This research study of the optimation of thermal power and core size in a GFR type reactor with natural metallic uranium fuel (U-10%wt Zr), supercritical carbon dioxide (S-CO2) as a coolant, and cladding made of stainless steel 316 with a thermal power of 500 MWt. This research uses a modified CANDLE burnup strategy where the reactor core is divided into 10 regions radial with the same volume. …