Characterization of Radionuclide-Chelating Agent Complexes Found in Low-Level Radioactive Decontamination Waste: Literature Review

摘要

The U.S. Nuclear Regulatory Commission is responsible for regulating the safe land disposal of low-level radioactive wastes that may contain organic chelating agents. Such agents include EDTA, DTPA, picolinic acid, and citric acid, which can form radionuclide-chelate complexes that may enhance the migration of radionuclides from disposal sites. Data from the available literature indicate that chelates can leach from solidified decontamination wastes in moderate concentration and can potentially complex certain radionuclides in the leachates. The effects of the formation of such radionuclide-chelate complexes on the migration of radionuclides in groundwater systems is still difficult to quantitatively predict. However, in general it appears that both EDTA and DTPA have the potential to mobilize radionuclides from waste disposal sites because such chelates can leach in moderate concentration, form strong radionuclide-chelate complexes, and can be recalcitrant to biodegradation. It also appears that oxalic acid and citric acid will not greatly enhance the mobility of radionuclides from waste disposal sites because these chelates do not appear to leach in high concentration, tend to form relatively weak radionuclide-chelate complexes, and can be readily biodegraded. In the case of picolinic acid, insufficient data are available to make definitive predictions.