Thorium Fuel Cycle Option Screening in the United States

As part of a nuclear fuel cycle evaluation and screening (E&S) study, widely ranging thorium fuel cycle options were evaluated, and their performance characteristics and challenges to implementation were compared to those of other nuclear fuel cycle options based on criteria specified by the Nuclear Energy Office of the U.S. Department of Energy. The evaluated nuclear fuel cycles included the once-through, limited, and continuous recycle options using critical or externally driven nuclear energy systems. The E&S study found that the continuous recycle of ²³³U/Th in fuel cycles using either thermal or fast reactors is an attractive promising fuel cycle option with high effective fuel resource utilization and low waste generation, but they did not perform quite as well as the continuous recycle of Pu/U using a fast critical system, which was identified as one of the most promising fuel cycle options in the E&S study. This is because compared to their uranium counterparts, the thorium-based systems tended to have higher radioactivity in the short term (~100 years postirradiation), because of differences in the fission product yield curves, and in the long term (100 000 years postirradiation), because of the decay of ²³³U and daughters, and because of higher mass flow rates due to lower discharge burnups. Some of the thorium-based systems also require enriched uranium support, which tends to be detrimental to resource utilization and waste generation metrics. Finally, similar to the need to develop recycle fuel fabrication, fuels separations, and fast reactors for the most promising options using Pu/U recycle, the future thorium-based fuel cycle options with continuous recycle would also require such capabilities; however, their deployment challenges are expected to be greater since past development of such facilities has not reached a comparable level of maturity.