b'Nuclear Science User Facilities In-situ Small-Scale Mechanical Testing of Fast Reactor Mixed Oxide PinsDavid FrazerLos Alamos National Laboratorydfrazer@lanl.govT he sample investigated in theseResultsexperiments belongs to aQualitative inverse pole figures were mixed oxide (MOX) legacy pin,acquired to evaluate the crystal-available in a hot cell at the Hot Fuelslinity of the cfuel samples. The main Examination Facility of Idaho Nationalphase is composed of a solid solu-Laboratory. The pin was irradiatedtion of (U,Pu)O 2 . The small inclu-in the Fast Flux Test Facility betweensions present with different crystal 1985 and 1992. From the sample, fourorientation have either a cubic blocks of size approximately 70 mstructure compatible with (Ba,Zr) 70 m30 m were cut from theO 3phases or hexagonal structure original sample using the FEI Heliostypical of Mo-Ru-Rh-Tc-Pd noble plasma focus ion beam installed at themetal precipitates [1]. The measured Irradiated Materials Characterizationreduced modulus E r(GPa) was Laboratory. Blocks 1 and 2 were cutconverted to elastic modulus E (GPa) close to the central hole of the fuelusing Equation 1:pellet, and Blocks 3 and 4 were cut close to the fuel periphery. The blocks were embedded within precut pockets and welded with Pt in a stainless steel disk of 5 mm diameter that could be mounted in the mechanical testingwhere E (GPa) is the indenter Youngs equipment. The blocks were tested withimodulus and, sand ithe sample and a Hysitron PI 88 scanning electronindenter Poissons ratios, respectively. microscope pico indenter to measureA Berkovich diamond tip was used for both elastic modulus and hardness.the present tests. The Youngs modulus Prior to mechanical testing, electronand Poissons ratios are 1140 GPa and backscattered diffraction (EBSD) data0.07, respectively. Regarding the MOX were collected on the MOX blocks atPoissons ratio, the recommended the Electron Microscopy Laboratory.formula by Martin [2] was used:Nanoindentation was conducted at room temperature in displacement-control mode to 200 nm on the blocks, all under vacuum.where x is the sample deviation from stoichiometry, which was assumed to be the as-fabricated value.72'