Effects of heat production in underground radioactive waste repositories

Abstract:

The decay of radionuclides in high-level nuclear waste generates heat, raising the temperature within repository tunnels, their linings, and the surrounding rock. The differential thermal expansion of pore water and ground in combination with the low permeability of host formations such as Opalinus Clay in Switzerland or COx claystones in France, results in the development of excess pore pressures. Hydro-fracturing is a well known adverse effect of thermal pressurisation. The presentation is about two other, less investigated, potential hazards: lining overstressing and shear failure. Coupled stress and seepage flow analyses considering the effects of heat transfer provide an indication that thermal pressurisation can lead to substantial loading and stresses on the tunnel linings within a few decades, calling into question the suitability of conventional, practically rigid linings. Furthermore, depending on rock strength, in-situ stress and increase in temperature, shear failure of the host rock may occur in the far field (outside the EDZ) even if the increased pore pressure does not suffice to induce hydro-fracturing

Short bio:

Dr. Maria Anthi is a Postdoctoral Researcher at ETH Zürich, Switzerland, in the Department of Civil, Environmental, and Geomatic Engineering, under the Chair of Underground Construction at the Geotechnical Engineering Institute. She holds a PhD in Soil Dynamics, an MSc in Analysis and Design of Earthquake-Resistant Structures, and a Bachelor’s degree in Civil Engineering from the National Technical University of Athens (NTUA), Greece. Her research focuses on geotechnical earthquake engineering, soil dynamics, and underground construction, bridging theoretical and applied aspects. She has contributed to major projects, including the Gibraltar Strait Tunnel and Switzerland’s national program for radioactive waste disposal (Nagra). Dr. Anthi has published extensively in peer-reviewed journals and conference proceedings and has been recognized with scholarships and sponsorships for academic excellence.