Presentation A feasibility study on 68Ge production from elemental natGa by in-situ extraction process

Nagatsu, Koutarou  ,  Minegishi, Katsuyuki  ,  Ming-Rong, Zhang

Objectives: Germanium-68 (EC, 271 d) is a parent nuclide for 68Ga (+/EC, 68 min), and the systemic elution device called 68Ge/68Ga generators available commercially are widely used. 68Ge can be produced via the 69Ga(p,2n) and 71Ga(p,4n)-channels at a relatively high yield (e.g., 30 Ci+/Ah at 30 MeV+ protons, [1]) though, considerably long irradiation time is needed to obtain a practical yield due to its long half-life. Furthermore, Ga is a low m.p. metal (30oC) and molten Ga shows corrosivity that are regarded as major issues to perform secure irradiation. Thus, we attempted to irradiate an elemental Ga safely and easily by using a vertical irradiation system coupled with a target vessel made of an inert material, silicon carbide (SiC). The 68Ge produced in target Ga was remotely recovered by extraction into a portion of HCl/H2O2 media.Methods: An elemental natGa piece (2.5 g, New Met Koch, UK) was placed in a SiC target vessel. The SiC vessel covered with a 50 m Nb foil was set at a vertical irradiation port. Irradiations were carried out by NIRS AVF-930 cyclotron with 30 MeV protons at 20–23 A for 1–2 h. Then, a portion of 1N-HCl/ 3%-H2O2 (1:1) was introduced into the target vessel, and let the solution go into-and-eject out the vessel repeatedly to stir the molten Ga for about 10 h at 40oC. Subsequently, the crude solution was transferred to hotcell through a Teflon tube (~15 m) by means of N2 pressure. The recovered solution was loaded into a cation exchange resin (AG50W-X8, Bio-Rad) to trap by-produced nuclides and partially dissolved Ga.Results: The extraction of 68Ga was almost quantitative, which was reached to about 94% of total produced. By-produced nuclides found in a crude sample were 67Ga(3.3 d), Ge-69(1.6 d), Zn-65(244 d), and Zn-69m(13.8 h). However, characteristic gammas from 67Ga and 69Ge were good indications to evaluate the behavior of both cold Ga and 68Ge, respectively; and we found that about 3% of target Ga was dissolved into the extract, and the extraction rate of Ge instantly.Conclusion: Although the evaluation of this production system is still challenging, particularly for longer irradiation periods and at higher beam intensities, remote recovery of 68Ge by using a simple method with common solvents was achieved. Acknowledgements: The authors are grateful to the NIRS cyclotron staff for their excellent operation of AVF-930. We also express our gratitude to Dr. Tadashi Nozaki and Dr. Akira Goto for fruitful discussions on the 68Ge/Ga generator, its application, and the visions for educational purpose.References: [1] Adam-Rebels, R. et al. (2013) Radiochim. Acta/ DOI 10.1524/react2013.2057
21st International Symposium on Radiopharmaceutical Sciences

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