CHEMICAL SPECIATION OF RADIONUCLIDES MIGRATING IN GROUNDWATERS

In order to more accurately predict the rates and mechanisms of radion uclide migration from low-level waste disposal facilities via groundwa ter transport, ongoing studies are being conducted at field sites at C halk River Laboratories to identify and characterize the chemical spec iation of mobile, long-lived radionuclides migrating in groundwaters. Large-volume water sampling techniques are being utilized to separate and concentrate radionuclides into particulate, cationic, anionic, and nonionic chemical forms. Most radionuclides are migrating as soluble, anionic species which appear to be predominately organoradionuclide c omplexes. Laboratory studies utilizing anion exchange chromatography h ave separated several anionically complexed radionuclides, e.g.,Co-60 and (106)RU, into a number of specific compounds or groups of compound s. Large-volume ultra-filtration experiments have shown that significa nt fractions of the radionuclides are being transported in these groun dwaters in the form of macromolecules having molecular weights ranging from less than 3,000 to 100,000.