NRC-8, EuCheMS International Conference on Nuclear and Radiochemistry

INVITED LECTURE - ⁶⁸Ge-⁶⁸Ga production revisited: new excitation functions, target preparation and separation chemistry

19 Sept 2012, 08:30

20m

Como, Italy

Invited Lecture Nuclear Chemistry, Radionuclide Production, High-Power Targetry Session 7 - Nuclear Chemistry, Radionuclide Production, High-Power Targetry

Speaker

Prof. Alex hermanne (Cyclotron lab, Vrije Universiteit Brussel, Belgium)

Description

A. Hermanne¹, R. Adam-Rebeles¹, P. Van den Winkel¹, L. De Vis¹, R. Waegeneer¹, F. Tarkanyi², S. Takacs², M.P. Takacs³. ¹ Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Belgium. ² Institute of Nuclear Research of the Hungarian Academy of Sciences (Atomki), Debrecen, Hungary. ³ Institute of Physics, University of Debrecen, Hungary The use of ⁶⁸Ga (T_1/2= 67.7 m, &beta⁺ decay branching 89.1%) for clinical diagnostic PET imaging is increasing. The fact that it can be obtained from a generator system with long lived ⁶⁸Ge (T_1/2 = 288 d) as parent and its versatile chemistry could make it the PET analogue of the ⁹⁹Mo-^99mTc pair. The preferred route to produce ⁶⁸Ge is intermediate energy proton bombardment of Ga-containing targets. The long half-life however means that long irradiations at high particle flux are needed to produce enough activity for a useful generator (typically 750 MBq). We developed high beam power withstanding targets using electro-deposition of Ga/Ni alloy (70/30%) on industrially used thick Cu backings covered by a 20 μm protective Au layer. Using AC Constant Current Electrolysis (current density 34 mA/cm²) a uniform layer containing 51 mg/cm² Ga is deposited in 7 h from an acid bath containing Ga₂SO₄, NiSO₄ and H₂SO₄. Using thin Ga/Ni targets produced with this technique (6 mg/cm² Ga) we measured cross sections for reactions, induced by protons (up to 65 MeV) and deuterons (up to 50 MeV), producing &gamma-emitting radioisotopes with halflife longer than 2 h. With a stacked foil irradiation, followed by high resolution &gamma-spectrometry, excitation functions for ^68,69Ge, ^66,67,72Ga, ^69m,65Zn were determined, relative to the monitor reaction ^natCu(p or d,x)⁶²Zn. The results are compared to the scarce literature values while from derived thick target yields possibilities to use the deuteron reaction are discussed. A PC-controlled automated set up for delivery of nca ⁶⁹Ge is developed and implemented in an industrial system ready to be mounted in a hot cell. The target layer is dissolved in a mixture of H₂SO₄ and H₂O₂ using a heated,flow trough stripper. Prior to the extraction into toluene, concentrated HCl is added (normality of the solution 0.4 M HCl). The back extraction of the nca ⁶⁸Ge is performed using very diluted HCl. As a last purification step, a cation exchange column is used to adsorb traces of Ga and Ni. Samples are collected for radionuclide and chemical purity analysis. The 40 ml bulk is passed trough a 0.22 μm filter for final filtration-sterilisation. Overall chemistry yield, tested by ⁶⁹Ge tracer, is higher than 90 %.