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The storage or disposal of nuclear waste is one of the major concerns faced by governments, communities, and environmentalists. This radioactive waste, as a source of ionising radiation, represents a potential hazard to human health and must be carefully managed so as to reduce the associated risks to acceptable levels for both now and in the future. The migration of radioactive waste (radionuclides) in the environment is controlled by many factors, such as the interaction of the radionuclides with soil. Humic acid (plant material) has substantial chelating properties for metal ions and can therefore considerably affect the migration behaviour of radionuclides in a soil layer. To manage the radioactive waste effectively, it is important to know the presence and interaction of humic acid with radionuclides released from radioactive waste repositories. The aim of this study is therefore to investigate the influence of humic acid on the distribution coefficients of radionuclides found in both Thabana and Vaalputs waste repositories. The technique employed in this study is based on a laboratory batch method to study the influence of humic acid on the distribution coefficients of (131)^I and (137)^Cs on soil samples from Thabana and Vallputs waste repositories at different concentrations. The results of this study show that (131)^I and (137)^Cs do not form any complexes with humic acid and therefore the presence of humic acid does not have a significant effect on the migration of (131)^I and (137)^Cs. / MSc (ARST) North-West University, Mafikeng Campus, 2005