2017 | AFC ACCOMPLISHMENTS 137 Figure 1. Archival X521 fuel slug that was used to supply the injection cast U-10Pu-10Zr fuel slug for AFC-3F. Project Description: 2016 work showed the feasibility of arc casting a zirconium wrapped sample suitable for AFC-OA style irradiation tests. 2017 work focused on optimizing the process to determine the optimal zirconium foil thickness, minimize the amount of fuel between the overlapped zirconium layers, and to characterize the foil/fuel alloy bond. Several casting trials were performed.The first trial used 4.3 mm diameter glass molds wrapped with four zirconium foil thicknesses; 12 µm, 25 µm, 50 µm, and 125 µm. By varying the foil thickness not only is the minimum amount of non-fissile zirconium determined, but also the physical limitations associated with handling of the foil were better determined. After the optimal thickness was determined based on which pin held its shape better, a foil oxidation study was performed. During the minimum foil thickness study it was observed that fuel alloy would often infiltrate between the overlapping sections of foils and evidence of interaction (metallurgical bond formation) was seen. In order for the foil to unwrap as the fuel swells a metallurgical bond is not desired.To impede this bonding a series of castings were done using zirconium foil that was heat treated in an air atmosphere at 650°C for 1 hour to form an oxide layer. Both 25 µm and 50 µm foils were heat treated.An added benefit of heat treatment and oxidation is the heat treatment stiffened the zirconium foil.When the foil is stiffer, it better maintains its structural integrity and is less susceptible to physical damage from the molten fuel. This prevents potential pathways for the molten fuel to escape the foil from developing. Based on the results of casting into the pre-oxidized foils, a final set of experiments was performed in which 50 µm foil was formed, heated to 650° C for 1 hour in air, and the interior surface coated with a ZrO2 slurry to further prevent interaction. Accomplishments: Four U-10Zr pins were cast using different thickness of zirconium foil. Table 1 shows the mass of the cast material, initial zirconium weight percent, thickness of the foil, the weight percent of zirconium liner (essentially raising the zirconium content of the fuel), and finally the total fuel length cast. As seen in Table 1, the thickness of the foil can be a substantial contributor to the overall amount of zirconium, therefore, minimizing the foil thickness is desirable. During the assembly of the molds it was noted that the 12 µm foil is much harder to load into the quartz mold, because it deforms easily Fabrication of fuel incorporating integral zirconium FCCI barriers has been optimized to point where irradiation testing is feasible.