Considerations on the behaviour of long-lived radionuclides in the soil

The migration of radionuclides from waste repositories to the biosphere pot entially leads to a contamination of soil. Due to the importance of food pr oduction, the mobilisation and accumulation behaviour of long-lived radionu clides in the soil plays a key role in performance assessment studies. In t his paper, the main features and processes that control radionuclide behavi our in soil, such as pH, redox potential and sorption to organic and inorga nic soil components, are discussed for the radionuclides Cl-36, Se-79,I-129 , Tc-99, Np-237 and U-238, that are usually most relevant in long-tel-m saf ety assessments of nuclear waste. The interaction of radionuclide behaviour in soil with environmental factors, such as temperature and humidity as we ll as farming practices are discussed. The possible impact of future soil d evelopment on long-term behaviour in soil are taken into consideration. Due to the physiological constraints of plant growth, appropriate soil conditi ons for growth will probably not be substantially different from current re quirements, bearing in mind that sustainable agriculture strives for optima l plant growth. Against this background, present-day parameters may in gene ral be considered appropriate for roughly estimating the behaviour of radio nuclides in the soil-plant system.