Impact of Accident-Tolerant Fuels on the Neutronics and Safety Performance of the NuScale Small Modular Reactor Using OpenMC Monte Carlo Simulations

The integration of accident-tolerant fuels (ATFs) into the NuScale small modular reactor (SMR) offers significant advancements in safety and efficiency for next-generation nuclear energy systems. This study presents a comprehensive neutronic and safety evaluation of ATF candidates, uranium dioxide (UO2), uranium nitride (UN), UN + U3Si2, UO2 + BeO, and UO2 + SiC, within the NuScale SMR design. The analysis encompasses burnup performance, the evolution of critical actinides, the buildup of strong neutron absorbers such as 135Xe and 149Sm, detailed temperature and power peaking distributions, and the associated neutron irradiation–induced embrittlement of the reactor pressure vessel (RPV) across all five ATF candidates.The isotopic trends revealed distinct differences in fuel efficiency, performance, and the impact on reactivity and fuel cycle optimization. Additionally, due to the limited availability of surveillance data for the NuScale SMR, research and advanced modeling are essential to accurately predict the RPV lifetime.This study represents a comprehensive assessment of the full core of the NuScale SMR using five types of ATFs, analyzed through OpenMC simulations. This study further explored the neutron irradiation–induced embrittlement of the RPV, with the highest neutron fluence of 1.11 × 1018 neutrons/cm2 for UO2 fuel over 57 effective full power years observed at the 0-T surface, followed by 6.5 × 1017 neutrons/cm2 at 1/4-T and 2.1 × 1017 neutrons/cm2 at 3/4-T among other fuels.Advanced ATFs, such as UN + U3Si2 and UO2 + BeO, demonstrated superior performance, exhibiting lower ΔRTNDT values. These findings highlight the potential applications of ATFs in the NuScale SMR design to achieve higher burnup, mitigate poisoning effects, and enhance RPV resilience, thereby offering a safer and more sustainable approach to nuclear power generation.