RIKEN Accel. Prog. Rep. 50 (2017)

Ⅲ-3. Radiochemistry & Nuclear Chemistry

Development of a production technology of 211 At at the RIKEN AVF
cyclotron: (i) Production of 211 At from the 209 Bi(α,2n)211 At reaction
N. Sato,∗1 S. Yano,∗1 A. Toyoshima,∗1,∗2,∗3 H. Haba,∗1 Y. Komori,∗1 S. Shibata,∗1 K. Watanabe,∗1 D. Kaji,∗1K. Takahashi,∗1 and M. Matsumoto∗4∗1
∗2
∗3
∗4

RIKEN Nishina Center
Advanced Science Research Center, Japan Atomic Energy
AgencyGraduate School of Science, Osaka Univ.
Japan Radioisotope Association- 262 -Fig. 1. (a) Schematic view of the irradiation system. (b)Photograph of the 211 At production chamber. (c)Vacuum-evaporated Bi target on an Al plate (after irradiation).
Thick target yield (GBq/C)

Astatine-211 (211 At, T1/2 = 7.214 h) is one of thepromising radionuclides for the α-particle therapy ofdiseases. The 5.9- and 7.5-MeV α-particle emissions
occur with intensities of 42% and 58%, respectively,
associated with the 211 At decay.1) Owing to the proper
ranges of these α-particles in tissue (60–80 μm), the211
At-labeled medicine is eﬀective in killing focus cells.
For the pre-clinical and clinical trials, a large amountof 211 At-labeled compounds is needed.
We have started to produce 211 At from the209
Bi(α,2n)211 At reaction at the RIKEN AVF cyclotron and to distribute it to researchers in universities and institutes in Japan. Figure 1 shows the irradiation system for the 211 At production. An 18-μm
beryllium window was placed to separate the vacuum
beam line and the He-ﬁlled 211 At production chamber.
A metallic 209 Bi target (chemical purity: >99.999%,
typical thickness: 20 mg/cm2 ) was prepared by vacuum evaporation onto an Al backing plate of 1-mmthickness. The Bi target was placed at an angle of 15◦
with respect to the beam axis. A 29.36-MeV α beam
was delivered from the AVF cyclotron; the beam energy on the center of the target surface was calculated
to be 28.4 MeV with the SRIM-2013 program.2) To
obtain 211 At with a high radionuclidic purity, the αbeam energy was controlled at 28–29 MeV to preventthe production of 210 At (T1/2 = 8.1 h), which decays
to a highly toxic α emitter 210 Po (T1/2 = 138 d); thethreshold energy for the 209 Bi(α,3n)210 At reaction is28.6 MeV. Thus, electrostatic pickups were used for an
accurate evaluation of the beam energy.3) The target
was cooled with circulating water (1.5 L/min) and He
gas (30 L/min) during the irradiation. A beam wobbler system was used to rotate the beam spot on thetarget and to prevent heat concentration. The Bi targets were irradiated for 20–30 min at beam intensities
between 1 and 10 particle μA. After the irradiation,
the targets were subjected to γ-ray spectrometry witha Ge detector.
Figure 2 shows the thick-target yield of 211 At as afunction of the α-beam energy on the target. Our
experimental data almost agree with the IAEA recommended values.4) The deduced yield of 211 At was
7.2 ± 0.5 GBq/C at 28.4 MeV, which was nearly constant upto 10 particle μA. According to this work,

15This work
Qaim ('11)
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Alpha-beam energy on target (MeV)

Fig. 2. Thick target yield of 211 At as a function of α-beamenergy. The solid curve indicates the IAEA recommended value.4)

about 500 MBq of 211 At could be obtained under 10particle μA irradiation for 1 h. The atomic ratio of210
At/211 At at the end of bombardment (EOB) wasestimated to be < 1×10−5 , which satisﬁed the medical
requirement of < 1 × 10−3 at EOB.5) After the irradiation, 211 At was puriﬁed by a dry distillation method,which is reported in our succeeding paper.6)
References
1) R. B. Firestone et al.: Table of Isotopes CD-ROM, 8thed. (John Wiley and Sons, New York, 1998).
2) J. F. Ziegler et al.: Nucl. Instrum. Meth. Phys. Res. B
268, 1818 (2010).
3) T. Watanabe et al.: Proc. 12th Annual Meeting of Particle Accelerator Society of Japan (2015), p. 1198.
4) S. M. Qaim et al. (eds.): IAEA Technical Report Series
No. 473, IAEA, Vienna, Austria (2011).
5) A. Hermanne et al.: Appl. Radiat. Isot. 63, 1 (2005).
6) S. Yano et al.: In this report.