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Yokoyama, Tatsunori
Isotope News, (764), p.11 - 14, 2019/08
no abstracts in English
Ishimaru, Tsuneari; Ogata, Nobuhisa; Shimada, Akiomi; Asamori, Koichi; Kokubu, Yoko; Niwa, Masakazu; Watanabe, Takahiro; Saiga, Atsushi; Sueoka, Shigeru; Komatsu, Tetsuya; et al.
JAEA-Research 2018-015, 89 Pages, 2019/03
JAEA-Research-2018-015.pdf:14.43MB
This annual report documents the progress of research and development (R&D) in the 3rd 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. In this report, the current status of R&D activities with previous scientific and technological progress is summarized.
Ishimaru, Tsuneari; Ogata, Nobuhisa; Shimada, Akiomi; Asamori, Koichi; Kokubu, Yoko; Niwa, Masakazu; Watanabe, Takahiro; Saiga, Atsushi; Sueoka, Shigeru; Komatsu, Tetsuya; et al.
JAEA-Review 2018-020, 46 Pages, 2019/01
JAEA-Review-2018-020.pdf:1.25MB
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, in fiscal year 2018. The objectives and contents in fiscal year 2018 are described in detail based on the outline of 7 years plan (fiscal years 2015-2021). Background of this research is clarified with the necessity and the significance for site investigation and safety assessment, and the past progress in this report. In addition, 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.
Ishimaru, Tsuneari; Yasue, Kenichi*; Asamori, Koichi; Kokubu, Yoko; Niwa, Masakazu; Watanabe, Takahiro; Yokoyama, Tatsunori; Fujita, Natsuko; Saiga, Atsushi; Shimizu, Mayuko; et al.
JAEA-Research 2018-008, 83 Pages, 2018/12
JAEA-Research-2018-008.pdf:11.43MB
This annual report documents the progress of research and development (R&D) in the 2nd 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. In this paper, the current status of R&D activities with previous scientific and technological progress is summarized.
Yokoyama, Tatsunori; Kimura, Junichi*; Mitsuguchi, Takehiro; Danhara, Toru*; Hirata, Takafumi*; Sakata, Shuhei*; Iwano, Hideki*; Maruyama, Seiji*; Chang, Q.*; Miyazaki, Takashi*; et al.
Geochemical Journal, 52(6), p.531 - 540, 2018/12
Times Cited Count：1 Percentile：52.17(Geochemistry & Geophysics)Ishimaru, Tsuneari; Ogata, Nobuhisa; Shimada, Akiomi; Kokubu, Yoko; Asamori, Koichi; Niwa, Masakazu; Watanabe, Takahiro; Saiga, Atsushi; Sueoka, Shigeru; Yokoyama, Tatsunori; et al.
JAEA-Review 2017-022, 45 Pages, 2017/12
JAEA-Review-2017-022.pdf:1.42MB
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, in fiscal year 2017. The objectives and contents in fiscal year 2017 are described in detail based on the outline of 7 years plan (fiscal years 2015-2021). Background of this research is clarified with the necessity and the significance for site investigation and safety assessment, and the past progress in this report. In addition, 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.
Ishimaru, Tsuneari; Umeda, Koji*; Yasue, Kenichi; Kokubu, Yoko; Niwa, Masakazu; Asamori, Koichi; Watanabe, Takahiro; Yokoyama, Tatsunori; Fujita, Natsuko; Shimizu, Mayuko; et al.
JAEA-Research 2016-023, 91 Pages, 2017/02
JAEA-Research-2016-023.pdf:13.33MB
This annual report documents the progress of research and development (R&D) in the 1st 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. In this paper, the current status of R&D activities with previous scientific and technological progress is summarized.
Yokoyama, Tatsunori; Misawa, Keiji*; Okano, Osamu*; Minowa, Haruka*; Fukuoka, Takaaki*
Journal of Radioanalytical and Nuclear Chemistry, 310(1), p.81 - 89, 2016/10
Times Cited Count：1 Percentile：76.09(Chemistry, Analytical)The identification of alkali-rich components in extraterrestrial materials along with their separation from other constituents is indispensable for subsequent cosmochemical and isotopic studies. This paper presents a simple pre-screening method for such materials by autoradiography using imaging plates (IPs), which is applicable to identification of mm-sized samples containing ca. 30 
g of potassium in the Yamayo-74442 chondrite. The detection limit of IPs was 
1 mBq of 
K under 49 days exposure. The method provides an opportunity to screen meteorite materials non-destructively and to inexpensively check potassium-rich areas and suitable for the K-Ca and K-Ar (
Ar-Ar) age determinations.
Ishimaru, Tsuneari; Yasue, Kenichi; Kokubu, Yoko; Niwa, Masakazu; Asamori, Koichi; Watanabe, Takahiro; Yokoyama, Tatsunori; Fujita, Natsuko; Shimizu, Mayuko; Hama, Yuki
JAEA-Review 2016-016, 44 Pages, 2016/08
JAEA-Review-2016-016.pdf:2.28MB
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 JAEA, in fiscal year 2016. The objectives and contents in fiscal year 2016 are described in detail based on the outline of 7 years plan (fiscal years 2015-2021). Background of this research is clarified with the necessity and the significance for site investigation and safety assessment, and the past progress in this report. In addition, 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.
Umeda, Koji; Yasue, Kenichi; Kokubu, Yoko; Niwa, Masakazu; Asamori, Koichi; Fujita, Natsuko; Shimizu, Mayuko; Matsubara, Akihiro; Tamura, Hajimu; Yokoyama, Tatsunori; et al.
JAEA-Review 2015-019, 42 Pages, 2015/09
JAEA-Review-2015-019.pdf:4.64MB
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 JAEA, in fiscal year 2015. The objectives and contents in fiscal year 2015 are described in detail based on the outline of 7 years plan (fiscal years 2015-2021). Background of this research is clarified with the necessity and the significance for site investigation and safety assessment, and the past progress in this report. In addition, 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.
Umeda, Koji; Yasue, Kenichi; Kokubu, Yoko; Niwa, Masakazu; Asamori, Koichi; Fujita, Natsuko; Shimizu, Mayuko; Shimada, Akiomi; Matsubara, Akihiro; Tamura, Hajimu; et al.
JAEA-Review 2015-012, 43 Pages, 2015/08
JAEA-Review-2015-012.pdf:1.24MB
The concept of geological disposal of high-level radioactive waste (HLW) in Japan is based on a multibarrier system which combines a stable geological environment with an engineered barrier system. Potential geological host formations and their surroundings are chosen, in particular, for their long-term stability, taking into account the fact that Japan is located in tectonically active zone. This report is to outline 7 years plan (fiscal years 2015-2021) of research and development (R&D) for geosphere stability for long-term isolation of the HLW in JAEA. Background of this research is clarified with the necessity and the significance, and the past progress in this report. The objectives, outline, contents and schedule during the next 7 years are described in detail. In addition, 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.
Fujita, Natsuko; Matsubara, Akihiro; Kokubu, Yoko; Niwa, Masakazu; Tamura, Hajimu; Shibata, Kenji; Yokoyama, Tatsunori
no journal, ,
no abstracts in English
Yokoyama, Tatsunori; Kokubu, Yoko; Murakami, Hiroaki; Hirata, Takafumi*; Sakata, Shuhei*; Danhara, Toru*; Iwano, Hideki*; Chang, Q.*; Kimura, Junichi*
no journal, ,
The chronological information about carbonates is useful for modeling and enables forecast of geological and geochemical environmental changes by simulating. The U-Th-Pb dating method for carbonates which were formed at reducing environment remain to be established. The final goal of our study is to establish in situ U-Th-Pb dating method for carbonates which are filling cracks in pervious rock like fault rocks. In this study, the U-Th-Pb elemental and isotopic two-dimension distribution for an ammonite fossil were visualized by "Imaging" method using Laser-ablation ICP Mass Spectrometry. In U-Pb isotope analysis for carbonates in cracks of granites, we could not obtain significant U-Pb age data by the lack of uranium and influence of non-radiogenic common lead. When the concentration of lead is sufficiently high for the measurement, we obtained reliable isotopic data from carbonates and their lead isotopic composition reflected characteristic composition of their origin water.
Watanabe, Takahiro; Kokubu, Yoko; Murakami, Hiroaki; Yokoyama, Tatsunori; Amamiya, Hiroki; Mizuno, Takashi; Kubota, Mitsuru; Iwatsuki, Teruki
no journal, ,
Chronological and geochemical studies of fracture filling calcite in rocks provide the information for changes in geochemical condition, such as redox potential and pH in geological environments. Because the calcite can be found as common filling minerals in the natural samples, age zoning and spatial distribution of chemical composition in the calcite could be a wide-use indicator to reconstruct the past environmental changes. Radiometric (U-Pb) dating in a micro scale area (less than 10 micrometer) on the filling mineral surface by laser ablation-inductively coupled plasm mass spectrometry system (LA-ICPMS) has been applied to geological samples. Additionally, past redox potential has been estimated by Fe contents in the carbonates, which is based on the distribution coefficient of Fe between calcite deposit and groundwater. In this study, we evaluated the possibility of in-situ radiometric dating for the filling minerals by LA-ICPMS and redox potential reconstruction by the theoretical calculation using the distribution coefficient.
Yokoyama, Tatsunori; Kokubu, Yoko; Murakami, Hiroaki; Watanabe, Takahiro; Hirata, Takafumi*; Sakata, Shuhei*; Danhara, Toru*; Iwano, Hideki*; Maruyama, Seiji*; Miyazaki, Takashi*; et al.
no journal, ,
Chronological and geochemical studies of carbonates, which are commonly found as fracture filling minerals in rocks, can provide information about geochemical conditions present during formation including in deep subsurface environments. A dating technique for the carbonates using laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS) is still immature partly because of a lack of a consensus international carbonate standard for the in-situ dating technique. In this study, we performed a survey on the carbonate standard materials that may be suitable for high precision U-Th-Pb dating using LA-MC-ICPMS. We examined carbonate standard materials JCp-1 and JCt-1 issued by the Geological Survey of Japan (GSJ). Based on solution-based bulk analysis using MC-ICP-MS, heterogeneities in Pb isotope compositions were confirmed. Nevertheless, the 206Pb-based isotopic compositions were all within 1.2 per mill variations acceptable for a standard used for age determination using LA-MC-ICPMS. Additional tests on the heterogenities in U-Th-Pb compositions of the carbonate standards along with determinations of other trace elements using a 2D imaging LA-ICP-MS are ongoing. Examinations on both natural standards and synthetic standards are ongoing for further efforts in determination of the standard suitable for U-Th-Pb dating of carbonates.
Murakami, Hiroaki; Kokubu, Yoko; Yokoyama, Tatsunori; Watanabe, Takahiro; Yuguchi, Takashi*; Fujikawa, Masayuki*; Nishiyama, Tadao*
no journal, ,
In order to observe micro-growth layers in carbonate, we consider availability and measurement procedure of cathodoluminescence for various carbonates. Optical-CL image and SEM-CL image provide layering structures of entire area and microscale distribution of layering structures, respectively. Thus, the approach in the order of Optical-CL measurement to SEM-CL measurement is powerful means of microscale observation of carbonate.
Yokoyama, Tatsunori; Kokubu, Yoko; Murakami, Hiroaki; Watanabe, Takahiro; Mitsuguchi, Takehiro
no journal, ,
no abstracts in English
Yokoyama, Tatsunori; Kokubu, Yoko; Mitsuguchi, Takehiro; Murakami, Hiroaki; Hirata, Takafumi*; Sakata, Shuhei*; Danhara, Toru*; Iwano, Hideki*; Maruyama, Seiji*; Chang, Q.*; et al.
no journal, ,
no abstracts in English
Yokoyama, Tatsunori
no journal, ,
no abstracts in English
Yokoyama, Tatsunori; Kokubu, Yoko; Mitsuguchi, Takehiro; Murakami, Hiroaki; Hirata, Takafumi*; Sakata, Shuhei*; Danhara, Toru*; Iwano, Hideki*; Maruyama, Seiji*; Miyazaki, Takashi*; et al.
no journal, ,
Chronological and geochemical studies of calcium carbonates can provide precious information for changes in geochemical condition in deep geological environments. Because the carbonate can be found as common filling minerals in rocks, age zoning and spatial distribution of chemical composition in the carbonate could be a wide-use indicator to reconstruct the past environmental changes. Calcite and other carbonate materials have been dated by Isotope Dilution-Thermal Ionization Mass Spectrometry. On the other hand, a few of U-Pb dating studies in a micro scale area (less than 10 micrometer) such as using laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS) has been conducted on the carbonate. The U-Pb dating technique for the carbonates using LA-MC-ICPMS is still immature partly because of a lack of consensus international carbonate reference materials for the in-situ dating technique. In order to solve this problem, we performed a survey on the carbonate reference materials that may be suitable for high precision U-Pb dating using LA-MC-ICPMS. Additionally, we conducted experiments to make compositionally homogeneous carbonate (calcite) reference materials.
