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 th e effects of long-term self-irradiation arising from or decays. The ce ramic 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 parame ter changes during damage ingrowth, the unit cell was substantially un altered. Perovskite and zirconolite, which are the primary hosts of cu rium, showed 2.7% and 2.6% expansions, respectively, of their unit cel l volumes after a dose of 12 x 10(17) alpha decays.g(-1). Volume swell ing due to damage ingrowth caused an exponential (almost linear) decre ase 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 d issolution of cesium and barium were similar to analogous leach rates from the equivalent cold ceramic, while strontium and calcium leach ra tes were 2-15 times higher. Although the curium, molybdenum, strontium , and calcium leach rates in the present material were similar to thos e in the curium-doped sodium-bearing titanate ceramic reported previou sly, the cesium leach rate was 3-8 times lower.