Determining the dissolution rates of actinide glasses: A time and temperature product consistency test study

This paper addresses the composition, relative durability, and dissolution rate characteristics of the actinide glass, Loffer Target, that will be used in the Americium/Curium Vitrification Project at the Savannah River Plant. The first part of the paper discusses Product Consistency Tests (PCTs) performed on the Loffler Target Glass to determine dissolution rates. A total of 47 tests were performed on the Loffler Target, water blanks, and an Approved Reference Material glass. Results are presented in tabular form and graphically. The second part of the paper discusses experiments performed to determine the activation energy of the Loffler Target glass. PCTs were performed at temperatures from 60 to 210 C. Activation energies were calculated from elemental analyses of the leachates and are presented. The study showed that the concentration of PCT leachate species is both time and temperature dependent. As time increases, the instantaneous dissolution rates decrease following a power law relationship. Loffler Glass is more durable than quartz or fused silica by an order of magnitude. Temperature studies showed a similar result; as temperature increases, the amount of dissolved leachate component increases following an Arrhenius type expression. The pseudo-activation energy for the Loffler Target is around 23 kilojoules/g mole for temperatures below 150 C, and levels off at this temperature