As an equilibrium core configuration is reached after only a few refueling cycles, equilibrium core energy costs dominate plant economics. Optimization of these costs can therefore lead to nearly optimum energy costs over plant life. A simple reactor state model has been developed that can predict equilibrium core conditions without reference to previous cycles. By coupling this model to an assignment and direct search algorithm, the refueling procedure and core power at equilibrium are determined so that energy costs are minimized. The equilibrium core parameters are then used to establish pre-equilibrium core conditions.