Neutronic performance of ThCl4–PuCl3 fuel with advanced moderator and blanket configurations in dual fluid reactor

This study performs a comprehensive neutronic evaluation of plutonium-bearing chloride fuels, moderator materials, and blanket configurations for molten-salt Dual Fluid Reactors (DFRs). Burnup analyses showed that the fissile inventory and plutonium isotope vector strongly govern reactivity behavior, with base fuel (derived from 4.95 wt%-enriched UO2 spent fuel irradiated in a VVER-1200 reactor and cooled for 10 years) and 10BP40 (239Pu content in the base fuel is reduced by 10 wt% and replaced with an equivalent amount of 240Pu) fuels providing the longest cycles in the reference geometry, while 80BP38 achieved higher keff than 60BP40 due to its elevated 240Pu fraction. Moderator optimization identified a 0.05 cm YH1.85 layer as the most effective spectral shifter, substantially increasing keff and cycle length but introducing excess reactivity for fuels with low 240Pu. In contrast, MgO–BeO exhibited weak moderation and minimal impact on system performance. Replacing the UCl3 blanket with a ThCl4–PuCl3 blanket significantly extended cycle length and improved neutron economy across all configurations, with SiC tubes offering the best combination of high burnup, acceptable reactivity margins, and fast-spectrum preservation. Temperature feedback analyses confirmed that several configurations exhibited negative Doppler coefficients necessary for inherent safety. Overall, ThCl4–PuCl3 salt is found to be neutronically suitable as both a fuel and breeder blanket material for the Dual Fluid Reactor geometry. © 2026 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.