Conceptual Design and Feasibility Analysis of a Modular Supercritical CO2 Fast Reactor Core

Abstract Small Modular Reactor (SMR) is a type of prospective nuclear reactor which has gained extensive attention due to its flexibility, economics, and safety. This paper presents an innovative design of a fast reactor core cooled by supercritical CO2 (SCO2), which can operate at 50 MWth for at least 20 years without refueling. A tube-in-duct structure using beryllium oxide (BeO) as matrix material is proposed. Specifically, the heat generated by the fuel rods is conducted by BeO matrix to adjacent coolant channels, and the SCO2 removes the heat out of the core. Reflectors, shieling, and control rods are applied for operation modification and safety considerations. To enhance the inherent safety, the reactor used double-layer SiC particles with uranium nitride (UN) as fuel. These particles are randomly dispersed in lead contained in the middle of the fuel rods, while the lead offers a better conduction performance. Partial 238U is substituted by minor actinides (MA) to harden the neutron spectra. In the feasibility analysis, both neutronic and thermal-hydraulic calculations are performed under normal condition. Results show that when the reactor is operated at 50 MWth for 30 years, the burnup is about 98.123 MWD/kgHM and the maximum power peaking factor is 1.57 in the radial direction and 1.2 in the axial direction. The inlet/outlet temperature of SCO2 is 660K/873K, while the maximum temperature inside the core holds below 1600 K, which is under the temperature limits. This work may provide a reference for the design of small modular reactor in the future.