Structural And Mechanical Property Changes Under Ballistic Effects In Borosilicate Glasses: A Classical Molecular Dynamics Study

In France, nuclear glasses used to confine long lived actinides are aimed to be stored in a deep geological repository. Then it is important to guarantee their radiation resistance, in particular under the nuclear energy deposition which is responsible for the macroscopic property changes: decrease of the hardness, increase of the fracture toughness. To better understand the origin of these modifications, classical molecular dynamic simulations have been performed on simplified nuclear glasses (SiO2-B2O3-Na2O). The ballistic effects have been first investigated on structures prepared with various initial densities. After the accumulation of displacement cascades the irradiated structures coverage towards each other with a partial removal of the initial shifts. Then, crack propagation has been modelled by applying an external tensile stress on a pristine and a disordered structure prepared with a high quench rate to reproduce the radiation effects. The increase of the plasticity associated with the glass depolymerization was shown to be responsible for the increase of the fracture toughness. Concerning the hardness, its decrease after irradiation has been correctly reproduced by the molecular dynamic simulations and correlated to the structural modifications at the atomic scale.