SUMMARYIon exchange is the leading candidate process for radioactive cesium removal from Hanford's alkaline supernates and dissolved salt cakes. Duolitem CS-100 has been chosen as the baseline material for cesium ion exchange in the Initial Pretreatment Module (PM) conceptual design. A final exchanger down-selection will occur in FY 96 before IPM Title I design. At that time, other cesium exchange materials will'be considered to replace CS-100.This report presents the results of an evaluation of commercially available exchangers to determine which materials warrant further investigation. Only exchangers which are currently in production or which can be purchased by special order have been included in this study.To identify candidate exchangers, representatives from major ion exchange .manufacturers were consulted and literature from the DOE complex was reviewed. The exchangers which were evaluated are shown in Table S. 1. These materials were compared based on the following criteria: (1) cesium distribution coefficient, (2) rate of cesium sorption, (3) elution characteristics, and (4) chemical and radiochemical stability. Each exchanger was compared to the baseline CS-100 resin. Resins with cesium distribution coefficients markedly lower than CS-100 were eliminated from consideration. TABLE S 1. List of Ion Exchange Materials StudiedVery few ion exchange materials show strong cesium selectivity in highly alkaline solutions. Of the eight organic resins studied, only resorcinol-formaldehyde (R-F) and Duolite C-3 resins have distribution coefficients as high or higher than CS-100. All of the zeolite materials were also found to have cesium distribution coefficients of similar magnitude to CS- Although R-F resin has a significantly higher distribution coefficient than CS-100, the elutability and chemical and radiochemical stability of the resin may be a concern. ~u o l i t e~ C-3 has equilibrium behavior similar to CS-100, but information is lacking with regards to mass transfer rate and chemical stability. Furthermore, in the one elution test performed, C-3 showed poor elutability.Zeolites have similar cesium sorption characteristics to CS-100. However, their poor chemical stability in both high caustic and acidic make loading in Hanford wastes and subsequent elution difficult. Furthermore, since no eluants for zeolites are now being considered, the loaded exchanger would be "itrified as high level waste. Studies have shown that excessive amounts of HLW glass would be produced if zeolites were used. Future research should focus on addressing the limitations of these exchangers. The chemical and radiochemical stability of R-F resin should be verified with further testing using the newly available BSC-210 batch of R-F resin. The resin's stability should be studied in the context of the full-scale ion exchange process to determine how significant these problems really are.