ALPHA-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 Cm-244 to accelerate the effects of long-term self-irradiation arising from or 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 x 10(17) alpha 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 X 10(17) alpha decays.g(-1). Leach tests on samples that had incurred doses of 2.0 x 10(17) and 4.5 X 10(17) alpha 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 rates 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.