Feasibility of a novel photoproduction of Ac-225 and Th-227 with natural thorium target

Abstract

We propose an innovative way to produce both Ac-225 and Th-227, two precious radioisotopes enabling promising targeted alpha therapy, in a natural thorium target bombarded with a 30-90 MeV electron beam. Bremsstrahlung photons in the target are analyzed by MCNP and in-situ photonuclear transmutation of Th-232 is evaluated by using the TENDL nuclear data. In the photo-transmutation analysis, 13 nuclides including Th-229 and Pa-231 are modelled. Special procedures with chemical separations are also proposed to produce pure Ac-225 and Th-227 in separate streams. In addition, performance of the new approach is compared with conventional methods in terms of the Ac-225 and Th-227 yields. After a Th target is bombarded with a 500 kW electron beam for a year, yearly Ac-225 yield is similar to 8.47 GBq (semi-permanently) and yearly Th-227 yield is similar to 48.9 GBq over 50 years, and their yields are at least doubled in a 2-year irradiation. This work will help increase global supply of the two precious isotopes and would invariably help advance TAT-related researches and developments.