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Journal Articles

Improved performance of wide bandwidth neutron-spin polarizer due to ferromagnetic interlayer exchange coupling

Maruyama, Ryuji; Yamazaki, Dai; Aoki, Hiroyuki; Akutsu, Kazuhiro*; Hanashima, Takayasu*; Miyata, Noboru*; Soyama, Kazuhiko; Bigault, T.*; Saerbeck, T.*; Courtois, P.*

Journal of Applied Physics, 130(8), p.083904_1 - 083904_10, 2021/08

 Times Cited Count:0 Percentile:0(Physics, Applied)

Journal Articles

Characteristics of fault fracture zones of the activated Shionohira Fault and the non-activated Kuruma Fault of the 2011 Fukushima-ken Hamadori Earthquake, Northeast Japan

Aoki, Kazuhiro; Tanaka, Yukumo; Yoshida, Takumi; Shimada, Koji; Sakai, Toru*; Kametaka, Masao*; Seshimo, Kazuyoshi

Oyo Chishitsu, 62(2), p.64 - 81, 2021/06

Co-seismic surface ruptures in the Fukushima-ken Hamadori Earthquake of Mw 6.7 on April 11, 2011 exposed approximately 14 km trending NNW-SSE from Nameishi to northwest of Ishizumi Tsunaki of Tabito Town, Iwaki City and were newly named the Shionohira Fault. However, no surface ruptures appeared along an N-S trending active Kuruma fault extending 5 km south of the Shionohira Fault. Because of the proximity and similar strike, two locations in Shionohira Fault and one location in Kuruma fault were selected as the study area for the fault activity evaluation. The present study reports the results of a series of geological and drilling surveys, core observation, XRD, isotope, and fluid inclusion analyses, and water permeability test. The results obtained from the three locations offer a fundamental data base that can be utilized for fault activity evaluation by summarizing the geological, mineralogical, and fluid property characteristics of fault fracture zone.

Journal Articles

Improvement in sputtering rate uniformity over large deposition area of large-scale ion beam sputtering system

Maruyama, Ryuji; Yamazaki, Dai; Akutsu, Kazuhiro*; Hanashima, Takayasu*; Miyata, Noboru*; Aoki, Hiroyuki; Soyama, Kazuhiko

JPS Conference Proceedings (Internet), 33, p.011092_1 - 011092_6, 2021/03

no abstracts in English

Journal Articles

Fine-structure analysis of perhydropolysilazane-derived nano layers in deep-buried condition using polarized neutron reflectometry

Akutsu, Kazuhiro*; Kira, Hiroshi*; Miyata, Noboru*; Hanashima, Takayasu*; Miyazaki, Tsukasa*; Kasai, Satoshi*; Yamazaki, Dai; Soyama, Kazuhiko; Aoki, Hiroyuki

Polymers (Internet), 12(10), p.2180_1 - 2180_10, 2020/10

 Times Cited Count:0 Percentile:0(Polymer Science)

Journal Articles

Development of high-polarization Fe/Ge neutron polarizing supermirror; Possibility of fine-tuning of scattering length density in ion beam sputtering

Maruyama, Ryuji; Yamazaki, Dai; Akutsu, Kazuhiro*; Hanashima, Takayasu*; Miyata, Noboru*; Aoki, Hiroyuki; Takeda, Masayasu; Soyama, Kazuhiko

Nuclear Instruments and Methods in Physics Research A, 888, p.70 - 78, 2018/04

 Times Cited Count:3 Percentile:45.99(Instruments & Instrumentation)

The multilayer structure of Fe/Si and Fe/Ge systems fabricated by ion beam sputtering (IBS) was investigated using X-ray and polarized neutron reflectivity measurements and scanning transmission electron microscopy with energy-dispersive X-ray analysis. The obtained result revealed that the incorporation of sputtering gas particles (Ar) in the Ge layer gives rise to a marked reduction in the neutron scattering length density (SLD) and contributes to the SLD contrast between the Fe and Ge layers almost vanishing for spin-down neutrons. This leads to a possibility of fine-tuning of the SLD for the IBS, which is required to realize a high polarization efficiency of a neutron polarizing supermirror. Fe/Ge polarizing supermirror with $$m=5$$ fabricated showed a spin-up reflectivity of 0.70 at the critical momentum transfer. The polarization was higher than 0.985 for the $$q_z$$ range where the correction for the polarization inefficiencies of the beamline works properly.

Journal Articles

Examination of evaluation method for fault activity based on morphological observation of fault planes

Tanaka, Yoshihiro*; Kametaka, Masao*; Okazaki, Kazuhiko*; Suzuki, Kazushige*; Seshimo, Kazuyoshi; Aoki, Kazuhiro; Shimada, Koji; Watanabe, Takahiro; Nakayama, Kazuhiko

Oyo Chishitsu, 59(1), p.13 - 27, 2018/04

This paper aims to develop a methodology for understanding the fault activity by observing exposed fault planes without covering younger strata. Based on purpose, faults developed in relatively homogeneous rocks such granitic types are investigated as follows; Gosuke Dam upstream outcrop of Gosukebashi Fault and Funasaka-nishi outcrop of Rokkou Fault were selected for the study of an active fault; and K-3 outcrop of Rokkou Houraikyo Fault was chosen for a non-active fault.

Journal Articles

Microscopic features of quartz and clay particles from fault gouges and infilled fractures in granite; Discriminating between active and inactive faulting

Niwa, Masakazu; Shimada, Koji; Aoki, Kazuhiro; Ishimaru, Tsuneari

Engineering Geology, 210, p.180 - 196, 2016/08

 Times Cited Count:9 Percentile:53.7(Engineering, Geological)

This study focused on microscopic features using particle size analysis, SEM and TEM and identified mineralogical and textural characteristics to improve our ability to discriminate between the active and inactive gouges. Particle size distribution analysis largely shows that fault gouge in an active fault, having the most abundant finer particles, experienced repetitive shearing whereas the inactive gouges did not. SEM examination of quartz particles shows that more particles retain their primary crystal structure in the active gouge than in the inactive gouges. In contrast, observation of very fine clay minerals using TEM shows the minerals in the active gouge are abraded and corroded in equal or higher degree as the aseismic gouges. Repetitive fault activities could result in the addition of new quartz particles from the granite with preservation of primary crystal structure, whereas relatively-soft clay minerals had been affected by abrasion and dissolution.

JAEA Reports

Materials for the information security education

Yashiro, Shigeo; Aoki, Kazuhisa; Sato, Tomohiko; Tanji, Kazuhiro

JAEA-Review 2013-038, 123 Pages, 2014/01

JAEA-Review-2013-038.pdf:23.19MB

With the rapid progress of the utilization of Information Technology (IT), IT infrastructure (network environment and information system) became crucial as a lifeline for promoting business. At the same time, changes in the circumstances surrounding the IT infrastructure globalize the threat of cyber attacks and increase the risk of the information security such as unlawful access to an information system, viral infection, an alteration of a website, disclosure of subtlety information, destruction of an information system and so on. Information security measure is an important issue in Japan Atomic Energy Agency (JAEA). In order to protect the information property of JAEA from the threat, Center for Computational Science & e-Systems (CCSE) has been taking triadic measures for information security: (1) to lay down a set of information security rules, (2) to introduce security equipments to backbone network and (3) to provide information security education. This report is a summary of the contents of the information security education by e-learning.

Journal Articles

Occurrence and potential activity of denitrifiers and methanogens in groundwater at 140 m depth in Pliocene diatomaceous mudstone of northern Japan

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:8 Percentile:26.35(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 $$^{15}$$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.

Journal Articles

Investigation and research on depth distribution in soil of radionuclides released by the TEPCO Fukushima Dai-ichi Nuclear Power Plant accident

Sato, Haruo; Niizato, Tadafumi; Amano, Kenji; Tanaka, Shingo; Aoki, Kazuhiro

Materials Research Society Symposium Proceedings, Vol.1518, p.277 - 282, 2013/10

The accident of the TEPCO Fukushima Dai-ichi Nuclear Power Plant occurred by the 2011 off the Pacific coast of Tohoku Earthquake on 11 March, 2011. It is estimated that 1.2-1.5$$times$$10$$^{16}$$ Bq for $$^{137}$$Cs and 1.5-1.6$$times$$10$$^{17}$$ Bq for I-131 were released until the beginning of April and those radionuclides (RN) were deposited on soil surface and forest etc. widely around Fukushima Pref. This work was carried out as one of the investigations for making the distribution maps of radiation dose rate and soil contaminated by RNs which the MEXT promotes. The Geoslicer investigation on the depth distribution of RNs in soil was carried out after 3 months from the accident. The investigation was conducted at 11 locations in Nihonmatsu City, Kawamata Town and Namie Town, and soil samples of depth 50 cm to 1 m were taken. Both of $$^{134}$$Cs and $$^{137}$$Cs were detected in all investigated locations, and $$^{rm 129m}$$Te and $$^{rm 110m}$$Ag were detected only in areas where radiation dose rates are high. At many locations investigated, radiocaesium more than 99% distributed within a depth of 10 cm in soil in the surface layer. On the other hand, RNs tended to distribute to deeper part in soil at locations that are supposed to have been used as farmland than in soil in the surface layer, and radiocaesium more than 99% in soil at locations that are supposed to have been used as farmland also distributed within a depth of around 14 cm. The apparent diffusion coefficients of RNs derived from penetration profiles near the surface layer showed a tendency to be higher in soil at locations that are supposed to have been used as farmland than in soil in the surface layer. The distribution coefficients by a batch method were also obtained for Cs and I, and the relationship between D$$_{rm a}$$ and K$$_{rm d}$$ was discussed.

Journal Articles

Impacts of thermo-hydro-mechanical experiments on the microbial activity in compacted bentonite at the Kamaishi Mine, northeast Japan

Aoki, Kazuhiro; Sugita, Yutaka; Chijimatsu, Masakazu*; Tazaki, Kazue*

Applied Clay Science, 47(1-2), p.147 - 154, 2010/01

 Times Cited Count:3 Percentile:13.16(Chemistry, Physical)

Microbial activity has been investigated for the bentonite buffer and surrounding host rock (granodiorite) at Kamaishi Mine in Iwate. For the host rock, total number of bacteria and viable microorganisms were enumerated for deep groundwater in granodiorite. Presence of sulphate-reducing bacteria and denitrifying bacteria were also confirmed. The coupled thermo-hydro-mechanical (T-H-M) experiments named" engineered barrier experiments" were carried out to examine the in situ performance of buffer material. At the end of the heating and cooling phases, bentonite samples were taken for microbial analysis to determine if the naturally present microbial population in the buffer material survived the conditions in a simulated vault environment. The results confirmed the existence of heterotrophs, which disappeared in bentonite samples with low water content. These results suggest that microbial activity is severely limited near waste container in the vault for some time after disposal, due to desiccation as a result of the heat output of the waste container. Such knowledge will be useful in assessing the potential effects of microbial activity on deep geological disposal of high level radioactive waste.

JAEA Reports

Study on investigation of microbial effects for geological disposal, 2 (Joint research)

Tochigi, Yoshikatsu; Yoshikawa, Hideki; Aoki, Kazuhiro; Yui, Mikazu; Asano, Takahiro*; Honjo, Hideko*; Haginuma, Masashi*; Kawakami, Yasushi*; Suzuki, Kazunori*

JAEA-Research 2008-025, 55 Pages, 2008/03

JAEA-Research-2008-025.pdf:8.55MB

Results of joint research on fiscal year 2006 between Japan Atomic Energy Agency (JAEA) and Institute of Research and Innovative (IRI) titled as "Study on investigation of microbial effects for geological disposal" are described in this report. The objective of this study is to develop a method for estimating microbial effects for barrier performance of geological disposal site. The modeling was performed to examine the effect on the change in groundwater chemistry (mainly by electron acceptors) by microbial metabolism as well as microbial activities. In order to use the data (chemical composition, biomass, etc.) in the MINT code, groundwater was collected from the drilled well prepared for chemical and microbial analyses of groundwater. The well was prepared in observation field near Horonobe Underground Research Center of JAEA in fiscal year 2006. Then, numerical modeling using collected data of groundwater with numerical modeling program code "MINT" considering microbial effects was carried out. The modeling was carried out to evaluate the microbial effect for stability of chemical and microbial composition of groundwater. As the result of the modeling, relatively low microbial effect for groundwater composition was observed in particular for the concentration of dissolved methane, methanogen, sulfur reducing bacteria (SRB) and sulfur ion. The result shows that low redox potential is stable in the well in spite of shallow depth.

JAEA Reports

Study on investigation of microbial effects for geological disposal, 1 (Joint research)

Tochigi, Yoshikatsu; Yoshikawa, Hideki; Aoki, Kazuhiro; Yui, Mikazu; Honjo, Hideko*; Haginuma, Masashi*; Kawakami, Yasushi*; Suzuki, Kazunori*

JAEA-Research 2007-010, 51 Pages, 2007/03

JAEA-Research-2007-010.pdf:4.82MB

Results of joint research on Fiscal 2005 between Japan Atomic Energy Agency (JAEA) and Institute of Research and Innovative (IRI) titled as "Study for investigation of microbial effects on geological disposal" are described in this report. The objective of this study is constructing advanced method for examining microbial effect for barrier performance of geological disposal site. In fiscal 2005, groundwater and rock core sample have been collected from drilled well on observation field near Horonobe Underground Research Center of JAEA and chemical analysis for collected ground water have been carried out and sensitivity analysis for existing observed data of groundwater with numerical analysis program code "MINT" considering microbial effect have been carried out.

Journal Articles

Preliminary results of surface-based investigation at the Horonobe url site,Japan

Yamasaki, Shinichi; Fukushima, Tatsuo; Aoki, Kazuhiro

Proceedings of 2nd International Meeting on Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, p.59 - 60, 2005/03

Two off-site Underground Research Laboratory (URL) projects, which are mentioned in the

Journal Articles

Developing a remote monitoring system using ACROSS in Horonobe Underground Research Laboratory

JNC, 1)*; Niizato, Tadafumi; Aoki, Kazuhiro; ;

International workshop on "Active Monitoring in the Solid Earth Geophysics", 0 Pages, 2004/07

Japan Nuclear Cycle Development Institute (JNC) is developing a remote monitoring system using seismic and electromagnetic ACROSS (Accurately Controlled Routinely Operated Signal System) in the Horonobe Underground Research Laboratory (URL). The Horonobe URL project is devoted to the technological development for a safe geological disposal of high level radioactive wastes over a 20-year period from March 2001 in Horonobe-cho in northern Hokkaido, Japan. The purpose of installing a remote monitoring system is to monitor changes in the geological environment before, during and after the construction of an URL facility. The source and receiver system of electromagnetic ACROSS and the receivers of a seismic ACROSS will be installed in the fiscal year 2004, while the source of the seismic ACROSS will be transported from Tono Geoscience Center in 2005.

Journal Articles

Developing a remote monitoring system using ACROSS in the Horonobe Underground Research Laboratory

Tsukui, Rota; Niizato, Tadafumi; Aoki, Kazuhiro; Fukushima, Tatsuo

Proceedings of 1st International Workshop on Active Monitoring in the Solid Earth Geophysics (IWAM 2004), 0 Pages, 2004/07

Japan Nuclear Cycle Development Institute (JNC) is developing a remote monitoring system using seismic and electromagnetic ACROSS (Accurately Controlled Routinely Operated Signal System) in the Horonobe Underground Research Laboratory (URL). Horonobe URL is devoting to the technology development for the safe geological disposal of high level radioactive wastes over 20 years. The project has been operating since March 2001 in Horonobe-cho, northern Hokkaido, Japan. The target of a remote monitoring system is to monitor the change of geological environment before, during and after the construction of the URL underground facility. Receiver system of seismic ACROSS and source and receiver system of electromagnetic ACROSS will be installed in 2004 fiscal year, while source of seismic ACROSS will be transported from Tono Geoscience Center in 2005.

Journal Articles

Influence of bacteria on deep groundwater in relation to geological disposal

Aoki, Kazuhiro

Proceedings of 4th International Symposium on Advanced Science Research (ASR 2004), 0 Pages, 2004/00

Microbial activity can have a significant impact on geochemical processes as it can influence mineral dissolution and precipitation, pH, aokalinity and redox. Laboratory experiments have shown that microbial activity can influence rock-water interactions even in nutrient-poor-conditions.

Journal Articles

None

Kamei, Gento; Ishikawa, Hirohisa; Yui, Mikazu; Uchida, Masahiro; Aoki, Kazuhiro

Saikuru Kiko Giho, (21), p.95 - 98, 2003/12

None

Journal Articles

Underground research laboratories in Japan; What are the important factors for facilities design?

Sato, Toshinori; Mikake, Shinichiro; Sakamaki, Masanori; Aoki, Kazuhiro; Yamasaki, Shinichi; Shigeta, Naotaka; Takeda, Seietsu

9th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM '03), p.1333 - 1339, 2003/00

This paper shows current status of Mizunami Underground Research Laboratory, especially design and construction plan of underground facility.

Journal Articles

Research and development in JNC on geological isolation of high-level radioactive waste in the implementation phase of disposal

Igarashi, Hiroshi; Aoki, Kazuhiro; Miyahara, Kaname; Shiotsuki, Masao; Tachi, Yukio

Nihon Kikai Gakkai Dai-8-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu, p.467 - 472, 2002/06

no abstracts in English

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