The back end of the nuclear fuel cycle has been analyzed under current conditions in the United States, including the constraints imposed by the Nuclear Waste Policy Act of 1982 and its amendments. The scenarios for two closed cycles, a regular reprocessing cycle and a reprocessing scheme with cesium and strontium fractionation, are described. The storage of spent fuel discharged from the reactors and the disposal of reprocessed waste are studied for both reprocessing cycles. The economics of waste storage and disposal for the two closed cycles are compared with each other and with the reference once-through cycle. The results show that a standard reprocessing cycle results in the minimum cost for storage and disposal. When reprocessing costs are considered, the closed cycles can compete economically with the once-through cycle only if net reprocessing costs are very low.