Elastic and Anelastic Response of Polycrystalline UO 2 ‐PuO 2

A sonic resonance technique was used to investigate the room‐temperature elastic and anelastic properties of physically mixed U 0.8 PU 0.2 O 2 as a function of density, stoichiometry, and cation homogeneity. The effect of porosity on the elastic moduli was linear and is described by E =2102.7 (1–2.03 P )± 13.5 Kbars for the Young's modulus, G =823.5(1–2.05 P )± 9.1 kbars for the shear modulus, and B = 1584.8(1–1.89 P )± 59.1 kbars for the bulk modulus, where P is the volume fraction porosity. Poisson's ratio was 0.28 and was not a function of porosity. The Debye temperature of U 0.8 Pu 0.2 O 2 computed from the Young's and shear moduli for theoretically dense specimens was 379°K. Variation of the O/M ratio from 1.968 to 2.006 produced no significant change in either the damping capacity or the elastic moduli of single‐phase 80%UO 2 ‐20% PuO 2 solid solutions. An approximate 24% decrease of the room‐temperature Young's and shear moduli and an approximate increase by a factor of 14 in the internal friction were observed with gross modifications of plutonium cation homogeneity. Preliminary results suggest that internal friction measurements might be used to assay the homogeneity of UO 2 ‐PuO 2 solid solutions.