Abstract：
BACKGROUND: 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.
METHODS: 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.
RESULTS: 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.
CONCLUSIONS: The developed 225Ac separation is a waste-free process which can be used to obtain pure 225Ac in a nuclear reactor.
METHODS: 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.
RESULTS: 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.
CONCLUSIONS: The developed 225Ac separation is a waste-free process which can be used to obtain pure 225Ac in a nuclear reactor.
摘要：
背景：Actinium-225是靶向α治疗最有前途的放射性核素之一。其有限的可用性极大地限制了基于225Ac的放射性药物的临床试验和潜在应用。
方法：在这项工作中，我们研究了核反应堆的热中子通量产生225Ac的可能性。为此,目标由1.4mg的226Ra（NO3）2（T1/2=1600年）和115.5mg的90％富集组成，稳定的157Gd2O3在Breazale核反应堆中辐照48小时，平均中子通量为1.7·1013cm-2·s-1。钆-157具有最高的热中子俘获截面之一，为0.25Mb，它的中子俘获导致高能发射，提示γ光子。发射的γ光子与226Ra相互作用，产生225Ra，根据226Ra(γ，n)225Ra反应。钆去除和分离不受欢迎的，通过使用60g支化DGA树脂在一个步骤中实现由225Ra共同生产的227Ac。从225Ra(T1/2=14.8d)向内生长225Ac后，使用5gbDGA树脂从226Ra和225Ra级分提取225Ac,然后使用5mMHNO3洗脱。
结果:测得的225Ac的活性表明在轰击结束时由0.9mg的226Ra产生6(1)kBq或0.16(3)μCi(1σ)的225Ra。
结论：开发的225Ac分离是一种无废物的过程，可用于在核反应堆中获得纯的225Ac。
方法：在这项工作中，我们研究了核反应堆的热中子通量产生225Ac的可能性。为此,目标由1.4mg的226Ra（NO3）2（T1/2=1600年）和115.5mg的90％富集组成，稳定的157Gd2O3在Breazale核反应堆中辐照48小时，平均中子通量为1.7·1013cm-2·s-1。钆-157具有最高的热中子俘获截面之一，为0.25Mb，它的中子俘获导致高能发射，提示γ光子。发射的γ光子与226Ra相互作用，产生225Ra，根据226Ra(γ，n)225Ra反应。钆去除和分离不受欢迎的，通过使用60g支化DGA树脂在一个步骤中实现由225Ra共同生产的227Ac。从225Ra(T1/2=14.8d)向内生长225Ac后，使用5gbDGA树脂从226Ra和225Ra级分提取225Ac,然后使用5mMHNO3洗脱。
结果:测得的225Ac的活性表明在轰击结束时由0.9mg的226Ra产生6(1)kBq或0.16(3)μCi(1σ)的225Ra。
结论：开发的225Ac分离是一种无废物的过程，可用于在核反应堆中获得纯的225Ac。
