LA-6529 UC-25 Issued : April 1977 Mechanical Properties of 23 S Pu 0 2 by

The mechanical properties of < Pu02 have been examined in the Los Alamos Scientific Laboratory mechanical test facility built to handle uradioactive materials. Compression tests were conducted as a function of temperature, strain rate, grain size, density, and storage time. At temperatures £14OO°C, test specimens of "PuO2 exhibit pseudobrittle behavior due to internal cracks. Plastic deformation is "localized" at the crack tips. Generalized plastic deformation is observed at 1500°C. Ultimate stress values decrease markedly with increasing temperature and decreasing strain rate, and decrease less with decreasing density, increasing storage time, and increasing grain size. Room temperature fracture is transgranular, whereas intergranular fracture predominates at elevated temperatures. Crack-free specimens of PuO2 exhibit extensive plastic deformation at 1000° C and above. The relationship of these test results to the impact properties of PuO2 fuel in radioisotope thermoelectric generators is discussed.