m depth in two boreholes, where the redox potential fluctuated. The average maximum potential denitrification rates, measured under anaerobic conditions in the two boreholes using an 
N tracer. Methanogenesis candidates were detected by 16S rRNA gene analysis. Although the stable isotope signatures suggested that some of the dissolved methane was of biogenic origin, no potential for methane production was evident during the incubations. The groundwater at 140 m depth did not contain oxygen, had an Eh ranging from -144 to 6.8 mV, and was found to be a potential field for denitrification.
Ueda, Yoshio*; Oya, Kaoru*; Ashikawa, Naoko*; Ito, Atsushi*; Ono, Tadayoshi*; Kato, Daiji*; Kawashima, Hisato; Kawamura, Gakushi*; Kenmotsu, Takahiro*; Saito, Seiki*; et al.
Purazuma, Kaku Yugo Gakkai-Shi, 88(9), p.484 - 502, 2012/09
no abstracts in English
Al
Ni
Cu
bulk metallic glass containing ZrC particles by synchrotron X-ray diffractionSuzuki, Hiroshi; Saida, Junji*; Shobu, Takahisa; Katsuyama, Jinya; Kato, Hidemi*; Imafuku, Muneyuki*; Sato, Shigeo*
Scripta Materialia, 66(10), p.801 - 804, 2012/05
Times Cited Count：6 Percentile：37.79(Nanoscience & Nanotechnology)Compressive deformation mechanism of a ZrAlNiCu bulk metallic glass containing 10vol.%ZrC (ZrC-BMG) was evaluated by measuring the residual strains in the compressive deformed samples using the synchrotron X-ray diffraction and also evaluating the localized deformation behavior around the ZrC particles by the finite element analysis. Phase stress shared by the metallic glass matrix was increased before macroscopic yielding due to local plastic deformation around the ZrC particles. After macroscopic yielding, the phase stress shared by the ZrC phase was drastically increased, and finally the ZrC-BMG was fractured by breaking the ZrC particles reaching its fracture strength.
Sudo, Katsuo; Takano, Tatsuo; Takeuchi, Kentaro; Kihara, Yoshiyuki; Kato, Masato
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 5 Pages, 2011/12
Japan Atomic Energy Agency has been contracted to advance the Fast Reactor Cycle Technology Development project. As one part of the project, a simplified MOX pellet fabrication method has been developed for fast reactor fuels. In previous reports, feasibility of a simplified MOX pellet fabrication method was confirmed through hot and cold laboratory-scale experiments. The die wall lubrication pressing technology was one of the important technologies included in the development of the simplified MOX pellet fabrication method. In the work described here, a pressing machine with a die wall lubrication system was developed, and MOX pellet fabrication experiments were carried out on the kilogram MOX scale.
Takano, Tatsuo; Sudo, Katsuo; Takeuchi, Kentaro; Kihara, Yoshiyuki; Kato, Masato
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 7 Pages, 2011/12
Development of high burn-up fuels is essential to improve economy of the fast reactor fuel cycle. Increase of fuel burn-up is known to cause fuel-cladding chemical interaction (FCCI) and it mainly determines a lifetime of fuel pin. In order to extend a lifetime of fuel pin by mitigating FCCI, development of low oxygen-to-metal (O/M) MOX fuel has been carried out in plutonium fuel development center of JAEA. MOX fuel needs adjustment of the O/M ratio to less than 1.97 for high burn-up of 150 GWd/t. Therefore, O/M adjustment technology is one of the main subjects in development of a simplified MOX pellet fabrication method which has been advanced in the FaCT (Fast reactor Cycle Technology development) project. In previous work, changes in O/M ratio of MOX pellet during heat treatment were calculated from measurement results of oxygen potentials. On the basis of above calculation, heating tests were carried out to prepare low O/M ratio MOX pellets on a laboratory scale. The O/M ratios obtained in the heating tests were well consistent with calculation results. In the present study, a kilogram MOX scale furnace to adjust O/M ratio of MOX pellets for targeted value has been developed as next step.
