MECHANICAL-PROPERTIES OF (U,CE)O-2

Ultrasonic pulse echo and Vickers hardness measurements were performed to estimate the mechanical properties of single crystal UO2 and sinte red (U,Ce)O-2 with various porosities. From the sound velocities obtai ned for single crystal UO2 and sintered (U,Ce)O-2, the Young's and she ar moduli and Poisson's ratio were estimated. The Young's and shear mo duli and Poisson's ratio decreased with the CeO2 content. By careful m easurements with various loads, the Vickers hardness of 100% dense (U, Ce)O-2 (porosity 0%) was obtained. The value for 100% dense UO2 was in goad agreement with the hardness of single crystal UO2. The Vickers h ardness of (U,Ce)O-2 also decreased with the CeO2 content, irrespectiv e of porosity (0 and 14% porosity). There is a good correlation betwee n the Young's modulus and the Vickers hardness obtained for (U,Ce)O-2 irrespective of porosity. The yield stress of (U,Ce)O-2 evaluated from both the Young's modulus and the Vickers hardness decreased with the CeO2 content. The diagonal of the radial crack of UO2 single crystal w as also measured, and the fracture toughness K-c was estimated to be 1 .1+/-0.2 MPa m(1/2). (C) 1998 Elsevier Science S.A.