Ultrasonic measurement and first-principle calculation on elastic constants of (U,Pu)O

Sakurahara, Tatsuya; Tanaka, Satoru*; Kato, Masato   ; Uchida, Teppei; Uno, Hiroki*

Elastic constants of 20% Pu-containing MOX sintered pellet were measured by ultrasonic pulse echo method as a function of porosity and O/M ratio. In addition, the effects of O/M ratio on elastic constants and its atomic scale mechanism were investigated based on the modeling by first-principle calculation which was performed on Ce-O system as a surrogate material of MOX. Measured Young's and shear moduli decreased linearly as the porosity increased in the range from 5% to 15%, where as poison's ratio remained almost constant. Young's and shear moduli of non-stoichiometric samples (O/M = 1.973 and 1.963) decreased slightly from stoichiometric sample (O/M = 2) by less than 5%, which was in a fairly good agreement with first-principle calculation on Ce-O system. Computational results by first-principle calculation indicated that O/M ratio effect on Young's modulus was dominated by the contribution of chemical lattice expansion.