Evaluating the residence time for cesium removal from simulated Hanford tank wastes using SuperLig^® 644 resin

Abstract

Batch contact and column experiments were performed to evaluate the effect of residence time on cesium removal from two simulated Hanford tank wastes using SuperLig^® 644 resin. The two waste simulants mimic the compositions of tanks 241-AZ-102 and 241-AN-107 at the U.S. Department of Energy (DOE) Hanford site. A single column made of glass tube (2.7-cm i.d.), which contained ~100 ml of H-form SuperLig^® 644 resin was used in the column experiments. The experiments each consisted of loading, elution, and regeneration steps were performed at flow rates ranging from 0.64 to 8.2 BV/h for AZ-102 and from 1.5 to 18 BV/h for AN-107 simulant. The lowest flow rates of 0.64 and 1.5 BV/h were selected to evaluate less than optimal flow conditions in the plant. The range of the flow rates is consistent with the River Protection Project design for the waste treatment plant (WTP) columns, which will operate at a flow rate between 1.5 to 3 BV/h. Batch contact experiments were also performed for two batches of SuperLig^® 644 to determine the equilibrium distribution coefficients (K _d) as a function of Cs concentration. The column experiments revealed that adequate column loading for Cs on SuperLig^® 644 (50% breakthrough at 100 bed volumes) can be achieved for the two simulated Hanford tank wastes at the nominal plant flow rates of 1.5 and 3 BV/h (residence times 40 and 20 minutes). The column performance was marginally improved at flow rates below the nominal rates. At flow rates higher than the nominal, the Cs loading deteriorated significantly. The SuperLig^® 644 was eluted effectively with 0.5M nitric acid. The elution required approximately 15 BVs to reduce Cs concentration to below 1% of initial Cs concentration in the feeds.