Alpha decay self-irradiation damage in 238Pu-substituted zirconolite

Samples of 238Pu-substituted cubic zirconolite (CaPuTi2O7) were cold-pressed and sintered, then stored at ambient temperature for approx. equal to 200 days. Alpha decay of the plutonium isotope resulted in an accumulated radiation dose of 2.7 x 1025 α/m3. Macroscopic swelling reached a saturation value of 4.7 vol% at this dose, while X-ray dilation saturated at 7 x 1024 α/m3 and an apparent volume increase of 2.2%. The material became X-ray amorphous at 1.3 x 1025 α/m3. A minor amount of microcracking accompanied swelling, but general breakup did not occur. Transmission electron microscopic observations of heavily damaged material indicated a metamict state principally characterized by a highly disordered, electron diffraction-amorphous structure. Fracture surfaces showed a reduction in number of areas exhibiting distinct cleavage at high damage levels, consistent with the disordered structure. (orig.)