Daydas, SemraTiftikci, Ali2026-04-252026-04-2520261738-5733https://doi.org/10.1016/j.net.2025.104079https://hdl.handle.net/11486/8302This study investigates the feasibility of using a Uranium-Manganese (U-Mn) alloy as an alternative fuel for the Dual Fluid Reactor (DFRm) concept to increase the temperature margin, along with a Magnesium Oxide-Beryllium Oxide (MgO-BeO) ceramic fuel tube. Neutronic analyses were performed using the SERPENT 1.1.7 Monte Carlo code with the ENDF/B-VII cross-section library to evaluate fuel performance, reactivity behavior, and safety margins. The results indicate that the U-Mn fuel exhibits lower keff values and shorter fuel cycle length to those of the U-Cr fuel, while providing the advantage of a lower eutectic temperature. Reactivity coefficients found to be negative for both fuel and coolant with the SiC fuel tube, ensuring inherent safety during temperature excursions. However, for the MgO-BeO configuration, the reactivity coefficients for MgO-BeO were found to be positive, which represents a critical drawback of this material; hence, further geometrical optimization is required. Consequently, although U-Mn fuel maintains negative temperature feedback under SiC-based configurations, alternative tube materials such as MgO-BeO require further optimization to ensure stable and inherently safe reactivity behavior throughout the fuel cycle. Future research could focus on optimizing reactor geometry to enhance the utilization potential of U-Mn fuel.eninfo:eu-repo/semantics/openAccessDual fluid reactorMolten-salt reactorLead-cooled reactorHigh temperature reactorUranium-manganeseMagnesium Oxide-Beryllium oxideArticle58410.1016/j.net.2025.1040792-s2.0-105029717103Q1WOS:001644183500001Q10000-0003-3323-4092