Reactions of a prototype nuclear-waste ceramic with a hot magnesium-rich brine

Prototype ceramic nuclear waste forms have been experimentally reacted with a high calcium and magnesium brine under hydrothermal conditions. The said reaction products and fluid were analyzed at the end of the experiment. Alteration of the waste forms was observed and the reaction products identified. Uptake of cesium, rubidium, strontium, barium, lanthanum and neodymium into the brine was measured with a strong temperature dependence, i.e., increased concentrations with increased temperature. The concentrations of the six elements also increased with time, and imply that dissolution of the ceramic is controlled by diffusion and/or crystalline dissolution mechanism. 20 figures, 18 tables.