Study on the Internal Flow Distribution Characteristics of Plate-Type Fuel Elements in THFR

The distribution of area averaged coolant velocities across various coolant channels within the innermost fuel element of the Tsinghua High Flux Reactor (THFR) was analyzed using the FLUENT 2022 R2 under different inlet velocity conditions. Under more conservative assumptions, for uniform velocity inlets, the maximum relative deviation of area-averaged velocities across different coolant channels from the overall area-averaged velocity was less than 0.6%; for artificially constructed non-uniform velocity inlets, the maximum relative deviation of area-averaged velocities across different coolant channels from the overall area-averaged velocity was less than 6%, providing a basis for subsequent reactor design. Non-uniform velocity inlets resulted in significant non-uniformity in the static pressure at the coolant channel inlets. In contrast, the static pressure distribution at the coolant channel outlets was more uniform, with isobaric planes present. The inconsistency in pressure drop led to non-uniform coolant velocity distributions. Therefore, in subsequent reactor structural design, it is crucial to ensure that the coolant at the core inlet is sufficiently mixed.