Cyclotron production of ²²⁵Ac from an electroplated ²²⁶Ra target

We demonstrate cyclotron production of high-quality ²²⁵Ac using an electroplated ²²⁶Ra target.

²²⁶Ra was extracted from legacy Ra sources using a chelating resin. Subsequent ion-exchange purification gave pure ²²⁶Ra with a certain amount of carrier Ba. The radium target was prepared by electroplating. We successfully deposited about 37 MBq of ²²⁶Ra on a target box. Maximum activation was achieved using 15.6 MeV protons on the target at 20 µA for 5 h. Two functional resins with various concentrations of nitric acid purified ²²⁵Ac and recovered ²²⁶Ra. Cooling the intermediate ²²⁵Ac for 2-3 weeks decayed the major byproduct of ²²⁶Ac and increased the radionuclidic purity of ²²⁵Ac. Repeating the same separation protocol provided high-quality ²²⁵Ac.

We obtained ²²⁵Ac at a yield of about 2.4 MBq at the end of bombardment (EOB), and the subsequent initial purification gave 1.7 MBq of ²²⁵Ac with ²²⁶Ac/²²⁵Ac ratio of < 3% at 4 days from EOB. Additional cooling time coupled with the separation procedure (secondary purification) effectively increased the ²²⁵Ac (4n + 1 series) radionuclidic purity up to 99 + %. The recovered ²²⁵Ac had a similar identification to commercially available ²²⁵Ac originating from a ²²⁹Th/²²⁵Ac generator.

This procedure, which involves the ²²⁶Ra(p,2n)²²⁵Ac reaction and the appropriate purification, has the potential to be a major alternative pathway for ²²⁵Ac production because it can be performed in any facility with a compact cyclotron to address the increasing demand for ²²⁵Ac.