Fast reactor designs in the USA: changing goals and options

Liquid metal fast reactor developments in the USA have narrowed to two basic goals: (1) nominally inherently safe modular designs with passive cooling capability and minimum requirements for safety-grade equipment; and (2) an integrated fuel cycle based on pyroprocessing and metal alloy fuel material. The current goals reflect basic departures from the originally conceived incentives and design goals for reactors capable of high neutron efficiencies. The economic, logistic, and institutional changes in the applicable factors that drive the changing goals are reviewed. The paper describes the current technical status and possible strategies for reaching a prototype stage during the next few decades. The key technical developments that appear to make the current goals attractive and feasible are surveyed. Prototypes have operated for several dozen reactor years and have experienced numerous non-nuclear incidents. None of these events appear to pose significant obstacles to the attainment of the safe and reliable operation of fast reactors. The historical developments leading to the current status are summarized in four periods from 1948 to 1993. The main factors discussed include the dramatic changes in the size and dynamics of plutonium and uranium supplies, the improved picture on fossil fuel supplies, and the resulting decline in the near-term cost competitiveness of nuclear options in the USA. The dominant role of public perceptions and the sources of misperceptions are discussed. The effects of federal regulations and litigation have also been very important. The combination of these changing circumstances serve to defer for several decades the potential for realizing the economic value of excess breeding gain. Nevertheless, a path of economically driven near-term and long-term development and deployment is foreseen. The promising near-term path involves the use of modular fast spectrum burner reactors that offer good prospects of achieving good economics near-term. These can also provide vital national security benefits by using their capability for sequestering plutonium from decommissioned nuclear weapons safely.