Abstract
We propose an innovative way to produce both 225Ac and 227Th, 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 232Th is evaluated by using the TENDL nuclear data. In the photo-transmutation analysis, 13 nuclides including 229Th and 231Pa are modelled. Special procedures with chemical separations are also proposed to produce pure 225Ac and 227Th in separate streams. In addition, performance of the new approach is compared with conventional methods in terms of the 225Ac and 227Th yields. After a Th target is bombarded with a 500 kW electron beam for a year, yearly 225Ac yield is ~ 8.47 GBq (semi-permanently) and yearly 227Th yield is ~ 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.
Highlights
We propose an innovative way to produce both 225Ac and 227Th, two precious radioisotopes enabling promising targeted alpha therapy, in a natural thorium target bombarded with a 30–90 MeV electron beam
The 225Ac supply is rather monopolized and affordable ways are strongly required for progress in the 225Ac-based Targeted alpha (α) therapy (TAT)
In response to the high demand of the ‘rarest drugs’ 225Ac and 227Th, we propose an innovative method to semi-permanently produce the α-emitters with an electron accelerator and natural thorium (232Th) target
Summary
We propose an innovative way to produce both 225Ac and 227Th, two precious radioisotopes enabling promising targeted alpha therapy, in a natural thorium target bombarded with a 30–90 MeV electron beam. Demand for α-emitters has been increasing since the US FDA approved 223Ra chloride as a radiopharmaceutical For cancer treatments, both 225Ac and 227Th are regarded as best α-emitters due to an adequate half-life and emission of multiple α-particles by daughter nuclides. Researches are currently underway to find out alternative methods to produce 225Ac. For example, the Tri-lab project team is looking into ways to directly extract 225Ac from a proton-irradiated thorium target, and produced 81.4 GBq of 225Ac in a 10-day irradiation of 200 MeV proton beam at 165 μA10,11. The Tri-lab project team is looking into ways to directly extract 225Ac from a proton-irradiated thorium target, and produced 81.4 GBq of 225Ac in a 10-day irradiation of 200 MeV proton beam at 165 μA10,11 Regarding this method, one concern is ~ 0.3% yield of 227Ac contaminating 225Ac in addition to the relatively high proton energy required.
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