Zirconia ceramics for excess weapons plutonium waste

Abstract We synthesized a zirconia (ZrO2)-based single-phase ceramic containing simulated excess weapons plutonium waste. ZrO2 has large solubility for other metallic oxides. More than 20 binary systems AxOy–ZrO2 have been reported in the literature, including PuO2, rare-earth oxides, and oxides of metals contained in weapons plutonium wastes. We show that significant amounts of gadolinium (neutron absorber) and yttrium (additional stabilizer of the cubic modification) can be dissolved in ZrO2, together with plutonium (simulated by Ce4+, U4+ or Th4+) and impurities (e.g., Ca, Mg, Fe, Si). Sol–gel and powder methods were applied to make homogeneous, single-phase zirconia solid solutions. Pu waste impurities were completely dissolved in the solid solutions. In contrast to other phases, e.g., zirconolite and pyrochlore, zirconia is extremely radiation resistant and does not undergo amorphization. Baddeleyite (ZrO2) is suggested as the natural analogue to study long-term radiation resistance and chemical durability of zirconia-based waste forms.