%0 Journal Article
%T Actinium-225 photonuclear production in nuclear reactors using a mixed radium-226 and gadolinium-157 target.
%A Matyskin AV
%A Angermeier SB
%A Drera SS
%A Prible MC
%A Geuther JA
%A Heibel MD
%J Nucl Med Biol
%V 136
%N 0
%D 2024 Jul 4
%M 39002498
%F 2.947
%R 10.1016/j.nucmedbio.2024.108940
%X <B>BACKGROUND: </B>Actinium-225 is one of the most promising radionuclides for targeted alpha therapy. Its limited availability significantly restricts clinical trials and potential applications of 225Ac-based radiopharmaceuticals.<BR><B>METHODS: </B>In this work, we examine the possibility of 225Ac production from the thermal neutron flux of a nuclear reactor. For this purpose, a target consisting of 1.4 mg of 226Ra(NO3)2 (T1/2 = 1600 years) and 115.5 mg of 90 % enriched, stable 157Gd2O3 was irradiated for 48 h in the Breazeale Nuclear Reactor with an average neutron flux of 1.7·1013 cm-2·s-1. Gadolinium-157 has one of the highest thermal neutron capture cross sections of 0.25 Mb, and its neutron capture results in emission of high-energy, prompt γ-photons. Emitted γ-photons interact with 226Ra to produce 225Ra according to the 226Ra(γ, n)225Ra reaction. Gadolinium debulking and separation of undesirable, co-produced 227Ac from 225Ra was achieved in one step by using 60 g of branched DGA resin. After 225Ac ingrowth from 225Ra (T1/2 = 14.8 d), 225Ac was extracted from the 226Ra and 225Ra fraction using 5 g of bDGA resin and then eluted using 5 mM HNO3.<BR><B>RESULTS: </B>Measured activity of 225Ac showed that 6(1) kBq or 0.16(3) μCi (1σ) of 225Ra was produced at the end of bombardment from 0.9 mg of 226Ra.<BR><B>CONCLUSIONS: </B>The developed 225Ac separation is a waste-free process which can be used to obtain pure 225Ac in a nuclear reactor.