Understanding the elementary mechanisms at the origin of glass alteration is very important in the nuclear field because in France nuclear glasses are intended to be stored in a deep geological repository. Consequently, they must be highly resistant to the underground water in order to limit the release of radioelements into the environment. One way to extrapolate the long term behavior of nuclear glasses is to build models based on the elementary mechanisms. In this presentation, a study was performed to better understand the mechanisms of bond hydrolysis and reformation around the Si and Al atoms in SiO2-Al2O3-CaO glasses in contact with water will be detailed. Firstly a diffuse charge reactive potential (DCRP) was developed using a Force Matching technique to reproduce ab initio calculations. This potential has been further refined to better reproduce the experiments [1]. Then this potential has been used to measure the hydrolysis and reformation energies around the Si atoms in pure silica and around the Si and Al atoms in different SiO2-Al2O3-CaO glasses. It was observed that there is a strengthening effect on the Si-O bonds when Al2O3 is added to the glass. Indeed, the Si-O bonds average hydrolysis energy increases from 1.22eV in pure silica to 1.34eV in an aluminosilicate glass. In parallel, it was observed that the Al-O bonds average hydrolysis energy is lower (0.49eV). Moreover, reforming bonds around the Si atoms in aluminosilicate glasses is easier than in pure silica. This effect of Al on the Si-O hydrolysis energies were qualitatively confirmed experimentally [2]. When more complex glasses containing both CaO and Na2O are considered, a non linear effect is evidenced, i.e. the Si-O bonds hydrolysis energy presents a minimum in glasses where CaO and Na2O are mixed. From this observation, it was concluded that the average hydrolysis energy of Si-O in a SiO2-Al2O3-CaO-Na2O glass results from both a chemical effect (the impact of Al) and a topological effect (the level of disorder).