b'Figure 2. A plot of the nanoindentation hardness versus temperature of the 4 materials tested.700 C, as it is not radioactivetested in a reducing environment of and not air-sensitive followed byargon+6% hydrogen it is believe, ThO 2as it was radioactive andthat the UO 2is stoichiometric.not air-sensitive. While the ThO 2 Lastly, U 3 Si 2was measured up to is not air-sensitive it was tested in200 C in an argon environment. an argon atmosphere to evaluateU 3 Si 2was only measured to 200 C the environmental control of theas the specimen oxidized at elevated nanoindenter chamber and introducetemperatures evidenced by the the radiological hazard. After, theincrease in hardness from the surface UO 2was measured up to 700 C as itoxide formation. The U 3 Si 2was was radioactive and ai-sensitive. Themeasured in an argon environment UO 2was measured in an argon+6%instead of an argon+6% hydrogen hydrogen cover gas environmentto prevent hydride formation in in order to inhibit the oxidation ofthe U 3 Si 2 . Additionally, methods of the sample. Due to the UO 2beinginhibiting the oxidation of the U 3 Si 266 2019|AFC ACCOMPLISHMENTS'