Abstract and subjects
Continuing to refine our knowledge of the evolving mechanical properties of nuclear fuel over the entire fuel service cycle is necessary to understand the pellet-clad mechanical interaction that occurs in the fuel rods during the operation. A challenge with measuring the mechanical properties of irradiated fuels is their high levels of radioactivity that usually require the use of hot cells making testing time consuming and expensive. Nanoindentation based techniques can be employed on minute volumes of material to measure mechanical properties, including Young ' s modulus, hardness, and creep stress exponents. Increasing the mixed oxide fuels mechanical properties database through a variety of testing techniques should enhance modelers ' abilities to predict failure mechanisms in the fuel/clad interface. A current challenge to testing mixed oxide fuels is the plutonium component in the fuel. Mixed fluorite type oxides with ceria (CeO 2 ) can be used as a surrogate for mixed oxide fuels. In this study, (U,Ce)O 2 solid solutions samples are used to develop elevated temperature nanoindentation and nanoindentation creep testing methods for use on mixed oxide fuels. Nanoindentation testing was performed on 3 separate (U x-1 ,Ce x )O 2 compounds ranging from x equals 0.1 to 0.3 in equal steps at temperatures up to 800 degrees C: their Young ' s modulus, hardness, and creep stress exponents were evaluated. The Young ' s modulus decreases in the expected linear manner while the hardness decreases in the expected exponential manner. The nanoindentation creep experiments at 800 degrees C give stress exponent values, n = 4.7 - 6.9, that suggests dislocation motion as the deformation mechanism.