The decay products of 229Th (t1/2 = 7932 y), specifically 225Ac (t1/2 = 9.92 d) and 213Bi (t1/2 = 45.61 min), are important alpha-emitting radioisotopes for treating cancer. These radionuclides are in high demand but have a limited supply that includes existing 229Th sources and accelerator-produced 225Ac. To address this shortage, we evaluated a novel method to produce 229Th through the proton irradiation of 230Th (t1/2 = 75,400 y). We first developed a uniformly distributed 230Th target that is optimal for charged particle cross section measurements. The electrophoretic deposition of preformed Th nanoparticles with Ni as the electroactive species was used. Direct electrodeposition of Th is problematic because of the difficulty of reducing Th4+ ions and has led to many researchers attempting the use of aprotic solvents, molten salts, and ionic liquid electrolytes. The codeposited Ni serves a second important function: it will act as an in situ beam monitor through the measurement of the prompt gamma activity of 61Cu (t1/2 = 3.339 h) postirradiation. Using Ce as a cold surrogate for Th, we investigated three Ce-based compositions (e.g., CeO2, CePO4, and CeVO4) to assess which nanoparticle suspension provides the most uniform co-deposition with Ni metal ions. After establishing the electrophoretic deposition of Ce-based nanoparticles, the uniformly deposited 230Th target(s) will be fabricated and irradiated at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. Postirradiation, the target(s) will be processed at Oak Ridge National Laboratory to separate the 229Th decay precursor, 229Pa (t1/2 = 1.5 d), from impurities using ion exchange chromatography methods. After measuring 229Pa yield via gamma ray spectroscopy, we will report the 230Th(p,2n)229Pa reaction cross section.

Thorium-229 production through proton irradiation of thorium-230 nanoparticle-based thin film targets co-deposited with nickel

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.