Experimental Study on Production of Medical Nuclide ²²⁵Ac with 100 MeV Cyclotron

The radionuclide production experiment was conducted at the 100 MeV cyclotron at China Institute of Atomic Energy. Fluka code was used to simulate the isotope activities of ^224-228Ac produced by proton beam irradiation on ThO₂ powder target with different thicknesses. The variation of yield with thickness of 1, 5 and 10 mm ThO₂ targets was studied, and the target with 5 mm thickness was selected according to the law of yield variation and cooling condition. A target system for the irradiation of ThO₂ powder target was designed, and the production of ²²⁵Ac nuclide with low current intensity was carried out. The functions of indirect measurement of proton beam intensity, real time monitoring of target temperature and compressed air cooling of target were realized, ensuring the safety of irradiated targets. After irradiation, ThO₂ target was chemically treated and ²²⁵Ac was extracted. After ²²⁵Ac and ²²¹Fr reached the decay equilibrium, the γ of ²²¹Fr decay with 218 keV was measured by γ spectrometer. The activity of ²²⁵Ac at the end of bombardment is 2.29×10⁷ Bq and the yield is 2.39×10⁵ Bq/(μA·h).