Feasibility of producing 225 Ac via thermal neutron irradiation of 226 Ra: A systematic theoretical study

With a suitable half-life and abundant radiolabeling strategy, 225 Ac has become one of the most promising radionuclides in the area of targeted alpha therapy. However, limited radionuclide supply is threatening the development of 225 Ac related endoradiotherapy dramatically. As the parent nuclide of 225 Ac, 229 Th can be produced via 226 Ra(3n, 2β) 229 Th reaction in a nuclear reactor. However, related practice has not been conducted in large scale, since the nuclear reaction pathway for producing 229 Th is complicated. In this work, the feasibility of producing 225 Ac/ 229 Th in a reactor was confirmed by systematic theoretical calculations, and a procedure that combines irradiation with separation process was proposed. The results show that 176 MBq of 229 Th can be produced by irradiating 1.0 g of 226 Ra with a neutron flux density of 1 × 10 15 n cm −2 s −1 for 90 days. This will generate 150 MBq of 225 Ac monthly from a radionuclide generator, which is sufficient for the single treatment cycle of 200 patients each year considering the radioactivity loss in radiochemical separation, transfer and radiolabeling process. In addition, this irradiation process will also produce 37.8 GBq 227 Ac for the preparation of 227 Ac- 227 Th- 223 Ra generator. In general, the production of 225 Ac by neutron irradiation of 226 Ra in reactor is practicable and holds potential to alleviate the shortage of current supply of 225 Ac.