Investigation of the modified RELAP5 MOD 3.2 capability to simulate the transients of the fluoride-salt high-temperature reactors

Fluoride-salt-cooled high-temperature reactors (FHRs) are a new concept that uses solid fuel and employs high temperature liquid salts as both primary and secondary side working fluids. The thermo-physical properties of the fluoride salts and specific heat transfer correlations have been implemented into the RELAP5-MOD3.2 code to enable the code to simulate the transient thermal-hydraulic response in accidents. The thermophysical properties calculated by the modified code have been benchmarked versus the experimental data. The results of thermal-hydraulic responses of the PB-AHTR in the steady state and simple loss of forced flow from the publications using the RELAP5-3D are used to verify the ability of the modified RELAP5-MOD3.2 to simulate the transients of the FHRs. The code can predict the variations of the thermalhydraulic parameters well whereas some results may distinguish from that calculated by the RELAP5-3D. The unprotected loss of flow is analyzed by the modified code, indicating that the passive residual heat removal system can mitigate the consequence of the accidents.