DIPHONIX-CS - A NOVEL COMBINED CESIUM AND STRONTIUM SELECTIVE ION-EXCHANGE RESIN

The recently developed Diphonix(R) resin contains the geminally substi tuted diphosphonic acid ligand chemically bonded to a styrene-divinylb enzene copolymer. The resin exhibits an extraordinarily strong affinit y for actinides, especially in the tetra-and hexavalent oxidation stat es. Therefore the resin has potential for application in TRU removal f rom nuclear wastes. The Diphonix-CS resin is a Diphonix-type resin tha t contains also phenolic groups chemically attached to the polymeric m atrix. The phenolic groups exhibit high affinity for Cs' ions from hig hly alkaline media. Thanks to the combined action of the diphosphonic acid and the phenolic groups, the Diphonix-CS resin can simultaneously remove actinide species, Cs and Sr from alkaline media. In this paper the results obtained in the characterization of the new resin are rep orted, with regard to the uptake equilibrium and kinetics of Cs+ and S r+2 removal from NaOH solutions and from synthetic alkaline wastes. Th e chemical and radiolytic stability of the resin has been investigated . The results have indicated that the Diphonix-CS resin is remarkably stable under the experimental conditions of this work (up to 35 days i n 1 to 4 M NaOH, and up to 200 MRad gamma ray absorbed dose). The poss ibility of stripping the Cs+ and Sr+2 from the resin has been investig ated in column experiments by using 1 M HNO3 as the stripping agent. S ome problems encountered in the stripping of Sr+2 and possible ways to improve the stripping performance are discussed.