Disclosed are a replaceable fusion core that can be inserted and removed from the core of a nuclear fission reactor, thereby enabling the replacement of materials exposed to neutron flux and reducing outage times and "hybrid reactor, method, and device for improved nuclear fusion reactors to provide sufficient flux of fast neutrons with sufficient energy to transmutate transuranic wastes from nuclear fission and to be used in improved nuclear fuel cycles so as to effectively reduce the amount radio-toxicity, and the risks and costs of the disposal of nuclear waste, thereby reducing the cost of nuclear energy and increasing its acceptability as an energy source. This abstract is intended for use as a scanning tool only and is not intended to be limiting.
 This invention was made with U.S. government support under Grant Nos. DE-FG02-04ER54742 and DE-FG02-04ER54754 awarded by the United States Department of Energy. The U.S. government has certain rights in the invention.