Neutronic design of a novel small modular reactor based on the dual-cooled accident tolerant fuels using systematic methodology: Fuel assembly and core pattern evaluation via artificial neural network

Abstract

This study investigates the design of a novel Small Modular Reactor (SMR) concept utilizing Dual-Cooled Accident Tolerant Fuel (DC-ATF). The DC-ATF incorporates U₃Si₂ fuel pellets clad in FeCrAl, enhancing safety and accident tolerance. A systematic approach was employed, beginning with the evaluation of 4000 unique fuel assembly configurations varying the number and arrangement of Integrated Burnable Absorbers (IBAs). Fifty configurations in each category were rigorously simulated using the MCNP code, and the results were used to train Artificial Neural Networks (ANNs) to predict the performance of the remaining assemblies. This approach facilitated the identification of suitable fuel assembly designs for each IBA category. Subsequently, these assemblies were integrated into 55 distinct reactor core configurations, varying the distribution of IBA-containing assemblies within a 37-assembly core arranged in a square lattice. Neutronic simulations were performed to evaluate core criticality, power distribution, burnup characteristics, and temperature coefficients. The results demonstrate that the proposed DC-ATF SMR exhibits favorable safety margins, including negative temperature coefficients (−2 pcm/K for fuel and −33.89 pcm/K for coolant) and acceptable power peaking factors (1.58 at beginning of the cycle). Burnup calculations indicate a first core cycle length exceeding 1800 effective full power days (EFPD), a significant increase compared to conventional UO₂-fueled SMRs of similar size and output power, which typically achieve around 730–1330 EFPD. This improvement is primarily attributed to the higher uranium density of U₃Si₂ fuel, enabling increased fissile material loading.