Titanate-based ceramic as a matrix for curium and rare earth element fraction of radioactive waste immobilization

Abstract

The effective isolation of radioactive waste (RW) from the environment is the main problem for the further development of nuclear power. The main phases in titanate-based ceramics are perovskite, rutile, zirconolite and murataite. Murataite grains have a zonal structure with high content of rare earth elements at the center of structure and low content of these at edges, that precludes their leaching in contact with a solution. Murataite-based ceramics containing simulated rare earth elements of high level waste (HLW) were produced via melting of oxide mixtures in a resistance furnace at 1500°C. All samples were composed of mainly murataite and minor perovskite, crichtonite, zirconolite, and pyrophanite/ilmenite phases. Thus, murataite is the dominant host phase for a sample containing zirconium oxide. All samples were analyzed by scanning electron microscopy with an energy dispersive X-ray spectroscopy. Elemental leaching rates from the ceramic with low perovskite content were lower by one order of magnitude then leaching rates for high perovskite content.