High-sodium waste streams stabilized with inorganic acid–base phosphate ceramics fabricated at room temperature

A method to stabilize liquid high-sodium waste streams with chemically bonded phosphate ceramics (CBPCs) is presented in this paper. Waste form samples based on CBPC were prepared by mixing a sodium-based waste simulant with calcined magnesium oxide (MgO) and Class C fly ash as filler. The microstructure was identified with X-ray diffraction and electron microscopy. Compressive strength was evaluated for the compositions in which a solid material was obtained. Of the 15 different simulated waste form compositions fabricated, only a few of them did not set into a ceramic material. Immersion tests were conducted over selected compositions. All phases were identified in the solid materials. Results showed that a maximum concentration of 60 wt% NaH2PO4 was attained in the set product showing that CBPC is a promising material for encapsulation of high-sodium nuclear waste.