Long-term laboratory and in-situ migration experiments in Boom Clay – status 2017

This report gives an overview of the long-term migration experiments that were set up in the last three decades. It provides a compilation of all these long-term migration tests, the acquired data and their interpretation. The long-term migration experiments include as well in-situ experiments in the underground research facility HADES at SCK•CEN (Mol, Belgium) as lab-scale experiments (clay cores of 38 mm diameter with varying length). The in-situ experiments involve the radionuclides HTO, iodide, Am, Tc, inorganic carbon (H14CO3-) and organic carbon (14C-labelled organic matter). The long-term lab experiments are/were performed with radionuclides (RN) which have the tendency to form “stable” complexes with natural organic matter (NOM) omnipresent in Boom Clay. Two groups of experiments are considered: the running long-term percolation experiments with Tc, Be, Ni, Zn, Pd, Zr, Am, Cm, U, Pu, Np, Pa including the so-called “sequential clay core experiments” and the running long-term percolation experiments to study the colloidal transport behaviour of NOM (through use of 14C-labelled OM) and of RNNOM (through use of “double labelled” species: 14C labelled OM mixed with Am, U, Pu). In addition, the long-term experiments of Ra, belonging to the group of elements characterized by cation exchange sorption, are taken up in the report. All these experiments are presented in the same way: a description of the experiment with the specific details, an overview of the acquired data, interpretation of the data and the model predictions performed. In the final chapter, a synthesis is made of the general observations and the lessons learned are discussed. Over the decades, new insights were acquired and improvements and adaptations of the experimental set-ups and model calculations were done.