Quantitative analysis of ionization quenching in CaF:Ce using PHITS track-structure simulations

Hirata, Yuho; Kai, Takeshi; Ogawa, Tatsuhiko; Matsuya, Yusuke; Sato, Tatsuhiko; Watanabe, Kenichi*; Kato, Takumi*; Kawaguchi, Noriaki*; Yanagida, Takayuki*

Radiation Measurements, 193, p.107651_1 - 107651_8, 2026/04

https://doi.org/10.1016/j.radmeas.2026.107651

CaF:Ce has a high potential to be used as a dosimeter due to its high optically stimulated luminescence (OSL) intensity. However, when phosphors such as CaF:Ce are irradiated with swift ions, the OSL intensity per dose decreases due to quenching effects. Traditionally, quenching effects in phosphors have been evaluated based on energy deposition density, using linear energy transfer (LET) as a metric. However, the relationship between quenching effects and LET varies with ion type, complicating unified evaluations. The track structure in PHITS can precisely simulate the radiation interactions. In this study, we simulated the detector response of CaF:Ce irradiated with swift-ions and compared these results with experimental data. The comparison suggests that the quantum yield of OSL is a critical parameter influencing the quenching effect in CaF:Ce. These findings are expected to contribute to the development of improved phosphor detectors.

Measurement and analytical method development of radionuclides in marine products collected off Fukushima coast

Koarai, Kazuma; Matsueda, Makoto; Watanabe, Yusuke; Terashima, Motoki

KEK Proceedings 2025-2 (Internet) , p.151 - 156, 2025/12

https://rcwww.kek.jp/enviconf/information.html

A rapid analytical method was applied to flatfish collected off the coast of Fukushima Prefecture for the determination of tissue free water tritium (TFWT) and OBT in different forms. Quantitative analysis and synchrotron radiation measurements of Re (analogue element of Tc) and stable I in seaweeds were carried out to develop a method for the analysis of Tc-99 and I-129 in seaweeds.

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.

None

Nagata, Shuhei*; Ogawa, Yusuke*; Suzuki, Satoru*; Igarashi, Takahiro; Nagaoka, Toru*; Mitsui, Seiichiro; Watanabe, Yutaka*; Nishikata, Atsushi*

NUMO-TR-25-03, p.46 - 51, 2025/10

no abstracts in English

A Small-scale radiocarbon analysis at JAEA-AMS-TONO

Minamitani, Fumina; Nishio, Tomohiro*; Fujita, Natsuko; Maeta, Yusuke; Miyake, Masayasu; Matsubara, Akihiro*; Uno, Sadanori*; Omae, Akiomi*; Jinno, Satoshi; Watanabe, Takahiro

Dai-25-Kai AMS Shimpojiumu Hokokushu (Internet), 4 Pages, 2025/00

no abstracts in English

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.