Proliferation-resistant nuclear reactors are disclosed according to some aspects. In one embodiment the proliferation-resistant nuclear reactor comprises a plurality of spherically-shaped micro-fuel elements (MFEs), each comprising a MFE core having one or more fuel kernels, a buffer external to the fuel kernels, and one or more coatings external to the MFE core providing corrosion resistance, erosion resistance, fission product containment, or a combination thereof. The MFEs are not suspended in a solid material and each MFE is sized such that its delay time is less than its accident time. The nuclear reactor further comprises a reactor core containing at least a portion of the plurality of MEs, wherein the reactor core is configured for cross-flow of a coolant.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with Government support under Contract DE-AC0576RLO1830 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.