Comparative neutronic and burnup assessment of alternative uranium-based fuels in a Very-High-Temperature Reactor

This study presents a comprehensive neutronic assessment of advanced accident-tolerant fuel (ATF) candidates for application in a 600 MWth prismatic Very High Temperature Reactor (VHTR). Four uranium-based compounds—U 2 Ti, UB 2 , UC, and UN—were systematically evaluated and compared with conventional UO 2 fuel using high-fidelity Monte Carlo simulations. The analysis focused on key performance metrics, including reactivity evolution, neutron economy, isotopic transmutation behavior, radioactivity buildup, and inherent safety feedback over the entire irradiation cycle. Relative to UO 2 , the candidate fuel configurations increased the calculated criticality duration by 21.5–33.8%, with UC and UN exhibiting the greatest reactivity persistence. The calculated power peaking factors (PPFs) showed only a small variation among the investigated fuels, ranging from 1.21 for UO 2 to 1.27 for the proposed fuel configurations, indicating that the proposed fuels do not substantially alter the power distribution compared with the reference UO 2 case. All investigated fuels preserve negative reactivity coefficients and favorable delayed-neutron fractions, supporting robust inherent safety feedback.