Modeling of fuel salt compressibility in MSR using blastFOAM, reference and accelerated calculations using transfer function

This article presents the work performed to compute the impact of compressibility on the fuel salt of Molten Salt Reactors (MSRs) on reactivity density feedback evolution in the OpenFOAM solver, blastFoam. Reactivity density feedback is a crucial aspect of the chain reaction stability in MSRs. The delay induced by the compressibility of the salt is particularly significant to simulate, especially during transient power variations of very short duration. This study aims to describe the delay induced by the compressibility of the fuel salt in the evolution of density neutronic feedback. To perform this computation, the Correlated Sampling (CS) method was used to compute the neutronic feedback and chained to the compressible results. Based on the results of the study, a methodology is described for obtaining a transfer function to compute density neutronic feedback with only one compressible calculation. This transfer function is computed for verification and illustration purpose on a simplified reactor model and the Molten Salt Fast Reactor (MSFR). It would enable future work to incorporate this physics into non-compressible codes (such as CFD codes and system codes) with minimal computation time.