A utility system operational planning model of a Liquid Metal Fast Breeder Reactor is developed together with an in-core optimization algorithm to minimize the fuel cost of each cycle. The optimization algorithm determines the batch size and position of two refueling enrichments, the shuffling of partially irradiated fuel, and the fuel to be discharged such that the utility system energy and reactor plant maintenance requirements are met. The in-core model includes a description of the fuel depletion and discrete fuel assembly configuration.