This video, produced by the Science Channel with the assistance of Argonne National Lab, discusses some of the work being done to perfect closed-cycle “fast” nuclear reactors. Nearly all reactors used for energy production are based on a light-water reactor model that are inefficient (fuel rods must be replaced after only 5% of the uranium-235 has been used) and create wastes with very long half lives.
Instead of using water, fast reactors employ a coolant – typically liquid sodium – that doesn’t slow down neutrons. The resulting “fast” neutrons have less tendency to be captured by uranium atoms and be converted to plutonium or higher actinides.
ANL’s fast reactors treat spent reactor fuel not as waste but as a rich source of recycled energy. Because they permit the reprocessing of spent nuclear fuel, fast reactors can operate through what is known as the “closed fuel cycle,” which dramatically increases the efficiency of uranium use and minimizes the discharge of plutonium and minor actinides as waste. A closed fuel cycle could – at least theoretically – use 90 percent of the energy available in uranium.