A thermo-hydro-mechanical numerical model for plain irradiated concrete in nuclear shielding

The need for long-term predictions of the performance of old nuclear power plants concrete shielding all around the world has recently relaunched the issue of predictive modeling of the deterioration mechanisms associated to irradiated concrete, both theoretically and numerically. A robust numerical model for describing concrete affected by prolonged nuclear irradiation, based on a coupled thermo-hydro-mechanical formulation, is proposed and the main features that are phenomenologically responsible for the degradation of concrete material at the mesoscale level are discussed. The study is conducted at the mesoscale to account for the antagonist action of the cement paste and aggregates when irradiated. Radiation-induced damage is assimilated to mechanical damage in the proposed formulation in that radiation-induced volumetric expansion of aggregates is conceived as the source of triggering of damage in the surrounding paste. The numerical results for plain concrete samples exposed to severe radiation fluences and high temperature are juxtaposed with experimental data, showing that the model agrees satisfactorily with the general tendency of the irradiated concrete stiffness evolution and dehydrated water mass of the sample. On the other hand, the model tends to underestimate its global radiation-induced volumetric expansion.