The effect of a CANDU fuel bundle geometry variation on thermalhydraulic performance

The effect of fuel bundle geometry has been evaluated using the subchannel code ASSERT to enhance the thermalhydraulic performance. Based on the configuration of a standard 37-element fuel bundle, the element diameter in each ring has been changed while those of other rings are kept as the original size. The dryout power of each element in a fuel bundle has been obtained for the modified fuel bundle and compared with that of a standard fuel bundle. The results obtained show that the modification of element diameter largely affects the thermal characteristics of the subchannel on the upper region of a modified element due to the buoyancy drift effect. The explicit effect of the element size on the dryout power of a fuel bundle is investigated by acquiring comprehensive numerical solutions. It is found that the dryout power of a fuel bundle has a tendency to increase as the element size decreases, except for the case where the outer ring is modified. The dependency of the transverse interchange model on the present results has been assessed by examining the dryout power of a bundle for different mixing coefficients and buoyancy drift models.

► We evaluate the effect of fuel bundle geometry on dryout power.
► The element diameter in each ring is modified from a standard fuel bundle.
► The modification of element size affect the thermal characteristics of subchannel.
► The dryout power of a fuel bundle increased as the center ring size decreased.