2018 | ANNUAL REPORT 117 Figure 5. Time-of-flight measurements of internal swelling distribution in two Block 3 hex-coins. Coin 3D experienced both higher dose and temperature compared to coin 3B. The asymmetry of swelling is the consequence of a gradient in gamma heating rate, moving from right to left. Figure 6. Time-of-flight through- thickness measurements showing the effect of competing effects of carbide densification and void swelling in high-dose Block 3 and low-dose Block 5. Carbide precipitation increases the flight time while void swelling decreases it. Swelling peaks in the hotter center of Block 3.