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

• Neutronic performance of ThCl 4 –PuCl 3 fuel is analyzed for Dual Fluid Reactors. • A 0.05 cm YH 1.85 moderator layer increases k eff and extends the fuel cycle. • ThCl 4 –PuCl 3 blanket significantly extends the reactor fuel cycle. • SiC tube with ThCl 4 –PuCl 3 blanket provides the best burnup–safety balance. 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 UO 2 spent fuel irradiated in a VVER-1200 reactor and cooled for 10 years) and 10BP40 ( 239 Pu content in the base fuel is reduced by 10 wt% and replaced with an equivalent amount of 240 Pu) fuels providing the longest cycles in the reference geometry, while 80BP38 achieved higher k eff than 60BP40 due to its elevated 240 Pu fraction. Moderator optimization identified a 0.05 cm YH 1.85 layer as the most effective spectral shifter, substantially increasing k eff and cycle length but introducing excess reactivity for fuels with low 240 Pu. In contrast, MgO–BeO exhibited weak moderation and minimal impact on system performance. Replacing the UCl 3 blanket with a ThCl 4 –PuCl 3 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, ThCl 4 –PuCl 3 salt is found to be neutronically suitable as both a fuel and breeder blanket material for the Dual Fluid Reactor geometry.