Advanced Thorium Fuel Configuration for Enhanced Breeding and Reduced Radio-toxicity in Pressurized Water Reactors

Physics

This study investigates the implementation of thorium-based fuel cycles in European Pressurized Reactors (EPR) as a strategic approach to reduce long-term radioactive waste and enhance fuel sustainability. Using Monte Carlo MCNPX 2.6.0 simulations, we analyzed the neutronic performance of hybrid fuel configurations combining uranium dioxide (UO₂) and thorium dioxide (ThO₂) in alternating layers within EPR fuel assemblies. Our results demonstrate that thorium-uranium fuel cycles can reduce long-term radio-toxicity by approximately three orders of magnitude compared to conventional uranium-plutonium cycles, primarily due to minimized production of minor actinides. The research reveals critical insights into uranium-233 breeding dynamics, showing that saturation concentration (~1.29 wt%) is independent of power density, while breeding kinetics strongly depend on neutron flux distribution. Peripheral thorium placement proved inefficient due to low neutron flux, whereas optimized multi-layer configurations enabled sustainable operation with keff stabilization at ~0.8 after 1000 days at 5 GWth power. The study identifies that inner core layers (30-130 cm radial positions) achieve U-233 saturation within 2500 days, contributing significantly to power generation and reaching parity with UO₂ fuel after approximately 1000 days of operation. These findings provide crucial guidance for implementing once-through thorium fuel cycles in existing light water reactors with minimal modifications, offering a practical pathway toward reduced environmental impact and enhanced fuel cycle sustainability in nuclear energy systems.

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