[en] An analysis of the important technical and economic parameters related to the timing and future deployment of nuclear power in the US is presented. The anaysis is used first to form the basis of a set of alternative nuclear strategies and then to assist in a critical evaluation of these strategies. The strategies involve major decisions on breeder commercialization, fuel cycle development, and strengthening the nuclear option in the US. DOE energy projections indicate that nuclear power must play a substantial role in meeting future US energy needs, even under assumptions that are otpimistic with respect to energy conservation and the increased use of coal-fired generating plants. Also, estimates indicate that nuclear power can have a substantial cost advantage in certain areas of the US. However, these estimates involve significant uncertainties, such as the relative environmental impact of the nuclear and coal cycles and the costs of meeting new environmental performance standards. There are three main elements in the fission portfolio: programs which extend the uranium resource base or which add to the efficiency of its use; breeder programs; and enabling programs