Study of Uranium and Thorium Fuels in Breed-and-Burn Mode

Abstract

The formation of fissile nuclei through breeding conversion is a hot topic in academic research, as it provides a continuous source of nuclear fuel for nuclear reactors. Fast neutron reactors, which have been extensively studied, use natural uranium or low-enriched uranium as the nuclear fuel, achieving burning after uranium-plutonium conversion. Thorium, as another potential fissile fuel, can theoretically be converted into nuclear reactor fuel through the thorium-uranium cycle. In this study, the physical evolution process of nuclear fuel in a specific core parameter is simulated using the Monte Carlo program, and the performance differences of the thorium-uranium cycle and uranium-plutonium cycle in achieving in situ breeding-burning (Breed-and-Burn, B&B) mode are analyzed using neutron balance analysis method. The optimal ratio conditions for achieving self-sustained B&B burning in a thorium-uranium fuel mixed core are investigated. The study shows that for traditional solid-state nuclear reactor cores with a lower fuel proportion, thorium-breeding fuel has poor neutron economy compared to uranium-based breeding fuel, making it more difficult to achieve the B&B mode.