Behavior of ²³⁸Pu-doped ceramics based on cubic zirconia and pyrochlore under radiation damage

Crystalline ceramics based on durable actinide host phases such as cubic zirconia and titanate pyrochlore have been suggested for the immobilization of weapons grade plutonium and actinide wastes. Samples of crystalline ceramics based on the gadolinia-stabilized cubic zirconia, (Zr, Gd, Pu)O₂, structure doped with 9.9 wt% ²³⁸Pu were synthesized and characterized in comparison with samples of pyrochlore-based ceramic, (Ca, Gd, Hf, U, Pu)₂Ti₂O₇, doped with 8.7 wt% ²³⁸Pu. It was found that a resistance of cubic zirconia to self-irradiation is much higher than that of pyrochlore. At the cumulative dose 1.1x10²⁵ alpha decays/m³, cubic zirconia retained its crystalline structure. No swelling or cracking were observed in the ceramic matrix. At the same cumulative dose the titante pyrochlore became nearly amorphous and the density decreased by approximately 10% in comparison with the initial, unaltered sample. Under self-irradiation, both ceramics demonstrated an increase of normalized Pu mass loss in deionized water depending on cumulative doses, but this increase is significantly greater for the pyrochlore-based ceramic. (author)