α‐Decay Damage Effects in Curium‐Doped Titanate Ceramic Containing Sodium‐Free High‐Level Nuclear Waste

A polyphase titanate ceramic incorporating sodium‐free simulated high‐level nuclear waste was doped with 0.91 wt% of ²⁴⁴Cm to accelerate the effects of long‐term self‐irradiation arising from α decays. The ceramic included three main constituent minerals: hollandite, perovskite, and zirconolite, with some minor phases. Although hollandite showed the broadening of its X‐ray diffraction lines and small lattice parameter changes during damage ingrowth, the unit cell was substantially unaltered. Perovskite and zirconolite, which are the primary hosts of curium, showed 2.7% and 2.6% expansions, respectively, of their unit cell volumes after a dose of 12 × 10¹⁷α decays.g^‐1 Volume swelling due to damage ingrowth caused an exponential (almost linear) decrease in density, which reached 1.7% after a dose of 12.4 × 10¹⁷α decays.g^‐1. Leach tests on samples that had incurred doses of 2.0 × 10¹⁷ and 4.5 × 10¹⁷ a decays g^‐1 showed that the rates of dissolution of cesium and barium were similar to analogous leach rates from the equivalent cold ceramic, while strontium and calcium leach rates were 2–15 times higher. Although the curium, molybdenum, strontium, and calcium leach fates in the present material were similar to those in the curium‐doped sodium‐bearing titanate ceramic reported previously, the cesium leach rate was 3–8 times lower.