image: Direct electron-beam irradiation of a molten salt target generates bremsstrahlung photons that induce uranium photofission for 99Mo production, and comparable photofission cross-sections of 238U and 235U reduce reliance on 235U, enabling direct use of natural or depleted uranium.
Credit: Xiao-Xiao Li
Exploring Novel Production Pathways for the Medical Isotope 99Mo
99Mo is one of the most extensively utilized diagnostic radionuclides in nuclear medicine. Conventional 99Mo production relies predominantly on research reactors, which face challenges such as the vulnerabilities of a concentrated supply chain, aging infrastructure, nuclear proliferation risks, and substantial generation of radioactive waste. To explore more sustainable and safer production technologies, the research team has proposed a novel technical approach. This method employs high-energy electrons generated by an electron accelerator to directly irradiate a flowing molten salt target containing natural uranium for 99Mo production.
Photofission-Dominated Production Mechanism
In this approach, 99Mo is primarily generated through the photofission reaction of 238U. This process eliminates the reliance on 235U, allowing for the direct use of natural or even depleted uranium. This significantly mitigates nuclear proliferation risks and offers substantial advantages in terms of material security. As noted by Thomas Ruth in Nature: "The production rate of 99Mo is several orders of magnitude lower, but this is outweighed by the advantage of using safer materials".
Systematic Optimization Analysis of Key Parameters
The research team identified fluoride-based molten salt systems as the optimal target material due to their higher bremsstrahlung energy loss rate and superior photon yield, which contribute to a higher 99Mo production rate. An electron beam energy range of 40–80 MeV is recommended. Furthermore, temperature field analysis of the flowing molten salt confirmed that the system can effectively prevent localized overheating and salt boiling, validating its engineering feasibility.
Capacity Assessment Demonstrating Potential for Scalable Application
The maximum annual production capacity of 99Mo via this technical route is estimated to reach approximately 4486.49 Ci, sufficient for several hundred thousand to a million medical diagnostic procedures. This output corresponds to approximately 16.37% of China's projected demand for 2030, demonstrating the potential for economically viable, large-scale production capability of this approach.
Advancing the Security of Nuclear Medicine Isotope Supply
This research integrates advanced accelerator technology with molten salt chemistry, proposing a non-reactor-based, low-risk, and high-capacity production route for 99Mo. It provides a new technical pathway for establishing distributed, modular 99Mo production bases within China, contributing to reduced external dependency and safeguarding public health.
The complete study is via by DOI: https://doi.org/10.1007/s41365-026-01908-3
Journal
Nuclear Science and Techniques
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
Production of 99Mo via photofission reaction in natural-uranium-bearing molten salt targets
Article Publication Date
9-Feb-2026