High-Fidelity Multiphysics Modeling of the Molten Salt Fast Reactor with Applications for Reduced-Order Models

The molten salt fast reactor (MSFR) is one of the six Generation-IV reactor designs. In the MSFR, the liquid fuel is also the coolant, which moves throughout the primary circuit. This complex phenomenology requires multiphysics modeling. In this paper, a high-fidelity model of the MSFR is developed in the multiphysics code Cardinal, accounting for neutronics–thermal-hydraulic feedback and the transport of delayed neutron precursors (DNPs) and decay heat precursors (DHPs).NekRS solves the mass, momentum, energy, and DNP and DHP transport equations. NekRS uses a Reynolds-averaged Navier-Stokes k−τ turbulence model. DNPs and DHPs are modeled using a convective diffusion equation with modified source terms that account for radioactive decay. OpenMC is used to solve the neutronics equation. Current limitations in OpenMC do not allow for the modification of delayed neutron source locations. Ongoing efforts look to include this feature in future work to introduce DNP feedback in OpenMC.The Cardinal results showed reasonable behavior for temperature, heat source, velocity, DNPs, and DHPs. In addition, the fission matrix (FM) method is used as a reduced-order neutronics model. The NekRS-FM model is analyzed and compared with the NekRS-OpenMC model. The results showed good agreement between the codes.