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

Abstract

The migration of radionuclides from waste repositories to the biosphere potentially leads to a contamination of soil. Due to the importance of food production, the mobilisation and accumulation behaviour of long-lived radionuclides in the soil plays a key role in performance assessment studies. In this paper, the main features and processes that control radionuclide behaviour in soil, such as pH, redox potential and sorption to organic and inorganic soil components, are discussed for the radionuclides 36Cl, 79Se, 129I, 99Tc, 237Np and 238U, that are usually most relevant in long-term safety assessments of nuclear waste. The interaction of radionuclide behaviour in soil with environmental factors, such as temperature and humidity as well as farming practices are discussed. The possible impact of future soil development on long-term behaviour in soil are taken into consideration. Due to the physiological constraints of plant growth, appropriate soil conditions for growth will probably not be substantially different from current requirements, bearing in mind that sustainable agriculture strives for optimal plant growth. Against this background, present-day parameters may in general be considered appropriate for roughly estimating the behaviour of radionuclides in the soil-plant system.

The Geochemistry of Technetium: A Summary of the Behavior of an Artificial Element in the Natural Environment

“…This table also lists the corresponding biogeochemical zones (Burke et al 2005). The kinds of redox reactions that take place in each are as follows (Koch-Steindl and Pröhl 2001). For normal soil, NO 3 -reduction begins between 550 to 450 mV, while Mn 2+ formation is initiated between 450 to 350 mV.…”

Effects of freezing and soil drought on the geochemical fractionation of americium in Fluvisol and Cambisol soils from Bulgaria

“…Schultz et al 1998;Rao et al 2008), which depends both upon their physicochemical forms and the soil characteristics (Igwe et al 2005). The long-term differences of the environmental conditions were found to cause redistribution of the radionuclides within the various soil fractions due to changes of the pH, the redox potential, destruction of the organic matter, leaching and ion-exchange (Koch-Steidl and Pröhl 2001). Sharp variations of environmental temperature can influence the amount and the rate of radionuclide adsorption to soil particles.…”

Natural iodine in a clay formation: Implications for iodine fate in geological disposals

“…Iodine can be found in an elemental form I 2 (valence 0), as iodide I -(-1) or iodate IO 3 -(+5). Its fate and transport are dictated by its chemical speciation (Koch-Steindl and Prohl, 2001). In the following, when the redox state cannot be specified, the notation iodine* will be used.…”