The high temperature gas-cooled reactor (HTGR) is an advanced reactor type with safety characteristics of Generation IV nuclear energy systems. In the design process of an HTGR, thermal-hydraulic analysis is of great significance. This paper reviews existing methods for thermal-hydraulic calculation of pebble bed HTGRs and proposes a method for the two-dimensional (2-D) simulation using the commercial computational fluid dynamics (CFD) software ANSYS FLUENT. The pebble bed reactor core, fluid flow zones and control rod channels in the reflector are modeled with a porous media approach, while user-defined scalar (UDS) is employed for solving the governing equations of solid temperature in these regions. To incorporate radiation heat transfer among outer surfaces of the porous media region as well as their viewable walls into the calculation, some heat sources in thin layers adjacent to the walls are innovatively added. The method is applied to the steady-state simulation of the 10 MW high temperature gas-cooled reactor-test module (HTR-10). The fuel temperature is far below the safety limit, and the temperature values of the reactor internals agree well with the experimental results, showing that the CFD method adopted in this study predicts the temperature distribution well. Since the effect of radiation heat transfer on the temperature distribution is fully considered, the method can be directly applied to the simulations and studies of some accident conditions.

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