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Mitsuguchi, Takehiro; Okabe, Nobuaki*; Kokubu, Yoko; Matsuzaki, Hiroyuki*
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 31(2), p.96 - 110, 2024/12
Geological disposal of high-level radioactive waste requires not only selecting sites appropriate for the waste repository, where its isolation ability would not be damaged by natural phenomena for several tens of thousands of years, but also rationally constructing the disposal system depending on site-specific geological environments and their anticipated long-term variability. Recently, elemental/isotopic compositions of underground fluids (deep groundwaters, hot/cold spring waters, brines associated with oil and natural gas reservoirs, and so on) in Japan have been studied for evaluating the long-term stability of the geological environments of this country. Iodine and its radioactive isotope 
I (half-life = 15.7 million years) are included in the subjects of the study. The current review paper provides overviews of (i) the iodine content and iodine-129/127 ratio (I/
I ratio) of various materials in Earth's surface layers, (ii) relevant sample pretreatments and measurements, and (iii) I/I data of the underground fluids in Japan, then gives (iv) some interpretations of the fluid I/I data, along with their problems and uncertainties, and (v) some implications towards evaluating the long-term stability of geological environments.
I/I and 
C records in a modern coral from Rowley Shoals off northwestern Australia reflect the 20th-century human nuclear activities and ocean/atmosphere circulationsMitsuguchi, Takehiro; Okabe, Nobuaki*; Yokoyama, Yusuke*; Yoneda, Minoru*; Shibata, Yasuyuki*; Fujita, Natsuko; Watanabe, Takahiro; Kokubu, Yoko
Journal of Environmental Radioactivity, 235-236, p.106593_1 - 106593_10, 2021/09
Times Cited Count：5 Percentile：22.85(Environmental Sciences)For a contribution to developing the usage of iodine-129 (I) as a tracer of deep-seated fluid, I/I and C were measured for annual bands (AD 1931-1991) of a modern coral collected from Northwestern Australia; the measurements were performed using the JAEA-AMS-TONO-5MV for I/I and an AMS facility of the University of Tokyo for C. Results indicate that both I/I and C distinctly increase from 1950s. The C increase can be ascribed to atmospheric nuclear tests, while the I/I increase is due to nuclear-fuel reprocessing as well as atmospheric nuclear tests. These results are in good agreement with previous studies, indicating that the I/I measurement by JAEA-AMS-TONO-5MV has been further developed.
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
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：6 Percentile：48.20(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 (C), beryllium-10 (
Be) and aluminium-26 (
Al). In addition, the development of measurement of iodine-129 (I) has been started. The main use is measurement of 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 Be and Al has been used for geoscience studies and the detection limit in the measurement of Be was improved by 
Be-counting suppression. Recently tuning of measurement condition of I has been progressed.
Fujita, Natsuko; Matsubara, Akihiro; Miyake, Masayasu*; Watanabe, Takahiro; Kokubu, Yoko; Kato, Motohisa*; Okabe, Nobuaki*; Isozaki, Nobuhiro*; Ishizaka, Chika*; Torazawa, Hitoshi*; et al.
Dai-32-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.57 - 59, 2019/09
no abstracts in English
I/I ratio at JAEA-AMS-TONOOkabe, 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
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
Fujita, Natsuko; Miyake, Masayasu; Watanabe, Takahiro; Kokubu, Yoko; Matsubara, Akihiro*; Kato, Motohisa*; Okabe, Nobuaki; Isozaki, Nobuhiro*; Ishizaka, Chika*; Torazawa, Hitoshi*; et al.
Dai-31-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.92 - 95, 2018/12
no abstracts in English
I/I ratio and present status of JAEA-AMS-TONOOkabe, Nobuaki; Fujita, Natsuko; Watanabe, Takahiro; Kokubu, Yoko
no journal, ,
no abstracts in English
I/I measurement at the JAEA-AMS-TONOMiyake, Masayasu; Fujita, Natsuko; Okabe, Nobuaki; Kokubu, Yoko; Shimada, Akiomi; Ogata, Nobuhisa
no journal, ,
no abstracts in English
Fujita, Natsuko; Matsubara, Akihiro; Miyake, Masayasu*; Okabe, Nobuaki*; Nishio, Tomohiro*; Kimura, Kenji; Watanabe, Takahiro; Kokubu, Yoko
no journal, ,
no abstracts in English
Mitsuguchi, Takehiro; Okabe, Nobuaki*; Kokubu, Yoko; Matsuzaki, Hiroyuki*
no journal, ,
no abstracts in English
I/I ratio in underground water by accelerator mass spectrometry at Tono Geoscience Center, Japan Atomic Energy AgencyFujita, Natsuko; Okabe, Nobuaki*; Matsubara, Akihiro; Miyake, Masayasu*; Kokubu, Yoko; Watanabe, Takahiro
no journal, ,
no abstracts in English
Fujita, Natsuko; Matsubara, Akihiro; Miyake, Masayasu*; Watanabe, Takahiro; Kokubu, Yoko; Kato, Motohisa*; Okabe, Nobuaki*; Isozaki, Nobuhiro*; Ishizaka, Chika*; Nishio, Tomohiro; et al.
no journal, ,
no abstracts in English
I measurement of CaCO
samples in JAEA-AMS-TONOMitsuguchi, Takehiro; Okabe, Nobuaki*; Miyake, Masayasu*; Matsubara, Akihiro; Fujita, Natsuko; Watanabe, Takahiro; Kokubu, Yoko
no journal, ,
A preliminary test for AMS I measurement of CaCO samples was performed using a tandem Pelletron AMS system at Tono Geoscience Center, Japan Atomic Energy Agency (JAEA-AMS-TONO). An annually-banded coral collected from Vietnam was used for this test. The procedure of the test was as follows: (1) an annual-band sample of AD 1946-47 from the coral was treated with 1% HCl for removal of its surface portion; (2) the treated sample was dissolved in HPO
solution; (3) an aliquot from the sample solution was used for I measurement by ICP-MS; (4) the Woodward iodine standard was added as a carrier to the sample solution; (5) iodine was extracted from the solution by solvent extraction and back-extraction, resulting in an aqueous phase with extracted iodine; (6) AgNO(aq) was added to the aqueous phase to obtain AgI precipitate; (7) the AgI precipitate was mixed with Nb and pressed into a copper cathode for I measurement by JAEA-AMS-TONO. A blank test of this procedure was also made to evaluate the background I effect in the sample preparation. Results we obtained were as follows: (1) the background I/I ratio was [4.3 
0.1] 
10
and (2) the background-corrected coral I/I ratio was [1.53 0.76] 10
. The coral I/I ratio is generally in agreement with previously-reported values of Chang et al. (2016), suggesting that AMS I measurement of CaCO samples has been generally established in JAEA-AMS-TONO.
I/I measurement at the JAEA-AMS-TONOFujita, Natsuko; Okabe, Nobuaki; Matsubara, Akihiro*; Miyake, Masayasu; Nishio, Tomohiro*; Nishizawa, Akimitsu*; Isozaki, Nobuhiro*; Watanabe, Takahiro; Kokubu, Yoko
no journal, ,
no abstracts in English
