Annual report for research on geosphere stability for long-term isolation of radioactive waste in fiscal year 2024

Asamori, Koichi; Sueoka, Shigeru; Kobayashi, Tomoharu; Nishiyama, Nariaki; Tanaka, Kiriha; Murakami, Osamu; Fukuda, Shoma; Ogata, Manabu; Uchida, Mao; Komatsu, Tetsuya; et al.

JAEA-Research 2025-007, 99 Pages, 2025/10

JAEA-Research-2025-007.pdf:12.36MB

This annual report documents the progress of research and development (R&D) in the 3rd fiscal year of the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028) to provide the scientific base for assessing geosphere stability for long-term isolation of high-level radioactive waste. 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. The current status of R&D activities with previous scientific and technological progress is summarized.

Linking combustion-derived magnetite and black carbon; Insights from magnetic characterization of PM in downwind East Asia

Nozomu, Tsuchiya*; Ikemori, Fumikazu*; Kawasaki, Kazuo*; Yamada, Rena*; Hata, Mitsuhiko*; Furuuchi, Masami*; Iwamoto, Yoko*; Kaneyasu, Naoki*; Sadanaga, Yasuhiro*; Watanabe, Takahiro; et al.

Environmental Science & Technology, 59(21), p.10400 - 10410, 2025/05

https://doi.org/10.1021/acs.est.4c14187

Black carbon (BC) is a typical primary aerosol emitted from combustion. While its co-existence with iron oxides (FeO) has recently been reported, the extent of bias caused by FeO mixing to the BC observations is largely unknown. To identify the dominant FeO emission sources and associated overestimation of BC, magnetics properties of PM collected at a remote site in East Asia was investigated in combination with detailed isotopic and chemical analyses. Consequently, biomass burning events did not enhance aerosol magnetism as they did for the mass concentration of BC, whereas coal burning events coincided with periods of high magnetization. Therefore, magnetization/BC ratio is proposed as a highly selective indicator for identifying combustion sources (i.e. coal, oil or biomass burning).

Alternative radiocarbon age-depth model from Lake Baikal sediment; Implication for past hydrological changes for last glacial to the Holocene

Nara, Fumiko*; Watanabe, Takahiro; Lougheed, B.*; Obrochta, S.*

Radiocarbon, 66(6), p.1940 - 1957, 2024/12

https://doi.org/10.1017/RDC.2023.63

We present an updated radiocarbon age model using IntCal20 to calibrated new AMS data applied to a Lake Baikal sediment core in south Siberia. Radiocarbon measurements showed that the core extends to 32 cal kaBP. To take into account uncertainties in radiocarbon age and sedimentation depth in the core, a new age-depth modeling routine, undatable, was used in this study. Undatable revealed that the significant changes in the sedimentation rate correspond to global climate events, either warm or cold, which are the Meltwater pulses (MWP) at 19 and 14 cal kaBP and the Last glacial maximum (LGM) at 21-20 cal kaBP. Since the Selenga River accounts for 50 % of the total river inflow to Lake Baikal, we interpret that these changes in sedimentation rate could be signals of significant increase in Selenga River discharge to the lake, which is expected to be affected by global climate change.

Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific program for fiscal year 2024)

Niwa, Masakazu; Shimada, Akiomi; Asamori, Koichi; Sueoka, Shigeru; Komatsu, Tetsuya; Nakajima, Toru; Ogata, Manabu; Uchida, Mao; Nishiyama, Nariaki; Tanaka, Kiriha; et al.

JAEA-Review 2024-035, 29 Pages, 2024/09

JAEA-Review-2024-035.pdf:1.24MB

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 (JAEA), in fiscal year 2024. The objectives and contents of this research are described in detail based on the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. 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.

Present status of the JAEA-AMS-TONO (2023FY)

Fujita, Natsuko; Miyake, Masayasu; Matsubara, Akihiro*; Ishii, Masahiro*; Takahashi, Yuto*; Watanabe, Takahiro; Jinno, Satoshi; Nishio, Tomohiro*; Ogawa, Yumi; Kimura, Kenji; et al.

Dai-25-Kai AMS Shimpojiumu Hokokushu (Internet), 3 Pages, 2024/03

The JAEA-AMS-TONO facility at the Tono Geoscience Center, JAEA has three accelerator mass spectrometers. We report the present status of the JAEA-AMS-TONO.

Stable hydrogen and oxygen isotope analyses of geological samples using a thermal conversion elemental analyzer-isotope ratio mass spectrometer at Tono Geoscience Center

Yamamoto, Yusuke*; Watanabe, Takahiro; Niwa, Masakazu; Shimada, Koji

JAEA-Testing 2023-003, 67 Pages, 2024/02

JAEA-Testing-2023-003.pdf:4.63MB

A long-term geosphere stability for geological disposal is evaluated by the past geological environmental changes and modern conditions. Stable hydrogen and oxygen isotope ratios (D, O) of geological samples are useful information to estimate the past environmental changes and modern conditions. Recently, the thermal conversion elemental analyzer and isotope ratio mass spectrometer (TC-EA/IRMS) were installed in the Tono Geoscience Center for D and O measurements of geological samples. In this study, we reported analytical methods of D and O using international standard reference materials. In addition, evaluation tests of uncertainty by repeated analyses of the standards were performed using the TC-EA/IRMS. Furthermore, the D and O analyses by the TC- EA/IRMS were also applied to fault rock samples.

Simple and rapid method for geochemically discriminating of paleotsunami deposits using a portable X-ray fluorescence spectrometry system; Application to boring cores from the Shizuoka plain on the Pacific coast of central Japan

Watanabe, Takahiro; Yamamoto, Yusuke; Kitamura, Akihisa*

Chigaku Zasshi, 132(5), p.417 - 437, 2023/10

https://doi.org/10.5026/jgeography.132.417

To improve a geochemical discrimination method of paleotsunami deposit, quantitative analysis of major and trace elements in boring cores from the Shizuoka plain on the Pacific coast of middle Japan was performed using a portable energy dispersive X-ray fluorescence spectrometry system (portable XRF). Geochemical approaches by the portable XRF contribute to study of the simple and rapid methods for detecting paleotsunami deposits. Most of our quantitative data by portable XRF were good agreement with reported values measured by stationary-type energy dispersive XRF in previous studies. Therefore, the portable XRF can be applied to geochemical study in the samples from Shizuoka plain in our case.

Status report of JAEA-AMS-TONO; Research and technical development in the last four years

Kokubu, Yoko; Fujita, Natsuko; Watanabe, Takahiro; Matsubara, Akihiro; Ishizaka, Chika; Miyake, Masayasu*; Nishio, Tomohiro*; Kato, Motohisa*; Ogawa, Yumi*; Ishii, Masahiro*; et al.

Nuclear Instruments and Methods in Physics Research B, 539, p.68 - 72, 2023/06

https://doi.org/10.1016/j.nimb.2023.03.005

The JAEA-AMS-TONO facility at the Tono Geoscience Center, JAEA has an accelerator mass spectrometer (JAEA-AMS-TONO-5MV). The spectrometer enabled us to use a multi-nuclide AMS of carbon-14 (C), beryllium-10, aluminium-26 and iodine-129, and we have recently been proceeding test measurement of chlorine-36. In response to an increase of samples, we installed a state-of-the-art multi-nuclide AMS with a 300 kV Tandetron accelerator in 2020. Recently, we are driving the development of techniques of isobar separation in AMS and of sample preparation. Ion channeling is applied to remove isobaric interference and we are building a prototype AMS based on this technique for downsizing of AMS. The small sample graphitization for C has been attempted using an automated graphitization equipment equipped with an elemental analyzer.

Present status of the JAEA-AMS-TONO (2021)

Matsubara, Akihiro*; Fujita, Natsuko; Miyake, Masayasu; Ishii, Masahiro*; Watanabe, Takahiro; Kokubu, Yoko; Nishio, Tomohiro*; Ogawa, Yumi; Jinno, Satoshi; Kimura, Kenji; et al.

JAEA-Conf 2022-002, p.55 - 62, 2023/03

https://doi.org/10.11484/jaea-conf-2022-002

We report the present status of the JAEA-AMS-TONO. Particularly, the destructions of varistors used in the beamline equipment will be presented. The cause of the destruction as well as implementation of the safety measures are mentioned.

Research plan on geosphere stability for long-term isolation of radioactive waste (Scientific program for fiscal year 2022)

Sasao, Eiji; Ishimaru, Tsuneari; Niwa, Masakazu; Shimada, Akiomi; Shimada, Koji; Watanabe, Takahiro; Sueoka, Shigeru; Yokoyama, Tatsunori; Fujita, Natsuko; Ogita, Yasuhiro; et al.

JAEA-Review 2022-022, 29 Pages, 2022/09

JAEA-Review-2022-022.pdf:0.97MB

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 (JAEA), in fiscal year 2022. The objectives and contents in fiscal year 2022 are described in detail based on the JAEA 4th Medium- and Long-term Plan (fiscal years 2022-2028). In addition, the background of this research is described from the necessity and the significance for site investigation and safety assessment, and the past progress. 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