The National Nuclear Security Administration (NNSA) Office of Defense Nuclear Nonproliferation R&D has commenced a project to evaluate and develop low-enriched uranium (LEU) fuel systems, materials, and fabrication technologies that could be used for compact, advanced LEU (aLEU) fuel, power-producing, high-burnup reactor applications. Potential applications are intended to be off-grid power sources for ship-borne systems and transportable systems to fixed locations, e.g., to a remote base or to a seawater desalination service location. Reactors with these qualities and fuel enrichments between 5 and 20% are atypical. The aLEU Fuel for Nonproliferation Applications Project addresses this technology gap.In the initial stages, the team is assessing key fuel performance criteria, reactor performance criteria, and selection criteria. The project team will identify and leverage the relevant aspects of the mature knowledge base for deployed reactors, both thermal and fast reactor systems, and innovative design features that have been proposed and evaluated to varying degrees but not produced. This project assumes a uranium fuel system at an enrichment of 19.75%. The team will not consider alternate fissile or fertile fuel options. The target power rating is 350 MWt, or approximately 100 MWe with rapid load following capability from 0 to 100% power with an average power rating of approximately 20 MWe. The project assumes a single-batch core lifetime of 30 years. Fuel materials can be monolithic or dispersion, metallic, or ceramic, in rod, plate, or particle bed configurations.Heat transfer from the fuel to the working fluid is necessary for power generation. Fuel geometry (e.g., plate, rod, other) and coolant dictate the heat transfer parameters. Limitations on core size and thermal mass make gas-cooled systems more challenging than liquid cooled. The team considered water and liquid metals first, since molten salt systems would require extensive development and demonstration of corrosion control. The linkage of coolant and reactor types affects not only performance metrics but also drive numerous requirements of the fuel-cladding system. Neutron moderation, its presence or absence, is another significant consideration. Companion reactor analyses depend on, as well as, inform the material studies of the aLEU fuel project.To first order, reactor cooling limits the core power density. Uranium loading and fission controls limit the core life. For a given power rating, coolant, and fuel geometry, a more compact core is possible with higher uranium densities. Recognizing the relevance of uranium density, the project will consider only fuels with a density equal to or greater than UO 2, such as U-xMo alloys and UC, for further evaluation. The project is considering fuels deployed as monoliths (e.g., pellets), dispersion, or as inert matrix. The team will survey fuel systems for applicability with respect to power production, dimensional stability, technology readiness level as well as other criteria. However, demonstration of ...