Pre-conceptual core design of a small modular fast reactor cooled by supercritical CO2

A Small Modular fast reactor cooled by Supercritical CO2 (SMoSC) is pre-conceptually designed through three-dimensional coupled neutronics/thermal-hydraulics analysis. The power rating of the SMoSC is designed to be 300MWth to meet the energy demand of small electrical grids. The excellent thermal properties of supercritical CO2 (S-CO2) are employed to obtain a high thermal efficiency of about 40% with an electric output of 120MWe. MOX fuel is utilized in the core design to improve fuel efficiency. The tube-in-duct (TID) assembly is applied to get lower coolant volume fraction and reduce the positive coolant void reactivity. According to the coupled neutronics/thermal-hydraulics calculations, the coolant void reactivity is kept negative throughout the whole core life. With a specific power density of 9.6kW/kg and an average discharge burnup of 70.1GWd/tHM, the SmoSC can be operated for 20 Effective Full Power Years (EFPYs) without refueling.