Radioactive waste storage in salt structures under cyclic glacial loading

Various salt structures, such as diapirs and salt walls, are currently considered as potential locations for the long-term storage of radioactive waste. Yet many scientific questions need to be addressed before safety and integrity of such repositories can be ensured. In particular, the effect of cyclic glacial loading on the long-term stability of a potential nuclear waste repository needs to be investigated.

In the first part of this study, we perform a series of simplified 2D thermo-hydro-mechanical model scenarios selected to cover the basic geometrical features of salt diapirs and walls. Our models include internal heterogeneities in the salt and faults in the salt and overburden. We consider various repository design schemes and investigate the effect of the radiogenic heat production on the deformation of the surrounding salt in a thermo-mechanically coupled manner. We explore the sensitivity of the results to variations in the physical rock properties and evaluate the potentially significant effect of the different dominant microphysical deformation mechanisms such as dislocation creep, dynamic recrystallization and pressure solution creep in salt.

The second part of this study focuses on the parameterization of the relevant salt rheology that controls the viscoelastic response of the salt structure. We quantify the rock salt rheology in a probabilistic sense by implementing a statistical creep model. Here, we incorporate a priori constraints and observations from the microstructure and determine representative creep law parameters and associated uncertainties.

Following this integrated approach, we aim to identify key model parameters and find characteristics of generic salt structures to assist the selection process of suitable salt structures.