A theoretical model for the production of Ac-225 for cancer therapy by neutron capture transmutation of Ra-226

Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. We are investigating the reduction of radium by transmutation by bombarding Ra-226 with high-energy neutrons from a neutron source to produce Ra-225 and hence Ac-225, which can be used as a generator to produce Bi-213 for use in ‘Targeted Alpha Therapy’ for cancer.This paper examines the possibility of producing Ac-225 by neutron capture using a theoretical model in which neutron energy is convoluted with the corresponding neutron cross sections of Ra-226. The total integrated yield can then be obtained.This study shows that an intense beam of high-energy neutrons could initiate neutron capture on Ra-226 to produce Ra-225 and hence practical amounts of Ac-225 and a useful reduction of Ra-226.

► Ra-226 was irradiated with reactor neutrons in simulations.
► Ra-225 yields were calculated for neutron energies between 8 MeV and 12.5 MeV.
► Fast Breeder reactors supply a greater neutron flux at higher energies.
► Commercial quantities of Ra-225 could be produced from grams of Ra-226 in days.