Ion Exchange Column Testing for Iodine Sequestration from Hanford Low-Activity Waste and Its Impacts on Waste Form Performance

The management of radioiodine during the disposal of nuclear wastes presents a continuing challenge due to its long half-life and high environmental mobility. Strategies to mitigate these challenges include management of radioiodine inventories through sequestration from primary waste streams using ion exchange resins or improvements to candidate waste forms. This work focuses on coupling these two approaches for radioiodine in both waste treatment and waste forms. A series of column tests were performed in simulated low-activity waste (LAW) from the U.S. Hanford site to assess the ability of a strong-base anion ion exchange resin to remove iodide with varying column sizes and superficial velocities. Column performance was strongly dependent on hydraulic operating conditions, with improved breakthrough performance observed at lower flow rates and superficial velocities. A column test with an actual Hanford tank waste sample (from tank 241-AP-101) highlighted that differing waste chemistry had little impact on resin performance compared to a previous waste test. The effluent from a column test of actual Hanford tank waste was immobilized as a cementitious waste form, and in a first-of-its-kind demonstration, the addition of a Ag-amendment to a cementitious waste form prepared with actual Hanford tank waste led to marked improvement in iodine retention. This work further matures two candidate approaches for iodine mitigation in the processing and immobilization of nuclear wastes containing iodine.