The role of phosphate released from Na–Al–P glass under repository conditions in speciation and transport of americium

Interactions of components of the multibarrier safety system of an underground repository environment are important factors for safety assessments. Na–Al–P glass is the major high level waste (HLW) matrix in Russia. Degradation of HLW glass causes an increase of phosphate concentration in water that influences on radionuclides speciation. Americium is important in HLW. In the presence of phosphate in synthetic groundwater almost half of the americium present is in colloidal matter and its sorption onto clay is slightly decreased relative to the absence of phosphate. The presence of phosphates in the system of synthetic groundwater—clay during sorption experiments significantly affected on the solid-phase speciation and led to an increase in the proportion of strongly bound americium.