Americium Concentrations in Solutions Contacting Americium-Doped Glass

Americium-doped glass (0.053 wt% 241Am) was contacted with dilute salt solutions (0.001 MNaClO4), pH buffers, Permian Basin brine (PBB1), and tentimes-diluted PBB1 to determine the aqueous americium concentrations that can be expected in equilibrium with this glass. The americium concentrations in all of these solutions were similar and decreased with increasing pH; americium concentrations decreased to the detection limit (∼10−11.6M) at a pH value of ∼7 and remained at or near the detection limit at pH values >7. Americium concentrations in glass suspensions with pH >5 were found to be controlled by the dissolution of an americium-solid. The value of the log of the equilibrium constant for the solubility of this americium-solid (Am-solid+3H+ = Am3++ H3-solid) was determined to be ∼10.3. The americium-solid is found to effectively control aqueous americium to very low concentrations under slightly acidic to alkaline conditions. The high ionic strength and the high Cl−concentrations in brine are found not to measurably affect the americium-solid solubility.