GLOBAL CHARACTERIZATION OF KEROGEN FROM THREE ARGILLACEOUS FORMATIONS : OLIGOCENE (MOL, BELGIUM), CALLOVO-OXFORDIAN (BURE, FRANCE) AND TOARCIAN (TOURNEMIRE, FRANCE)

摘要

Deep argillaceous formations are potential long-term nuclear waste repositories because of their low permeabilities and high sorption capacities with respect to radioelements and heavy metals. Three argillaceous formations are considered in this study: a plastic one (Oligocene) selected in Belgium (Mol) containing 3 percent w/w of organic matter and two consolidated ones (Callovo-oxfordian and Toarcian) selected in France (Bure and Tournemire respectively) containing around 1 percent w/w of organic matter. For the three rocks, organic matter is mostly insoluble (kerogen). Upon temperature elevation related to a high-activity waste disposal, kerogen may release significant quantities of gaseous and liquid effluents. The latter may affect the efficiency of the geological barrier through modification of the physico-chemical parameters (e.g. pH, ionic strength, pressure). Previous studies [1, 2] performed on Mol rock have shown the capacity of its kerogen to release O-containing compounds even at unusually low temperatures. Their complexation properties may thus play a major role in the retention or migration of the radionucleides.