High-resolution neutron spectrum regulation for promoting transuranic isotope production

The research team from Shanghai Jiao Tong University have made significant progress in transuranic isotope production. The team has proposed a method for neutron spectrum regulation with high spectral resolution across the full energy range and applied it to the in-reactor production of transuranic isotopes. The proposed optimization schemes only disperse certain nuclides into the targets without modifying the reactor design parameters, making them simple and feasible. The new method achieves efficient and precise neutron spectrum optimization, maximizing the production of transuranic isotopes.  The related research has been published in the journal Nuclear Science and Techniques.

Neutron spectrum regulation enhances the in-reactor transuranium isotopes production

Transuranic isotopes are primarily produced through in-reactor irradiation, but this process faces the challenges of low nuclide conversion rates and high production costs. Neutrons of different energy regions have different capacities for inducing various nuclear reactions, and regulating the neutron spectrum can control the nuclear reaction process. Therefore, by adjusting the neutron spectrum within the irradiation channel, fission losses can be reduced, and the production efficiency of transuranic isotopes can be increased.

Sophisticated computational process

The challenge of regulating the neutron spectrum is substantial due to the neutrality of neutrons. This neutron spectrum regulation method comprises four modules: a neutron spectrum perturbation module, a neutron spectrum calculation module, a neutron spectrum valuation module, and an intelligent optimization module. The full energy range (0~20 MeV) is divided into 238 energy bins and the energy transfer relationships for 423 nuclides are built across these bins, enabling rapid and accurate neutron spectrum calculations. Subsequently, the proportions of these 423 nuclides are adjusted by utilizing a genetic algorithm to manipulate the neutron spectrum within a specific spatial region, obtaining the desired neutron spectrum.

Remarkable Optimization Results

The High-Flux Isotope Reactor (HFIR) is currently the primary facility for transuranic isotope production, accounting for 70% of the global ²⁵²Cf supply. The HFIR irradiation scheme of transuranic isotope production, which is currently the optimal irradiation scheme available. If this research can further enhance these state-of-the-art irradiation schemes through neutron spectrum regulation, the significance of this work can be demonstrated. Without modifying the layout of the reactor and irradiation channels, a mere dispersion of a little of nuclides in the target can improve the yield of ²⁵²Cf by 12.16% and that of ²³⁸Pu by 7.53% to 25.84%.

Broad Application Prospects

Due to the significance of neutron spectrum regulation in nuclear science and engineering, the scope of application for this study is quite broad. For instance, in the field of nuclear waste transmutation, precise regulation of neutron spectra is crucial for optimizing transmutation efficiency and reducing secondary waste. In the realm of neutron activation analysis, when analyzing certain elements, utilizing specific neutron energy regions can significantly enhance sensitivity or selectivity, thereby optimizing the analytical results.

Future Directions

The research team plans to expand this research work into the field of medical isotope production to enhance the yields of medical isotopes such as Mo-99, I-131, and Lu-177.

The complete study is accessible via DOI：10.1007/s41365-025-01764-7

Nuclear Science and Techniques (NST) is a peer-reviewed international journal sponsored by the Shanghai Institute of Applied Physics, Chinese Academy of Sciences. The journal publishes high-quality research across a broad range of nuclear science disciplines, including nuclear physics, nuclear energy, accelerator physics, and nuclear electronics. Its Editor-in-Chief is the renowned physicist, Professor Yu-Gang Ma.