Simulation study of medical isotope production by accelerator induced reactions

This paper presents a simulation studies on the production of precious medical isotopes²²⁵Ac, ^223,225Ra,^227,229Th and ⁹⁹Mo via α -induced reactions on ²³²Th using the PHITS code. Bombarding a Th target with energetic α-particles, a secondary high-energy mixed radiation field—comprising neutrons and protons—is generated, enabling the efficient production of multiple isotopes applicable in nuclear medicine as radiopharmaceuticals for diagnostic or therapeutic purposes. Firstly, the production cross-sections of these isotopes induced by α-particles, neutrons, protons, tritons, etc., on the ²³²Th target were simulated, with projectile energies ranging from 20 to 250 MeV/nucleon. Subsequently, a simplified accelerator-driven subcritical blanket (ADSB) system model was presented. This model primarily comprises a water-cooled spallation target (composed of ²³²Th + D₂O) and a surrounding blanket (made of Th), the yield distributions in different regions of the system, as well as the various nuclear reaction pathways to isotope yields were quantified. Thereafter, the energy deposition in the metal thorium target and the water-cooled target, along with the isotope yields, were compared. Finally, the secondary particle flux distributions and isotope yields induced by different accelerated charged particles in the ADSB system were also analyzed.