Boom Clay mineralogy – qualitative and quantitative aspects. Status 2011.

In preparation of the safety and feasibility case 1 for the geological disposal of high-level and long-lived radioactive waste in Belgium, the Boom Clay is studied as the reference host rock. The detailed characterisation of the Boom Clay properties is required to understand the geochemical environment and transport properties within the host rock, as they should ensure the delay and attenuation of the releases of radionuclides, by limited water flow through the system (safety function R2) and retarded contaminant migration (safety function R3). An important parameter is the mineralogical composition of the Boom Clay. This report gives a brief overview of mineralogical studies performed within the past decennia on Boom Clay in various outcrops and boreholes in the Campine Basin, and highlights the new and improved methodology that has been applied recently to qualitatively and quantitatively characterise the mineralogical composition of the Boom Clay. A new methodological approach resulted in, what we believe, a reliable reference of the Boom Clay mineralogy at the reference site of Mol. A compilation of the available data from various boreholes within the Campine basin allowed for a regional comparison of the Boom Clay mineralogical composition in NE-Belgium.