Improved polyphase ceramic for high-level defense waste

Modifications of the chemical formulation and processing of the Synroc-D polyphase ceramic for defense waste have been studied to provide greater flexibility with respect to compositional variations in the waste and to improve leach resistance. It has been demonstrated that by applying only that amount of reduction to the waste required to produce uranium in the 4+ state and by using lower consolidation temperatures, an improved ceramic can be formed. The resulting ceramic consolidated at 10400C and 10,000 psi maintanis the Synroc-D zirconolite, perovskite and nepheline phases; however, the two Synroc-D spinel phases are replaced with a single magnetite-type spinel and two additional radiophases, magnetoplumbite, and a cubic murataite-type phase. This modified phase assemblage provides crystalline ost sites for all radionuclides and trace elements in SRP waste, minmizes amorphoous intergranular material, and shows superior leach resistance