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.

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

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

Dai-36-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.90 - 92, 2025/03

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.

Comparison between carrier transport property and crystal quality of TlBr semiconductors

Watanabe, Kenichi*; Sugai, Yusuke*; Hasegawa, Sota*; Tanaka, Seishiro*; Hitomi, Keitaro*; Nogami, Mitsuhiro*; Shinohara, Takenao; Su, Y. H.; Parker, J. D.*; Kockelmann, W.*

Scientific Reports (Internet), 14, p.25224_1 - 25224_13, 2024/10

https://doi.org/10.1038/s41598-024-76005-9

Differential pressure rise event for filters of HTTR primary helium gas circulators, 2; Investigation of filter deposits and recurrence prevention measures

Nemoto, Takahiro; Fujiwara, Yusuke; Arakawa, Ryoki; Choyama, Yuya; Nagasumi, Satoru; Hasegawa, Toshinari; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; et al.

JAEA-Technology 2024-003, 17 Pages, 2024/06

JAEA-Technology-2024-003.pdf:1.91MB

In order to investigate the cause of the increase in differential pressure in the primary helium circulator filter that occurred during the RS-14 cycle, a clogged filter was investigated. As a result of the investigation, deposits caused by silicone oil were confirmed on the surface of the filter element. These results revealed that the cause of filter clogging was silicone oil mixed into the primary system due to performance deterioration of the charcoal filter in the gas circulator of primary helium purification system. As a measure to prevent the recurrence of this event, in addition to the conventional management based on operating hours for replacing of charcoal filter in the gas circulator of primary helium purification system, we have established a new replacement plan for every three years.

Comparison between neutron bragg dip and electron backscatter diffraction images of TlBr semiconductors

Watanabe, Kenichi*; Sugai, Yusuke*; Hasegawa, Sota*; Hitomi, Keitaro*; Nogami, Mitsuhiro*; Shinohara, Takenao; Su, Y. H.; Parker, J. D.*; Kockelmann, W.*

Sensors and Materials, 36(1), p.149 - 154, 2024/01

https://doi.org/10.18494/SAM4629

None

Nagata, Shuhei*; Ogawa, Yusuke*; Suzuki, Satoru*; Inoue, Hiroyuki*; Watanabe, Yutaka*; Yamamoto, Masahiro*; Abe, Hiroshi*; Mitsui, Seiichiro

NUMO-TR-22-02, p.21 - 22, 2023/03

https://www.numo.or.jp/technology/technical_report/NUMO-TR-22-02.pdf

no abstracts in English

A Safer preprocessing system for analyzing dissolved organic radiocarbon in seawater

Otosaka, Shigeyoshi*; Jeon, H.*; Hou, Y.*; Watanabe, Takahiro; Aze, Takahiro*; Miyairi, Yosuke*; Yokoyama, Yusuke*; Ogawa, Hiroshi*

Nuclear Instruments and Methods in Physics Research B, 527, p.1 - 6, 2022/09

https://doi.org/10.1016/j.nimb.2022.07.003

The measurement the radiocarbon of dissolved organic matter (DOC) in seawater can provide information about a timescale of the dynamics of dissolved organic matter as well as about its sources in the ocean. Due to the low DOC concentration in seawater, in spite of the development of accelerator mass spectrometry, a relatively large volume of seawater (1 L) is required for that analysis. In addition, complicated processing such as UV irradiation that emits high heat is required. In this study, we have developed a safer and easier method to analyze DOC in seawater than the conventional method. A particularly significant change was the adoption of a low-pressure mercury lamp in the decomposition system, which enabled direct decomposition of organic matter at lower temperatures. We also propose a method to quantitatively evaluate the accuracy of this system by analyzing simulated seawater consists of a soluble reference material of organic matter and sodium chloride. This method is expected to be applied not only to carbon isotope ratio analysis but also to analysis of trace elements and isotopes of various dissolved organic substances.

Quantitative analyses of major and trace elements in geological samples using a portable energy dispersive X-ray fluorescence spectrometer at Tono Geoscience Center; An Analytical method of whole-rock geochemical composition by 3-mm diameter small spot measurements

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

JAEA-Testing 2021-003, 58 Pages, 2022/01

JAEA-Testing-2021-003.pdf:6.82MB

A long term geosphere stability for geological disposal is evaluated by the past geological environmental changes and modern conditions. Whole-rock geochemical compositions in rocks and sediments are useful information to estimate the past environmental changes and modern conditions. Recently, the portable X-ray fluorescence (XRF) were installed in the Tono Geoscience Center for rapid and simple whole-rock geochemical analyses (original specification; 8 mm-diameter analysis). In particular, the 3 mm-diameter small spot analysis using the portable XRF was performed for quantitative analyses of small-weight geological samples. In this study, we reported a quantitative method for major and trace elements using calibration curves by standard reference materials, as well as evaluation tests of uncertainty by repeated analyses of the standards measured by the portable XRF (3 mm-diameter small spot analysis). Furthermore, the small spot quantitative analyses by the portable XRF were also applied to fault rock samples that have been analyzed in previous studies.

Visualization of radiocesium distribution in surface layer of seafloor around Fukushima Daiichi Nuclear Power Plant

Sanada, Yukihisa; Urabe, Yoshimi*; Misono, Toshiharu; Shiribiki, Takehiko; Nakanishi, Takahiro; Watanabe, Yusuke; Tsuruta, Tadahiko

Scientific Reports (Internet), 11(1), p.23175_1 - 23175_13, 2021/11

https://doi.org/10.1038/s41598-021-02646-9

After the accident at the Fukushima Daiichi Nuclear Power Station (FDNPP) on March 15, 2011, a large amount of volatile radionuclides were released into the atmosphere and hydrosphere. Monitoring of radioactive cesium in sediments is important for assessing the behavior and effects of radioactive cesium in the environment. In this study, the distribution of radioactive cesium in the superficial deposits around FDNPP was visualized as a radioactive cesium map using regular survey data from a towed gamma-ray detection system.

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 circulations

Mitsuguchi, 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

https://doi.org/10.1016/j.jenvrad.2021.106593

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.