Conceptual study of a supercritical CO2-cooled, triply periodic minimal surface lattice-based microreactor

Advancements in additive manufacturing (AM) processes have made it increasingly feasible to consider optimized shapes such as triply periodic minimal surface (TPMS) lattices for heat transfer applications, ranging from heat exchanger designs to nuclear fuel elements. This study introduces a TPMS-lattice-shaped nuclear core and compares its performance against that of a traditional pin-based design. A publicly available design that relies on typical fuel pin elements for a fast spectrum, supercritical CO 2 (sCO 2 )-cooled reactor with a direct Brayton cycle was selected as the reference design. The same core materials were used in the TPMS core to ensure a fair comparison between both geometries. Due to the complexity of this type of geometry, innovative modeling strategies were introduced. The thermal performance of the TPMS fuel element was analyzed using a computational scheme that combined high-fidelity computational fluid dynamics (CFD) with Multiphysics Object-Oriented Simulation Environment (MOOSE)-based 1D thermal hydraulics, coupled with 3D heat transfer. Monte Carlo reactor physics analyses using unstructured meshes in Serpent were employed to characterize the core performance and verified against a native constructive solid geometry TPMS lattice implementation in OpenMC. When it comes to fast spectrum reactors, TPMS geometries are neutronically equivalent to pin geometries. However, TPMS-based fuel elements offer improved heat transfer performance, enabling the power density to be increased up to 59% while still meeting the peak material temperature requirements. A downside of TPMS lattices is the additional pressure drop per unit length, which may be manageable when factoring the pumping power costs into the total energy generated by the proposed microreactor concept.