Optimization analysis for one-stage method of 99Mo/99mTc

The production of 99 Mo via the one-stage (γ,n) reaction by irradiating an enriched 100 Mo target with an electron beam is a promising technology for medical isotope production, whose efficiency is closely related to target design and processing. This study aims to improve the production efficiency of 99 Mo/ 99m Tc via this one-stage method using a 40 MeV/1 mA electron beam. By employing the Monte Carlo simulation code PHITS, the thickness of the enriched 100 Mo target was optimized to achieve the maximum specific activity of 99 Mo. Simulation results indicate that, through this optimization, the saturation specific activity of 99 Mo reaches approximately 2.3 Ci/g at an optimal target thickness of 14 mm. Based on this optimized configuration and a single irradiation cycle of 26 hours, the proposed setup demonstrates a potential annual production capacity of about 16.1 kCi of 99 Mo, which subsequently yields approximately 25.6 kCi of 99m Tc. The optimized target design for this one-stage 99 Mo/ 99m Tc production method shows favorable performance in both activity output and annual production potential, providing a theoretical foundation for subsequent experiments and system design.