A method has been developed to select fuel rod enrichments for a fuel
bundle of a nuclear reactor, the method including: creating an ordered
list of fuel rod types in an initial fuel bundle design; perturbing at
least a subset of the fuel rod types in the initial fuel bundle design to
generate a plurality of perturbed fuel bundle designs; selecting
perturbed fuel bundle designs having fuel rods with allowable fuel
enrichment types and an allowable average enrichment for the perturbed
bundle; determining a difference between each of the selected perturbed
fuel bundle design and the initial fuel bundle design, and creating a
group of the perturbed fuel bundle design having a difference less than a
predetermined threshold difference value.