Design of a thorium metal target for 225Ac production at TRIUMF




Robertson, Andrew K. H.
Lobbezoo, Andrew
Moskven, Louis
Schaffer, Paul
Hoehr, Cornelia

Journal Title

Journal ISSN

Volume Title




With recent impressive clinical results of targeted alpha therapy using 225Ac, significant effort has been directed towards providing a reliable and sufficient supply of 225Ac to enable widespread using of 225Ac-radiopharmaceuticals. TRIUMF has begun production of 225Ac via spallation of thorium metal with 480 MeV protons. As part of this program, a new 225Ac-production target system capable of withstanding the power deposited by the proton beam was designed and its performance simulated over a range of potential operating parameters. Special attention was given to heat transfer and stresses within the target components. The target was successfully tested in two irradiations with a 72–73 μA proton beam for a duration of 36.5 h. The decay corrected activity at end of irradiation (average ± standard deviation) was (524 ± 21) MBq (14.2 mCi) and (86 ± 13) MBq (2.3 mCi) for 225Ac and 225Ra, respectively. These correspond to saturation yields of 72.5 MBq/μA for 225Ac and 17.6 MBq/μA for 225Ra. Longer irradiations and production scale-up are planned in the future.



actinium-225, thorium, spallation, proton target, ANSYS, targeted alpha therapy


Robertson, A. K. H., Lobbezoo, A., Moskven, L., Schaeffer, P., & Hoehr, C. (2019). “Design of a thorium metal target for 225Ac production at TRIUMF.” Instruments, 3(1), 18.