Radium-223 derived from proton irradiated Thorium is the first alpha-emitting isotope that obtained Food and Drug Administration approval for the treatment of cancer. 2I3Bismuth is a decay product of 225Ac (t1/2 = 10.0 d), itself an alpha emitter. Currently the domestically-produced supply of 225Ac, however, is limited by the availability of the parent radionuclide, 229Th, derived from U233, all of which is currently being destroyed by down blending.
Oak Ridge National Lab: High Flux Isotope Reactor
References:
- https://www.energy.gov/science/np/articles/thorium-source-multiple-medical-isotopes
- https://pubs.acs.org/doi/abs/10.1021/bk-2004-0868.ch013
