Fluoride-salt-cooled, high-temperature reactor (FHR) technology combines the robust coated particle fuel of high-temperature, gas-cooled reactors with the single phase, high volumetric heat capacity coolant of molten salt reactors and the low-pressure pool-type reactor configuration of sodium fast reactors. This paper discusses one key technology area required to further define and develop the FHR: the thermal hydraulic performance of the core, primary system and second loop. Shanghai Institute of Applied Physics (SINAP) is leading the China Academy of Science (CAS) FHR program. A TMSR-SF1 reactor with a fluoride cooled pebble bed design has been suggested by SINAP, and the design is currently in progress. For this preliminary thermal hydraulic assessment, a TMSR-SF1 system model was developed using RELAP5. The RELAP5 model was used to help define and size systems such as the intermediate coolant salt selecting. A loss of flow transient was also simulated to evaluate the performance of the reactor during an anticipated transient event. A steady-state calculation was carried out and the calculated initial conditions show the influence of different salt. The loss of forced flow (LOFF) transient simulation results show that the passive residual heat removal system can effectively remove all decay heat from the primary loop under this extreme accident scenario. Some initial recommendations for modifying system component designs, such as heat exchanger with different salt and install place of pump, are also discussed.

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