Recommendations for performing radionuclide sorption experiments

In order to perform sorption experiments in a standardized way, recommendations for performing sorption experiments with radionuclides (RN) on clayrocks or its constituents (e.g. pure clay minerals, organic matter,…) were formulated. The recommendations are based on the OECD guideline (nr 106) ‘Sorption – Desorption Using a Batch Equilibrium Method’ (OECD, 2000), aiming at estimating the adsorption/desorption behaviour of a substance on soils, on the experience and knowlegde we have built up at SCK•CEN over the years and on the publications of Bradbury and Baeyens from PSI-LES. The guidelines for sorption modelling are based on the NEA publications (NEA 2001, 2005 and 2012). After explaining how the degree of sorption can be expressed and the general approach of a sorption experiment, recommendations are given for the different components of the sorption experiment: the sorbent, the background solution and the test substance. Further, the requirements for the sorption experiment are amplified and a standard stepwise experimental procedure is proposed. In addition, a brief overview of the different factors that can influence the sorption behaviour, the analytical methods and error propagation are illustrated. At last, a brief description on how to model sorption experiments what is needed for this modeling is given.