2017 | AFC ACCOMPLISHMENTS 77 ties of both fresh fuel and irradia- tion behavior. A ‘separate effects’ study was conceived to synthesize U3Si2 fuel pellets with controlled levels of oxygen in order to assess the impact on fresh fuel properties. Project Description: A number of factors (e.g. feedstock synthesis, storage, possible air expo- sure, sintering environment) have been found possible of increasing the oxygen content in U3Si2 feed- stock. Presently U3Si2 and other U-Si compounds are synthesized from metallic uranium; while arc melting is suitable for the laboratory setting and is presently employed to fabricate enriched material at the 100g to even kg scale, it is not economi- cally viable at quantities necessary for commercial fuel production.A number of approaches are currently under investigation as means of direct synthesis of U3Si2 from a U-F precursor as well as means of relaxing the handling constraints currently employed to fabricate U3Si2.Any of these proposed routes would result in oxygen levels in U3Si2 at likely higher levels than are found in U3Si2 as produced in the laboratory. Further, process controls will eventually be needed to help constrain proposed industrial processes with regard to oxygen content. The ‘separate effects’ approach to fuel development is well suited to address this problem, as U3Si2 samples can be produced with controlled oxygen levels and limited variations to other microstructural or chemical variables.This facilitates assessment of oxygen’s impact, first on the properties of fresh fuel but additionally to irradiation testing. Success in this work demonstrates the value of a science-based approach to fuel qualification as employed by Advanced Fuels Campaign (AFC) for executing work to support commercialization of ATF concepts. Accomplishments: A series of U3Si2 feedstocks were synthesized to contain a range of oxygen contents at Los Alamos National Laboratory (LANL). Nomi- nally pure U3Si2 high density pellets contain approximately 500 wppm oxygen.The thermodynamics of the U-Si-O system dictate that oxygen