For high-fidelity simulations of fluid dynamics in molten salt reactor (MSR), even though a supercomputer is able to suppress the period of each simulation, the consequent expense is still prohibitively costly. A possible way to overcome this limitation is the use of Reduced Order Modelling (ROM) techniques.

This study aims to evaluate the accuracy of the ROM methods for reconstructing the velocity and pressure fields.

Two ROM methods based on the Proper Orthogonal Decomposition (POD) with both Galerkin projection, namely FV-ROM (ROM based on Finite Volume approximation) and SUP-ROM (ROM with supremizer stabilization), were established for fluid dynamics of MSR. Then, both methods were tested on the unsteady cases of liquid-fueled molten salt reactor (LFMSR) for comparison and applicability analysis.

The FV-ROM demonstrates notable advantages in both velocity prediction and computational efficiency. For laminar and turbulent transient simulations, the average velocity L² relative errors are less than 0.5% and 0.6%, respectively, with acceleration ratios of approximately 1 500 and 1 000 times for single time steps. Conversely, the SUP-ROM scheme demonstrates significant prowess in pressure prediction, achieving remarkably low pressure average L² relative errors of 0.20% and 0.38% for laminar and turbulent transient scenario, respectively.

Results of this study indicate that combination of SUP-ROM and FV-ROM for fluid dynamics computations of MSR can significantly enhance computational efficiency and ensure reliability and accuracy of transient simulation.