論文

論文出版：²¹¹Rn/²¹¹Atジェネレータ開発のための励起関数測定

Measurements of the excitation functions of radonand astatine isotopes from ⁷Li-induced reactions with ²⁰⁹Bi for development of a ²¹¹Rn-²¹¹At generator

Eita Maeda, Akihiko Yokoyama, Takumi Taniguchi, Kohshin Washiyama, Ichiro Nishinaka

J. Radioanal. Nucl. Chem. 323, 921 (2020).

We have measured excitation functions of ²⁰⁹Bi(⁷Li, 5n)²¹¹Rn, ²⁰⁹Bi(⁷Li, 6n)²¹⁰Rn, and other reactions, with the aim of realizing a ²¹¹Rn/²¹¹At generator for cancer therapy. On the basis of a comparison with theoretical predictions, we found that nuclides of ²¹⁰At are produced via a break-up process rather than from the ²⁰⁹Bi(⁷Li, p5n)²¹⁰At reaction. The excitation functions obtained in this study provide the most favorable conditions for ²¹¹Rn production in terms of available radioactivity and nuclide purity of the irradiated material.

論文出版：ポリエチレン遮へい中での特異的なRI生成反応

Anomalous radioisotope production for ⁶⁸ZnO using polyethylene by accelerator neutrons

Kazuaki Tsukada, Yasuki Nagai, Shintaro Hashimoto, Futoshi Minato, Masako Kawabata, Yuichi Hatsukawa, Kazuyuki Hashimoto, Satoshi Watanabe, Hideya Saeki, and Shoji Motoishi

J. Phys. Soc. Jpn. 89, 034201 (2020).

We measured the yields of radionuclides after neutron irradiation on an enriched ⁶⁸ZnO sample covered with polyethylene blocks. The neutrons were generated from the ⁹Be(d,n) reaction by 40 and 50 MeV deuterons. For 50 MeV deuterons we observed anomalously enhanced yields of ⁶⁷Ga, ⁶⁶Ga, ^69mZn, and ⁶⁴Cu, more than 20-times larger than the yields for a ⁶⁸ZnO sample without the polyethylene blocks. At the same time, the yields of the same radioisotopes produced from an enriched metallic ⁶⁸Zn sample were almost insensitive to the presence of polyethylene. On the other hand, for 40 MeV deuterons the enhanced production was not observed. This finding would provide a unique capability of accelerator neutrons to simultaneously produce large amounts of several radioisotopes via neutron-induced reactions on a single sample. The experimental data are compared with the yields calculated by the simulation code Particle and Heavy Ion Transport code System (PHITS). The calculated yields of these radioisotopes produced from the ⁶⁸ZnO sample covered with the polyethylene blocks considerably disagree with the measured ones, while for the ⁶⁸ZnO sample without the blocks they agree with each other.

論文出版：酸化・還元剤とアスタチン（²¹¹At）の反応：溶存・揮発性アスタチン化学種の同定

Speciation of astatine reacted with oxidizing and reducing reagents by thin layer chromatography: formation of volatile astatine

Ichiro Nishinaka, Kazuyuki Hashimoto, Hiroyuki Suzuki

J. Radioanal. Nucl. Chem. 322, 2003 (2019).

Radio-chromatography was conducted by using the astatine radionuclides ^{209, 210, 211}At produced in the ⁷Li induced reaction of ²⁰⁹Bi. The speciation of dissolved astatine chemical species of astatide (At⁻), astatate (AtO₃⁻) and perastatate (AtO₄⁻) was carried out by thin layer chromatography on silica gel with an ethanol/water solution. Amounts of the astatine species varied with concentrations of oxidizing and reducing reagents, potassium periodate, sodium sulfate and hydrazine hydrate. The oxidation–reduction reactions between At⁻ (−I) and AtO₃⁻ (V) were found to form volatile At⁰ (0) and release it from a silica gel thin layer in the development.

論文出版：⁹⁹Mo生成量評価

⁹⁹Mo yield using large sample mass of MoO₃ for sustainable production of ⁹⁹Mo

Kazuaki Tsukada, Yasuki Nagai, Kazuyuki Hashimoto, Masako Kawabata, Futoshi Minato, Hideya Saeki, Shoji Motoishi and Masatoshi Itoh

J. Phys. Soc. Jpn. 87, 043201 (2018).

A neutron source from the C(d,n) reaction has the unique capability of producing medical radioisotopes such as ⁹⁹Mo with a minimum level of radioactive waste. Precise data on the neutron flux are crucial to determine the best conditions for obtaining the maximum yield of ⁹⁹Mo. The measured yield of ⁹⁹Mo produced by the ¹⁰⁰Mo(n,2n)⁹⁹Mo reaction from a large sample mass of MoO₃ agrees well with the numerical result estimated with the latest neutron data, which are a factor of two larger than the other existing data. This result establishes an important finding for the domestic production of ⁹⁹Mo: approximately 50% of the demand for ⁹⁹Mo in Japan could be met using a 100 g ¹⁰⁰MoO₃ sample mass with a single accelerator of 40 MeV, 2 mA deuteron beams.

論文出版：²¹¹At溶存化学種の解明

Thin layer chromatography for astatine and iodine in solution prepared by dry distillation

Ichiro Nishinaka, Kazuyuki Hashimoto, Hiroyuki Suzuki

J. Radioanal. Nucl. Chem. 318, 897 (2018).

The astatine radionuclides ^{208,209,210,211}At and the iodine radionuclides 1^20,122,123I were simultaneously produced by ⁷Li beam irradiation of a stack of lead and tin targets. The astatine and the iodine radionuclides each were separated from the irradiated target with a dry distillation method. No-carrier-added astatine and iodine solutions were prepared using ethanol or water as a solvent. Astatine in the aqueous solution was reacted with an oxidizing or a reducing agent. Separation of the astatine and the iodine ions in the solutions was conducted by thin layer chromatography on silica gel with an ethanol/water solution. Astatine was separated and identified as anions of At^-, AtO₃^- and AtO₄^-, while iodine was I^-, compared with the standard iodine species.

論文出版：^95mTcのコンプトンカメラ撮像実験

Electron tracking Compton camera imaging of technetium-95m

Yuichi Hatsukawa, Takehito Hayakawa, Kazuaki Tsukada, Kazuyuki Hashimoto, Tetsuya Sato, Masato Asai, Atsushi Toyoshima, Toru Tanimori, Shinya Sonoda, Shigeto Kabuki, Hiroyuki Kimura, Atsushi Takada, Tetsuya Mizumoto, Seiya Takaki

PLoS ONE, 13(12): e0208909 (2018).

Imaging was conducted using an electron tracking Compton camera (ETCC), which measures γ-rays with energies in the range of 200-900 keV from ^95mTc. ^95mTc was produced by the ⁹⁵Mo(p, n)^95mTc reaction on a ⁹⁵Mo-enriched target. A method for recycling ⁹⁵Mo-enriched molybdenum trioxide was employed, and the recycled yield of ⁹⁵Mo was 70-90%. Images were obtained with the gate of three energies. The results showed that the spatial resolution increases with increasing γ-ray energy. This suggested that the ETCC with high-energy γ-ray emitters such as ^95mTc is useful for medical imaging of deep tissue and organs in the human body.