Aging effects on curium-doped titanate ceramic containing sodium-bearing high-level nuclear waste

This paper reports that curium-doped titanate ceramic containing sodium-rich high-level nuclear waste showed a gradual decrease in density up to a dose of 8.5 x 1017 α decays · g-1. After that, the rate of density change increased apparently because of crack formation. Optical microscopy showed cracks >0.1 mm long and >1 μm wide after a dose of 7.9 x 1017 α decays · g-1. Leach tests suggested that the dissolution-control phases for sodium and cesium changed from freudenbergite and hollandite, respectively, to intergranular phases after significant cracking. Aging also enhanced strontium losses, relative to calcium, indicating that strontium may also be partitioned to the intergranular phases. After the fresh surfaces produced by cracking were exposed to leachant, and the dissolution of soluble intergranular surfaces was complete, the leaching of nonradioactive elements from the samples having a dose of 12.3 x 1017 α decays · g-1 was limited by the following dissolution-control phases: freudenbergite (Na), hollandite (Cs and Ba), perovskite and/or zirconolite (Sr and Ca), and alloys (Mo)