Fundamental Thermodynamics of Actinide-Bearing Mineral Waste Forms

The landmark record of decision in January 2000 by the US Department of Energy stated that at least 17 tons of surplus weapons plutonium will be converted to a mineral waste material and disposed of in a geological repository similar to the proposed Yucca Mountain nuclear waste site in Nevada. The need for fundamental thermodynamic properties (e.g., entropy, enthalpy and free energy of formation) of specific actinide-bearing mineral phases, related non-actinide phases, and potential decomposition phases is vital to waste material formulation, fabrication process optimization, environmental modeling, and licensing a proposed mineral waste material. Two and one half years ago we began a study designed to obtain the first measured values for the formation energetics of phases related to the disposal of this surplus weapons plutonium