The nuclear fuel cycle is the series of industrial processes that support the production of electricity in nuclear power reactors.  While the United States currently practices the ‘open’ fuel cycle in which used uranium fuel is not reprocessed or recycled, ‘closed’ fuel cycles in which used fuel is reprocessed and some of the residual actinides and fission products are recycled into advanced reactors are under consideration.  By fissioning unused actinides and transmuting selected long-lived radioactive fission products, closed fuel cycles may benefit the sustainability of the resource base and simplify the disposal of residual high-level wastes.  For example, it has been shown that if all transuranic actinides in used water reactor used fuel are fissioned, the radiotoxicity of the residual waste drops below that of an equivalent mass of crustal uranium and its decay daughters within a few hundred years.
This talk will summarize the status and objectives of domestic closed nuclear fuel cycle research and development activities.  It will be shown that the efficiency of separation, which is currently planned to be achieved at the elemental level through aqueous or pyrometallurgial processes, strongly affects the benefit of a closed fuel cycle to waste disposal.  Further, partitioning at the isotopic level would be advantageous in several cases as it enables different transmutation and disposal strategies to be pursued for each isotope.     An overview of candidate species will be provided.