Temperature Comparisons of Cesium Ion Exchange Performance with Crystalline Silicotitanate on Hanford Tank Waste - 22018

Crystalline silicotitanate (CST) ion exchanger is planned to be used to remove cesium (¹³⁷Cs) from the aqueous phase of Hanford tank wastes in preparation for vitrification at the Waste Treatment and Immobilization Plant (WTP). The average bulk supernate temperatures of the majority of the double-shell tanks (DSTs) in the tank farms currently average around 16 deg. C during the spring and winter months. Column testing with simulants and actual tank waste were conducted at 16 deg. C and 25 deg. C to test the impact of operating temperature on ion exchange processes. With a decrease in temperature, CST capacity for Cs increased while the kinetics of the exchange decreased. Cesium exchange kinetics were more heavily impacted by temperature than CST particle size during ion exchange processing of AP-107 tank waste at 16 deg. C. Based on these results, a determination of temperature impacts on overall mass transfer will allow future modeling of breakthrough performance at a range of process conditions. (authors)