Computational Fluid Dynamics Analysis of a Fluoride Salt–Cooled Pebble-Bed Test Reactor

The fluoride salt–cooled high-temperature reactor (FHR), combining high-temperature graphite-matrix coated-particle fuel (TRISO) for high-temperature gas-cooled reactors and liquid salts developed for molten salt reactors with safety systems that originate from sodium fast reactors, is a new concept reactor. The thermal-hydraulic characteristics of the fluoride salt–cooled high-temperature test reactor (FHTR) are of great importance to the development of the FHR technology, which is mainly ongoing in both China and the United States. In this paper, the thermal hydraulics of the FHTR designed by Shanghai Institute of Applied Physics is studied in different power modes. The one-dimensional temperature distributions of the coolant and the fuel pebble are obtained using a steady-state thermal-hydraulic analysis code for FHR. The detailed local flow and heat transfer are investigated by computational fluid dynamics for the locations that may have the maximum pebble temperature based on the results of a single-channel model. Profiles for temperature, velocity, pressure, and Nusselt number of the coolant on the surface of a pebble as well as the temperature distribution of a fuel pebble are obtained and analyzed. Numerical results indicate that the results of the three-dimensional simulation are in reasonable agreement with those of the single-channel model with a maximum deviation of 17.9%. They also illustrate the safety operation of FHTR in different power modes. This study aims to provide useful information for experimental and mechanism research of FHRs.