2017 | AFC ACCOMPLISHMENTS 75 of U3Si2 and other U-Si compounds found that hydrogen atmospheres produced poor results. It is now known that this was caused by hydriding of the U3Si2 feedstock at low temperatures.Work here used standard argon at low temperatures before switching to a 6%H2/Ar mix at 1000°C. Hydrogen was removed from the furnace prior to cooling. The results are summarized in Figure 2, where laser flash analysis data is presented. Both vacuum and hydrogen pellets are slightly less dense than the reference data (approx. 90% theoretical density) which accounts for much of the difference in thermal diffusivity.The vacuum sintered material showed similar diffusivity to the reference Ar sintered pellet when corrected for density, while the sample sintered in 6%H2/Ar displays hysteresis at temperatures below 400°C.This is presently attributed to microcracking induced by minor hydride forma- tion caused by incomplete removal of hydrogen from the system, but further work is needed to substantiate this hypothesis. Figure 2. Characterization of the thermal diffusivity for pellets of U3Si2 sintered in Ar (reference), vacuum, and 6%H2/Ar.