b'Figure 3. Example nanoindentation creep experiment on (U70,Ce30)O 2specimen using an in-situ heater at 800 C. The value circled is the stress exponentof the compound.samples that were 3 mm in diameter3, which shows the natural log of by 3 mm thick. The representativethe strain rate as a function of the UO 2data and reference 10 mm UO 2 natural log of the stress. During stead thermal diffusivity data are shown instate creep, an exponential behavior is Figure 2. The UO 2thermal diffusivityexpected, allowing extraction of the data is within 6% of the referencestress exponent. This was determined data, while the U 3 Si 2was withinfor multiple concentrations CeO 2in 10-15% of the reference values.(U,Ce)O 2 . Stress exponents ranged The uncertainty is largely tied to thefrom 5-7, which is within the carbon coating, which is requireddislocation flow regime at 800C. to improve energy absorption andBoth measurements techniques will surface emissivity. While normally aprovide methods to extract valuable negligible effect for standard sizeddata on irradiated samples after pellets, the smaller geometries willaccelerated test irradiations.require corrections to account forReferences:the contributions to diffusivity from[1.] Petrie, C.M., Burns, J.R., Raftery, the coating. Nanoindentation creepA.M., Nelson, A.T., Terrani, K.A., measurements were also performedJournal of Nuclear Materials, 526 on (U,Ce)O 2in a high temperature(2019) 151783.in-situ nanoindenter stage to 800C. Results for this are shown in Figure 2020|AFC ACCOMPLISHMENTS 49'