The total reactor feed rate under equilibrium refueling is minimized by adjusting the exit irradiation of the fuel in specified burnup zones while obeying constraints on excess reactivity and on the power shape in the reactor. The gradients used in the numerical search are obtained via the explicit generalized perturbation theory. A computer code, called OPTEX, was written to solve this optimization problem, using a successive linearization method that requires a small number of flux calculations to converge. Tests on a CANDU-type lattice have shown that this approach can be used to simultaneously obtain an optimal control poison distribution.