Dehalogenation of electrochemical processing salt simulants with ammonium phosphates and immobilization of salt cations in an iron phosphate glass waste form

Abstract

This study demonstrates the conversion of a simulated salt waste from electrochemical fuel reprocessing into a chemically durable iron phosphate glass waste form through reaction of the salt with ammonium hydrogen phosphate precursors [i.e., NH4H2PO4 and (NH4)2HPO4] and adding Fe2O3. The reaction of the salt simulant ERV2 with the phosphate precursors resulted in dehalogenation of the salt through the production of gaseous NH4Cl and water vapor (plus other minor byproducts) with the residual salt cations incorporating into the iron phosphate glass as oxides. Physical properties and chemical durabilities were measured for iron phosphate glasses made using different salt/phosphate/Fe2O3 ratios. These iron phosphate glasses accommodate high salt cation loadings and have high bulk densities (∼3 × 103 kg/m3), which would provide a high storage volume waste form option (i.e., the volume required to immobilize a given mass of waste). A proof-of-concept demonstration was conducted to show that the NH4Cl off-gas generated during this process reacts with uranium dendrites to directly produce UCl3 that can be recycled as a feedstock for electrochemical processing.