Analysis of Spent SuperLig® 644 Resin used for Cesium Removal from Hanford Tank Wastes

Abstract

The U.S. Department of Energy is tasked with the disposition of alkaline, high‐level radioactive wastes stored in underground tanks at the Hanford Site. The radioactivity of the liquid waste fraction is dominated by the 137Cs and 90Sr fission products. The waste is to be vitrified following specific pretreatment processing, separating it into a relatively small‐volume high‐activity waste fraction (cesium‐rich), and a large‐volume low‐activity waste fraction (cesium‐depleted) at the River Protection Project‐Waste Treatment Plant. The baseline pretreatment flowsheet includes cesium removal using ion exchange technology with SuperLig® 644. After several process cycles, SuperLig® 644 is intended to be disposed of at a radiological waste burial site. Although SuperLig® 644 has been extensively studied with respect to cesium load and elution properties, relatively little is known about the relevant waste characteristics of the spent resin. Small‐column testing was recently conducted through eight process cycles of simulated and actual Hanford tank wastes. The post‐processing SuperLig® 644 resin provided a unique material to evaluate residual metal and radionuclide components remaining on the resin. Most metal constituents and radionuclides pertinent to land disposal requirements designation were measured on dissolved resin sub‐samples. The spent resin was found to contain significant quantities of Resource Conservation Recovery Act‐listed metals: silver and chromium. In addition, one of the two resin beds exceeded the transuranic waste limit (100 nCi/g total alpha activity) for land disposal. The spent resin Cs isotopic distribution was weighted heavily with the Cs of the first waste processed.