Silver-based getters for 129I removal from low-activity waste

A prominent radionuclide of concern in nuclear wastes, I-129, is present in low-activity wastes (LAW) at the Hanford site. Several Ag-containing materials were tested as immobilization agents, or getters, for I (as iodide, I-) removal from deionized (DI) water and a liquid LAW simulant: Ag impregnated activate carbon (Ag-C), Ag exchanged zeolite (Ag-Z), and argentite. In anoxic batch experiments with DI water, the Ag-C and argentite were most effective, with maximum K-d values of 6.2 x 10(5) mL/g for the Ag-C and 3.7 x 10(5) mL/g for the argentite after 15 days. Surface area and Ag content were found to influence the performance of the getters in DI water. In the anoxic batch experiments with LAW simulant, Ag-Z vastly outperformed the other getters with K-d values of 2.2 x 10(4) mL/g at 2 h, which held steady until 15 days, compared with 1.8 x 10(3) mL/g reached at 15 days by the argentite. All getters were stable over long periods of time (i.e. 40 days) in DI water, while the Ag-Z and argentite were also stable in the LAW simulant. Ag-Z was found to have consistent I removal upon crushing to a smaller particle size and in the presence of O-2, making it a strong candidate for the treatment of LAW containing I.