Investigating the potential advantages of using thorium-based fuel as an advanced nuclear fuel in a typical boiling water reactor assembly (BWR)

The long-term sustainability of Boiling water reactor (BWR) fuel cycles is challenged by the accumulation of reactor-grade plutonium (rgPu), minor actinides (MAs), and high-level radiotoxic waste in spent fuel. This study investigates the potential of thorium-based fuels as an alternative to conventional uranium dioxide (UO₂) to address these issues and improve fuel cycle performance. Several thorium fuel combinations-namely (Th, U)O₂, (Th, ²³³U)O₂, and (Th, rgPu)O₂-were analyzed within an BWR fuel assembly and compared to conventional UO₂ fuel. Key parameters such as the infinite multiplication factor (k_inf), fissile inventory ratio (FIR), reactor-grade plutonium (rgPu), minor actinides (MAs), significant fission products (¹³⁵Xe and ¹⁴⁹Sm), and overall radioactivity were evaluated across various effective full power days (EFPDs). To assess the feasibility of the proposed fuel types, key safety parameters including the fuel temperature coefficient (FTC), void reactivity coefficient (VRC), and effective delayed neutron fraction (β_eff) were evaluated. Control rod worth (CRW) was also calculated for each fuel type to analyze its impact. Additionally, radial power distribution was examined. The results indicate that both (Th, ²³³U)O₂ and (Th, rgPu)O₂ extend the fuel cycle, with over 56% of the initially loaded plutonium being consumed during operation. The temperature reactivity coefficients of the proposed fuels remain within acceptable safety margins, and the radial power distribution shows no significant power peaking within the fuel rods, suggesting favorable thermal-hydraulic and structural performance.