Production of high purity ⁹⁷Tc for environmental research

Abstract

A procedure for the preparation of a pure ⁹⁷Tc isotope that can be used as a tracer in dilution mass spectrometry and accelerator mass spectrometry is described. The reaction ⁹⁵Mo (⁴He, 2n) ⁹⁷Ru was used. An enriched ⁹⁵Mo(>90%) target (10 mg cm⁻²) was irradiated with 31.5 MeV ⁴He-ions for 70 h at 30 μA. The obtained ⁹⁷Ru decayed (T_1/2=2.9 d) to form ⁹⁷Tc (99.9%) and ^97mTc (1.7×10⁻²%). After cooling for 100 days the target was removed from the copper backing. The radiochemical procedure included dissolution of the target and two-fold distillation of ⁹⁷Tc as Tc₂O₇ with HClO₄. Over 98% of ⁹⁷Tc was recovered after two distillations. The radioactive admixtures of ^56,57,58Co, ⁵⁴Mn, ⁶⁵Zn produced from the copper backing were quantitatively retained in the precipitate in a distillation still. The obtained quantity of ⁹⁷Tc was 3.5 μg. According to the calculation it contained less than 0.1% of ⁹⁷Mo.