The benefits of sodium-cooled fast reactors (SFR) are well known and include: the possibility of a closed fuel cycle, proliferation resistance, waste minimization and breeding capabilities. Metallic fuel used in SFR has well demonstrated irradiation performance. More studies are, however, necessary to optimize and extend operational and safety limits through reduction of uncertainties in transient fuel behaviors and fuel failure thresholds. This paper describes the experimental Research and Development (R&D) program aimed at providing the necessary data to support the development of SFR optimized safety limits. This program integrates Separate Effects Testing (SET) and Integral Effects Testing (IET), combined with advanced Modelling and Simulation (M&S) to provide "solution-driven, goal-oriented, science-based approach to nuclear energy development" described in the Department of Energy Office of Nuclear Energy (DOE-NE) Roadmap. This R&D program, finally, focuses on delivering the science-based information necessary for supporting the licensing and utilization of SFR based on metallic fuel. Three research areas centered on fuel development by SET testing are described in this paper: 1) Microstructural, Chemistry and Material properties; 2) Thermo-mechanical behavior; and 3) Source term and fission product behavior. Preliminary results from these SET studies and the current instruments and experimental plan are presented.