Reactor method streamlines production of medical copper isotope Cu 64

by Robert Schreiber
Berlin, Germany (SPX) Dec 05, 2025

The copper isotope Cu-64 is an important tool in nuclear medicine for imaging applications and is also being explored for cancer treatment, but it does not occur naturally and must be produced in dedicated facilities. Cu-64 has 29 protons and 35 neutrons, making it radioactive with a half-life of about 13 hours, which is long enough for transport and imaging but short enough to limit patient radiation exposure.

Until now, Cu-64 has typically been produced in cyclotrons by bombarding enriched nickel-64 with protons so that the nickel nucleus captures a proton, emits a neutron, and transforms into copper-64. Veronika Rosecker of TU Wien explains that this cyclotron-based method is effective but costly, and it also depends on access to enriched Ni-64, which is a scarce isotope.

A research team at TU Wien has now demonstrated an alternative pathway that converts stable copper-63 directly into copper-64 using neutron irradiation in a research reactor. In this process, Cu-63 nuclei capture neutrons in the reactor to form Cu-64, but this initially led to a mixture dominated by ordinary copper atoms with only small amounts of Cu-64, which could not be separated by standard chemical methods. Martin Pressler notes that direct irradiation of bulk copper produces the desired isotope but leaves it chemically indistinguishable from the surrounding copper.

The TU Wien group addressed this challenge with recoil chemistry, a concept known for almost a century but not previously applied to the production of medical radioisotopes. Before irradiation, copper atoms are incorporated into specially designed molecules so that when a Cu-63 atom absorbs a neutron and becomes Cu-64, it carries excess energy that is released as gamma radiation. "When a Cu-63 atom within such a molecule absorbs a neutron and becomes Cu-64, it briefly holds a large amount of excess energy, which it releases as gamma radiation," says Veronika Rosecker. The emission of the high-energy photon imparts a recoil to the atom, comparable to a rocket reaction, strong enough to eject the newly formed Cu-64 from the molecule.

"This means that Cu-63 and Cu-64 can now be cleanly separated," says Veronika Rosecker. "The Cu-63 atoms remain bound within the molecules, while the newly formed Cu-64 atoms are released. This makes it easy to separate the two isotopes chemically." In practice, the Cu-63 atoms stay in the intact complexes, while ejected Cu-64 ions can be collected and purified, yielding samples with high molar activity suitable for radiopharmaceutical use.

A critical step in the project was to identify molecular complexes that meet the demands of a reactor environment and downstream processing. The team used a metal-organic complex that resembles heme, the iron-containing molecule in human blood, providing a robust ligand framework for binding copper. Pressler explains that earlier related complexes lacked solubility, so the TU Wien researchers modified the chemistry to create a soluble complex, allowing efficient recovery and processing of Cu-64 after irradiation.

According to the team, the new method can be automated, the carrier molecules can be reused without loss of function, and production uses a research reactor instead of a cyclotron. This approach could lower barriers for facilities that already operate research reactors and need reliable access to Cu-64 for diagnostic imaging and potential therapeutic studies.

Research Report:Fast and easy reactor-based production of copper-64 with high molar activities using recoil chemistry