Preliminary performance evaluation of an LEU+ based dual-cooled duplex UO2-ThO2 fuel for advanced PWR assembly

Abstract

This study presents a comprehensive neutronic analysis of dual-cooled annular duplex fuel assemblies incorporating UO 2 -ThO 2 composition for application in advanced pressurized water reactors (PWRs). The investigation employs a 13 × 13 fuel assembly configuration to evaluate the operational enhancement potential of modern reactor systems. The research methodology focuses on the comparative assessment of burnup characteristics across varying uranium enrichment levels, benchmarking the neutronic performance of dual-cooled duplex fuel against conventional solid 17 × 17 and dual-cooled 13 × 13 UO 2 assemblies. The results demonstrate that the proposed UO 2 -ThO 2 dual-cooled duplex fuel configuration with 7 wt.% U-235 achieves discharge burnup equivalent to that of conventional solid UO 2 assemblies. Safety analysis encompasses the quantification of plutonium isotope production and minor actinide generation, revealing that dual-cooled duplex assemblies produce significantly reduced quantities of plutonium isotopes and lower concentrations of minor actinides, including neptunium (Np), americium (Am), and curium (Cm), relative to conventional all-UO₂ assemblies. Reactivity coefficient analysis confirms that both the fuel temperature coefficient (FTC) and moderator temperature coefficient (MTC) maintain consistently negative values throughout the operational cycle. These coefficients not only satisfy but exceed the established safety criteria for PWR operations, thereby demonstrating the enhanced safety margins and operational performance characteristics inherent to the dual-cooled duplex fuel assembly design.