Concentration of Radioactivity and Detection of Cobalt-60 and Zinc-65 in Rainout

Abstract

Ion-exchange resins have been used to concentrate, isolate and determine low levels of radioactive contaminants in rainwater. After the particulate and associated activities are removed by filtration, the ionic materials are retained on cation- and anion-exchange resin columns which are arranged in series. This technique lends itself to the concentration of the low-level activities because the filtered rainwater contains a negligible amount of solids. Consequently, a large volume can be passed through the resin columns before the exchange capacity is approached. Gamma scintillometry was used to identify the γ-emitters in each of the components in this concentration study. In addition to the expected fission-product activities in rainout, photopeaks attributed to Co 60 and Zn 65 were discernible. Despite the fact that the activity levels of these nuclides were very low, their photopeaks were considered to be significant. However, for positive identification, quantitative separation was required. A sequential elution scheme based on the anionic adsorption of cobalt and zinc in solutions containing HCl in high concentration was used to separate the cobalt from the zinc, and from other anions adsorbed on the Dowex-1-(C1) resin. Following elution, each nuclide was radiochemically isolated for quantitative measurement.