2017 | AFC ACCOMPLISHMENTS 180 The plan outlines the different activities required to support the development of advanced metallic fast reactor fuel systems.To achieve this goal, the recommended approach is to continue programs in irradiation testing, post-irradiation examinations, and fuel element fabrication, but also increase the emphasis placed on mechanistic fuel system modeling, literature reviews, validation of models against historic fuel performance data, and evaluation of the impact of prospective fuel designs on reactor plant performance (Figure 1). In this manner, once an irradiation test program is designed and initiated, there is not only an improved likelihood that the fuel system will behave as expected but there is also a better chance, if the testing is successful, that the fuel design will result in substantial improvements to reactor plant economics and/or safety. Project Description: Potential customers to the Advanced Fuels Campaign (AFC) include the Versatile Test Reactor (VTR) and the burner reactor concepts being pursued by the Depart- ment of Energy, breed-and-burn reactor designs (TerraPower), and fuel systems for more conven- tional sodium-cooled fast reactors (GE-Hitachi, Advanced Reactor Concepts, OKLO). Given the broad array of potential applications, the approach will be to explore technically relevant fuel designs but also to develop an improved understanding of fuel performance fundamentals so that specific fuel designs for a given reactor plant can be developed with reduced time and cost.To make matters more specific, two broad classes of fuel designs will be pursued: (1) once- through fuel systems; and (2) fuels for enhanced actinide utilization that would require recycling. For a once-through design, a major focus will be on the elimination of bond sodium, which should facilitate the direct disposal of the fuel in a geological repository.This work will build upon existing efforts to fabri- cate and characterize the behavior of sodium-free annular fuel, but it will also emphasize fuel alloys that are likely to be employed for the VTR. Fuel designs for enhanced actinide utilization, however, have significantly different constraints and objectives than a once-through fuel system.The focus here will be on fuel shapes that can be fabricated within a hot cell and fuel element designs that can achieve high energy and power density. Update to the Advanced Reactor Fuels Irradiation Test Plan Principal Investigator: Gary Povirk Collaborators: Doug Dempsey, Jason Harp, Steven Hayes