Implementation and Validation of the Second-order TVD Scheme in the Thermal-hydraulic Analysis Module of FRTAC

For the developmental and risk-evaluation phases of next-generation nuclear power platforms — specifically those utilizing liquid metal as a coolant — the availability of high-resolution thermo-hydraulic computational frameworks is indispensable. This paper details the implementation and validation of a second-order Total Variation Diminishing (TVD) scheme within the thermal-hydraulic analysis module of the Fast Reactor Transient Analysis Code (FRTAC), a system analysis software developed by the China Institute of Atomic Energy. The primary objective was to enhance the code’s predictive accuracy by mitigating the numerical diffusion inherent in the original first-order upwind scheme. The research involved a comprehensive reconstruction of the underlying solver, incorporating a robust flux limiter to suppress numerical oscillations at sharp gradients while preserving high-order accuracy in smooth flow regions. The newly developed module was systematically validated against two internationally recognized benchmark cases. For transient analysis, the module’s simulation of the Edwards blowdown experiment demonstrated good agreement with experimental data for the rapid depressurization process. For steady-state heat transfer analysis, simulations of the U.S. Energy Technology Engineering Center steam generator test cases A5 and A7 yielded outlet temperature predictions with a maximum relative deviation of less than 1.65% from experimental values. The validation results confirm that the enhanced module possesses the requisite accuracy and versatility for handling both severe transient and steady-state thermal-hydraulic phenomena, establishing it as a more reliable tool for reactor safety analysis.