Proliferation Relevance and Safeguards Implications of Partitioning and Transmutation Nuclear Fuel Cycles

Over the last 2 decades there has been renewed interest in developing advanced nuclear reactors and fuel cycles. Many of these advanced design concepts require or can use fuel elements that contain actinides recycled from light water reactor spent fuel. Irradiation of these elements in fast nuclear reactors is supposed to transmute them into less toxic isotopes and reduce their mass. Since transmutation is not efficient, recycling into new advanced reactor fuel must occur repeatedly to achieve a substantial reduction in mass. The introduction of this technology will create long-term proliferation risks and require safeguarding not only of plutonium, but also of the other target actinides: neptunium, americium, and curium. These elements will be present in isotopic mixtures for which information on their critical masses is unavailable. This paper provides data on critical masses and spontaneous fission neutron background for the isotopic compositions of the actinides of interest and their evolution in light water reactor fuel of various bumups and during spent fuel storage. These data are complemented by generic estimates of total inventories of these elements present in full-scale partitioning and transmutation fuel cycles being considered for commercial scale and of the time periods required for significantly reducing their proliferation potential.