Sets of basic poison depletion curves have been computed and used with a linear and a nonlinear program to match as closely as possible a required optimized fuel assembly depletion profile. The technique is applied to the fuel assembly design of the Three Mile Island-Unit One reactor wherein either solid poison or annular poison rods are used to contain burnable poisons (BPs). These BPs are either in the form of fine particles or spheroids uniformally distributed in the BP rods. The optimization technique selects the best basic depletion curves to provide an optimum fit to the designed fuel assembly depletion profile. The basic poison depletion curves are nonorthogonal and not complete. Thus, the best fit is not exact because the desired depletion profile requires sudden changes that cannot be attained by the depletion of the BPs.