Fault Reactivation Induced by Temperature and Pressure Changes in the Life of a Deep Geological repository.

The potential of inducing fault reactivation by a synthetic nuclear waste repository in a clay-stone formation is here investigated. The target clay formation may be expected to be almost impermeable, having self-healing and long-term plastic properties, to make sure the canisters, loaded with high-level radioactive waste, are confined and kept in place, with no migration of radionuclides from the storage tunnels. However, in the initial phase of the storage, the radionuclide decay is responsible for a sharp increase in temperature of ~100°C, expected to peak after about 10-100 years. Concurrently, a fluid pressurization of up to ~10MPa is predicted to peak around 1000-5000 years as a consequence of a temperature increase as high as 20°C in a larger volume surrounding the repository.