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Journal Articles

Dating of geological samples

Kokubu, Yoko

ISEE Newsletter, 9, P. 4, 2020/01

no abstracts in English

Journal Articles

Seismic subsidence near the source region of the 1662 Kanbun Hyuganada Sea earthquake: Geochemical, stratigraphical, chronological, and paleontological evidences in Miyazaki Plain, southwest Japan

Niwa, Masakazu; Kamataki, Takanobu*; Kurosawa, Hideki*; Kokubu, Yoko; Ikuta, Masafumi*

Island Arc, 29(1), p.e12341_1 - e12341_26, 2020/01

Based on detailed geochemical and paleontological analyses for lowland sediments in the Miyazaki Plain, southwest Japan, we clearly identified environmental change from the lower terrestrial sediments to the upper shallow marine sediments. Radiocarbon ages and tephra data suggest that the environmental change is attributed to local subsidence due to the 1662 Kanbun Hyuganada Sea Earthquake shown in historical records. This findings are important for historical earthquake studies because the study area is a part of the expected focal region of megathrust earthquakes along the Nankai Trough.

Journal Articles

Radiocarbon dating of a shrine pavilion and offerings at Abushina shrine in Gifu prefecture, Japan

Kokubu, Yoko; Nishio, Tomohiro; Fujita, Natsuko; Matsubara, Akihiro

Proceedings of the 8th East Asia Accelerator Mass Spectrometry Symposium and the 22nd Japan Accelerator Mass Spectrometry symposium (EA-AMS 8 & JAMS-22), p.91 - 93, 2020/00

no abstracts in English

Journal Articles

Present status of the JAEA-AMS-TONO in 2019

Fujita, Natsuko; Matsubara, Akihiro; Miyake, Masayasu*; Watanabe, Takahiro; Kokubu, Yoko; Kato, Motohisa*; Okabe, Nobuaki*; Isozaki, Nobuhiro*; Ishizaka, Chika*; Nishio, Tomohiro; et al.

Proceedings of the 8th East Asia Accelerator Mass Spectrometry Symposium and the 22nd Japan Accelerator Mass Spectrometry symposium (EA-AMS 8 & JAMS-22), p.34 - 36, 2020/00

no abstracts in English

Journal Articles

Lahar record during the last 2500 years, Chokai Volcano, northeast Japan; Flow behavior, sourced volcanic activity, and hazard implications

Minami, Yusuke*; Oba, Tsukasa*; Hayashi, Shintaro*; Kokubu, Yoko; Kataoka, Kyoko S.*

Journal of Volcanology and Geothermal Research, 387, p.106661_1 - 106661_17, 2019/12

 Times Cited Count:0 Percentile:100(Geosciences, Multidisciplinary)

The study focuses on volcanic-fan deposits at Chokai Volcano in northeast Japan. The authors conducted sedimentary facies analysis, radiocarbon dating, and historical document analysis to understand the flow characteristics and history of far-reaching lahars. The volcanic fan is composed mainly of a series of lahar deposits formed by at least five large lahar events at: the 2nd - 5th century BC; 2nd to 4th century BC; AD 5th to 7th century; AD 871; and AD 1801 during last 2500 years. These lahar events can be classified into three types: (1) a cohesive debris flow sourced by the debris avalanche deposit; (2) a non-cohesive lahar by a magmatic eruption; and (3) a cohesive debris flow by a phreatic eruption. The lahar, incorporating debris avalanche deposit, flowed as hazardous cohesive debris flow; lahars after magmatic eruptions tends to be streamflow through the flow transformation of sandy debris flow; and a cohesive lahar by a phreatic eruption tends to be of small scale.

Journal Articles

A Suitable procedure for preparing of water samples used in radiocarbon intercomparison

Takahashi, Hiroshi*; Minami, Masayo*; Aramaki, Takafumi*; Handa, Hiroko*; Kokubu, Yoko; Ito, Shigeru*; Kumamoto, Yuichiro*

Radiocarbon, 61(6), p.1879 - 1887, 2019/12

 Times Cited Count:0 Percentile:100(Geochemistry & Geophysics)

Water sample for interlaboratory comparison (here after "comparison water") must have inalterable $$^{14}$$C concentration during the comparison campaign and inter-batches homogeneity. In this study, the procedure for preparing of comparison water was discussed. We employed that comparison waters were artificially made by mixing chemical reagents, controlling $$^{14}$$C concentration and chemical composition. We could prepare six comparison waters, having 1, 14, 37, 56, 72 and 100 pMC, respectively. The stable carbon isotopic values and chemical compositions of some batches were measured to exanimate the inter- batches homogeneity. The $$^{14}$$C discrepancies among the batches were negligible for the inter-laboratory comparison. Finally, the results of trial comparison in Japan will be presented. Most of $$^{14}$$C results of CO$$_{2}$$ extracted by six laboratories showed good agreements each other.

JAEA Reports

Sample preparation method for measurement of in-situ belliyum-10 and allumium-26 in terrestrial quartz using accelerator mass spectrometry at Tono Geoscience Center, Japan Atomic Energy Agency

Kokubu, Yoko; Matsushi, Yuki*; Ishizaka, Chika*; Hirao, Noriaki*; Yonaga, Yusuke; Yoshikawa, Kiyotaka*

JAEA-Testing 2019-002, 101 Pages, 2019/11

JAEA-Testing-2019-002.pdf:4.69MB

This report provides a description of sample preparation method for measurement of in-situ belliyum-10 ($$^{10}$$Be) and allumium-26 ($$^{26}$$Al) in terrestrial quartz using accelerator mass spectrometry at Tono Geoscience Center, Japan Atomic Energy Agency. The report is based on the laboratory manual "Chemistry for in-situ $$^{10}$$Be and $$^{26}$$Al measurement for terrestrial quartz by AMS at MALT ver.1.3 and ver.2.2" prepared by ph.D Matsushi at Kyoto University.

JAEA Reports

Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal year 2018

Ishimaru, Tsuneari; Ogata, Nobuhisa; Hanamuro, Takahiro; Shimada, Akiomi; Kokubu, Yoko; Asamori, Koichi; Niwa, Masakazu; Shimada, Koji; Watanabe, Takahiro; Saiga, Atsushi; et al.

JAEA-Research 2019-006, 66 Pages, 2019/11

JAEA-Research-2019-006.pdf:4.39MB

This annual report documents the progress of research and development (R&D) in the 4th 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.

Journal Articles

Current status of JAEA-AMS-TONO in the 20th year

Kokubu, Yoko; Fujita, Natsuko; Miyake, Masayasu; Watanabe, Takahiro; Ishizaka, Chika; Okabe, Nobuaki; Ishimaru, Tsuneari; Matsubara, Akihiro*; Nishizawa, Akimitsu*; Nishio, Tomohiro*; et al.

Nuclear Instruments and Methods in Physics Research B, 456, p.271 - 275, 2019/10

 Times Cited Count:0 Percentile:100(Instruments & Instrumentation)

JAEA-AMS-TONO has been in operation at the Tono Geoscience Center, Japan Atomic Energy Agency since 1998 and 20 years have passed from the beginning of its utilization. The AMS system is a versatile system based on a 5 MV tandem Pelletron type accelerator. The system has been used to measure carbon-14 ($$^{14}$$C), beryllium-10 ($$^{10}$$Be) and aluminium-26 ($$^{26}$$Al). In addition, the development of measurement of iodine-129 ($$^{129}$$I) has been started. The main use is measurement of $$^{14}$$C in geological samples for dating studies in neotectonics and hydrogeology. In order to increase the speed of sample preparation, we introduced the automated graphitization equipment and made a gas-strip line to collect dissolved inorganic carbon in groundwater samples. Measurement of $$^{10}$$Be and $$^{26}$$Al has been used for geoscience studies and the detection limit in the measurement of $$^{10}$$Be was improved by $$^{7}$$Be-counting suppression. Recently tuning of measurement condition of $$^{129}$$I has been progressed.

Journal Articles

Preliminary test of the EA-AGE3 system for $$^{14}$$C measurement of CaCO$$_{3}$$ samples and coral-based estimation of marine reservoir correction in the Ogasawara Islands, Northwestern Subtropical Pacific

Kokubu, Yoko; Mitsuguchi, Takehiro*; Watanabe, Takahiro; Yamada, Tsutomu*; Asami, Ryuji*; Iryu, Yasufumi*

Radiocarbon, 61(5), p.1593 - 1601, 2019/10

 Times Cited Count:0 Percentile:100(Geochemistry & Geophysics)

We performed $$^{14}$$C measurements of two fossil and one modern corals using a combined system of an elemental analyzer and an automated graphitization equipment AGE3 (EA-AGE3 system) and JAEA-AMS-TONO. The $$^{14}$$C concentrations (pMC values) of mid-Holocene Okinawa corals obtained by our EA-AGE3 system appear to be slightly higher than those obtained by the conventional graphitization method using phosphoric acid. The pMC increase in our EA-AGE3 system may result in significant underestimation of $$^{14}$$C age especially for older samples (e.g., 10,000 BP); however, the pMC increase is negligible in $$^{14}$$C measurements of modern or recent samples. We applied the EA-AGE3 method to the pre- and post-bomb annual-band samples from the modern Ogasawara coral for $$^{14}$$C measurements. On the basis of the pre-bomb coral $$^{14}$$C data, we estimated marine reservoir correction ($$Delta$$R) around Ogasawara Islands and its stability between $$sim$$1900 and 1950 AD.

JAEA Reports

Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific program for fiscal year 2019)

Ishimaru, Tsuneari; Ogata, Nobuhisa; Hanamuro, Takahiro; Shimada, Akiomi; Kokubu, Yoko; Asamori, Koichi; Niwa, Masakazu; Shimada, Koji; Watanabe, Takahiro; Sueoka, Shigeru; et al.

JAEA-Review 2019-010, 46 Pages, 2019/09

JAEA-Review-2019-010.pdf:2.45MB

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 2019. The objectives and contents in fiscal year 2019 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.

Journal Articles

Nagasaki sediments reveal that long-term fate of plutonium is controlled by select organic matter moieties

Lin, P.*; Xu, C.*; Kaplan, D. I.*; Chen, H.*; Yeager, C. M.*; Xing, W.*; Sun, L.*; Schwehr, K. A.*; Yamazaki, Hideo*; Kokubu, Yoko; et al.

Science of the Total Environment, 678, p.409 - 418, 2019/08

 Times Cited Count:0 Percentile:100(Environmental Sciences)

Nagasaki sediments containing bomb-derived Pu provided a unique opportunity to explore the long term geochemical behavior of Pu. Through a combination of selective extractions and molecular characterization via electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry, we determined that 55 $$pm$$ 3% of the $$^{239,240}$$Pu was preferentially associated with more persistent organic matter compounds in Nagasaki sediments, particularly those natural organic matter (NOM) stabilized by Fe oxides. Other organic matter compounds served as a secondary sink of these $$^{239,240}$$Pu (31 $$pm$$ 2% on average), and less than 20% of the $$^{239,240}$$Pu was immobilized by inorganic mineral particles. While present long-term disposal and environmental remediation modeling assume that solubility limits and sorption to mineral surfaces control Pu subsurface mobility, our observations suggest that NOM undoubtedly plays an important role in sequestering Pu. Ignoring the role of NOM in controlling Pu fate and transport is not justified in most environmental systems.

Journal Articles

$$^{14}$$C ages and calendar years of Japanese nails measured with accelerator mass spectrometry

Nagata, Kazahiro*; Furunushi, Yasuko*; Matsubara, Akihiro*; Kokubu, Yoko; Nakamura, Toshio*

Tetsu To Hagane, 105(4), p.488 - 491, 2019/04

 Times Cited Count:0 Percentile:100(Metallurgy & Metallurgical Engineering)

The Japanese nails had been produced by the traditional ironmaking way of Tatara until the Edo period since the late of 6 Century. The quality of the Japanese nails is affected from steel produced by Tatara in each age. The $$^{14}$$C ages of 3 Japanese nails collected at shrines and temples at their repair were measured with accelerator mass spectrometry and calibrated to calendar years. Each $$^{14}$$C age provided plural calendar year periods with definite probabilities, and one of the periods determined in comparison with the history of temples and their repair records. The production ages of nails used in the Daibutuden of the Todaiji temple, the living quarters of the Manjuin temple and the Zaoudo of the Yoshino-Kongoji temple are before 1692, the 12 Century and before 1592, respectively, when they were repaired or reconstructed.

JAEA Reports

Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal year 2017

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.

JAEA Reports

Proceedings of the 30th Meeting for Tandem Accelerators and their Associated Technologies

Ishimaru, Tsuneari; Shimada, Akiomi; Kokubu, Yoko; Fujita, Natsuko

JAEA-Conf 2018-003, 147 Pages, 2019/02

JAEA-Conf-2018-003.pdf:58.99MB

The 30th Meeting of Tandem Accelerators and their Associated Technologies was held on July 6 and 7, 2017 at Tono Geoscience Center of the Japan Atomic Energy Agency. This meeting involved the participation of 97 persons from universities, research institutes and companies which have tandem accelerators and/or electrostatic accelerators. The purpose of the meeting is to contribute to research and development of accelerator technology through exchange of information among the engineers and the researchers who are interested in a tandem accelerator or an electrostatic accelerator. The meeting consisted of oral and poster sessions, and there were 33 presentations which contained about the current status of tandem accelerator facilities, technical developments and research using accelerators, etc. This proceedings summarizes the contents of the presentations at the meeting.

JAEA Reports

Proceedings of the 20th Japanese Symposium on Accelerator Mass Spectrometry

Ishimaru, Tsuneari; Shimada, Akiomi; Kokubu, Yoko; Fujita, Natsuko; Watanabe, Takahiro

JAEA-Conf 2018-002, 134 Pages, 2019/02

JAEA-Conf-2018-002.pdf:15.31MB

This proceedings issue includes the presentation contents of the 20th Japanese Symposium on Accelerator Mass Spectrometry (JAMS-20). The JAMS-20 was held by Tono Geoscience Center, Japan Atomic Energy Agency, on December 14-15th, 2017. The number of participants was seventy five during two days. On the Symposium, thirty two presentations were made for facility status reports, analytical developments and application techniques.

Journal Articles

The present status of the AGE3 automated graphitization equipment for radiocarbon dating at the JAEA-AMS-TONO

Watanabe, Takahiro; Kokubu, Yoko; Fujita, Natsuko; Ishizaka, Chika*; Nishio, Tomohiro; Matsubara, Akihiro*; Miyake, Masayasu; Kato, Motohisa*; Isozaki, Nobuhiro*; Torazawa, Hitoshi*; et al.

JAEA-Conf 2018-002, p.116 - 119, 2019/02

AMS is widely used for radiocarbon dating of geological samples. However, improvement in efficiency of sample preparation techniques are needed for high-time resolution dataset. In 2016, automated graphitization equipment (AGE3, IonPlus AG) has been installed in Toki Research Institute of Isotope Geology and Geochronology, Tono Geoscience Center, JAEA. Background values and carbon recovery rates during preparation process of AGE3 should be estimated before application in radiocarbon dating. In this study, the AGE3 system was evaluated using the international standard materials (IAEA-C1, C4, C5, C6, C7, C9 and NIST-SRM4990C) at JAEA-AMS-TONO. Graphite samples was prepared by the AGE3 system and radiocarbon concentration of these standards was measured by AMS. The results were agreement with the consensus values. Background values were 0.15$$pm$$0.01 pMC (IAEA-C1) using the AGE3 system. Therefore, we concluded that the system can be adapted for radiocarbon dating of geological samples.

Journal Articles

Improvement of methods for measurement of $$^{129}$$I/$$^{127}$$I ratio at JAEA-AMS-TONO

Okabe, Nobuaki; Fujita, Natsuko; Matsubara, Akihiro*; Miyake, Masayasu; Nishio, Tomohiro*; Nishizawa, Akimitsu*; Isozaki, Nobuhiro*; Watanabe, Takahiro; Kokubu, Yoko

JAEA-Conf 2018-002, p.51 - 54, 2019/02

no abstracts in English

Journal Articles

The Twenty years of JAEA-AMS-TONO

Kokubu, Yoko; Fujita, Natsuko; Matsubara, Akihiro*; Nishizawa, Akimitsu*; Nishio, Tomohiro; Miyake, Masayasu; Ishimaru, Tsuneari; Watanabe, Takahiro; Ogata, Nobuhisa; Shimada, Akiomi; et al.

JAEA-Conf 2018-002, p.5 - 8, 2019/02

no abstracts in English

Journal Articles

Preliminary results of $$^{10}$$Be of the rock samples from the lake terrace of the Lake Pumayum Co in Tibetan Plateau

Nara, Fumiko*; Watanabe, Takahiro; Kokubu, Yoko; Horiuchi, Kazuho*

JAEA-Conf 2018-002, p.124 - 127, 2019/02

In-situ cosmogenic radionuclides have been used to understand earth surface processes, such as the erosion rate and exposure age dating of rocks. This is a preliminary report on in-situ $$^{10}$$Be values measurements by Accelerator Mass Spectrometry (AMS) for rock samples from the shore of the Lake Pumoyum Co in Tibetan plateau. The $$^{10}$$Be concentrations ranged from 5.5-7.5$$times$$10$$^{6}$$ atom/g similar to those of the surface sediments of Lake Pumoyum Co. The calculated erosion rates were 5.2-7.6 mm/kyr, values close to those previously reported by Lal et al. (2003).

219 (Records 1-20 displayed on this page)