This study aims to analyze the performance of thorium nitride (ThN) fuel with varying uranium-233 enrichments in the core of a Gas-Cooled Fast Reactor (GFR) using OpenMC simulations. Burn-up calculations were performed over a period of 10 years with enrichment levels ranging from 0 to 12. The results show that the k-infinite value tends to increase at enrichments between 0–6, although it rema…