2019 Fiscal Year Final Research Report

Development of Accelerator Mass Spectrometry for Ultrasensitive Detection of Multi Long-lived Radionuclides

Research Project

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Project/Area Number	15H02340
Research Category	Grant-in-Aid for Scientific Research (A)
Allocation Type	Single-year Grants
Section	一般
Research Field	Nuclear engineering
Research Institution	University of Tsukuba
Principal Investigator	Sasa Kimikazu 筑波大学, 数理物質系, 准教授 (20312796)
Co-Investigator(Kenkyū-buntansha)	末木啓介筑波大学, 数理物質系, 教授 (90187609) 坂口綾筑波大学, 数理物質系, 准教授 (00526254) 松崎浩之東京大学, 総合研究博物館, 教授 (60313194) 國分陽子国立研究開発法人日本原子力研究開発機構, 核燃料・バックエンド研究開発部門東濃地科学センター, 研究副主幹 (10354870) 松四雄騎京都大学, 防災研究所, 准教授 (90596438) 松村宏大学共同利用機関法人高エネルギー加速器研究機構, 放射線科学センター, 准教授 (30328661) 松中哲也金沢大学, 環日本海域環境研究センター, 助教 (60731966)
Project Period (FY)	2015-04-01 – 2019-03-31
Keywords	加速器質量分析 / 長寿命放射性核種 / 環境動態研究 / 同位体トレーサー / 同位体分析 / 放射線物理 / 量子ビーム
Outline of Final Research Achievements	A multi-nuclide accelerator mass spectrometry system was developed at the University of Tsukuba. The particle detection system was designed for high-sensitivity detection of Be-10, C-14, Al-26, Cl-36 and I-129 in isotopic-ratio ranges from 10E-10 to 10E-15. We developed the sulfur removal method to reduce S-36 contamination for Cl-36 AMS. AgCl samples were pressed into an AgBr backing in a large Cu sample cathode.The system background for Cl-36 measurements has a Cl-36/Cl ratio of < 3 × 10E-15. Ca-41 and Sr-90 were also successfully detected with the multi-nuclide AMS system. AMS performance is entirely satisfactory for analysis of cosmogenic nuclides in environmental research. Cl-36 and I-129 were measured most frequently in order to investigate the radioactive contamination in rainwater and soil samples, caused by the Fukushima Daiichi Nuclear Power Plant accident. Be-10 and Cl-36 were applied for the tracer of cosmic ray events in the ice core and variations of solar activity.
Free Research Field	加速器質量分析
Academic Significance and Societal Importance of the Research Achievements	大型の加速器質量分析装置により、同位体比10E-10 から10E-15レベルの環境中の極微量核種が検出可能となった。特に炭素14（C-14)以外のBe-10, Al-26, Cl-36, Ca-41，Sr-90, I-129などの長寿命放射性核種について、同位体トレーサーとして環境動態研究に適用することが可能となった。今後、地球環境科学などの自然科学分野や原子力分野などにおいて、応用研究の進展が期待できる。