Advanced Separation Technologies for Processing Spent Nuclear Fuel and the Potential Benefits to a Geologic Repository

Abstract

The United States Department of Energy's Advanced Fuel Cycle Initiative (AFCI) is developing advanced separation technologies to process spent light water reactor fuel. The purpose of these separation processes is to remove the bulk of the mass of spent nuclear fuel (uranium) and the primary heat generating elements, which limit the amount of material that can be placed in a given amount of repository space. The thermal load to the repository is a function of both short-term heat generating elements, such as the fission products cesium and strontium, and long-term heat generating elements, such as plutonium and americium. For example, calculations of the proposed repository at Yucca Mountain indicate that 99 to 99.9 % removal of these four elements would allow a substantial increase in drift loading in the repository, as much as 50 times greater than for direct disposal of spent fuel. The current AFCI program includes investigation of strategies for the separation of uranium, for low-level waste disposal, and/or for separation and recycle of transuranic elements. Cesium and strontium would be separated for storage (approximately 200-300 years) to allow time for their decay, and would then be disposed as low-level waste. Group separation of actinides, such as neptunium, plutonium, americium and curium, and lanthanides, are also being studied, with interm storage of at least some of the actinides in the repository. These materials would be retrieved at a later date for transmutation in thermal or fast reactors.