[en] This research thesis deals with the prediction of the failure of a pressurized water reactor under an accidental thermo-mechanical loading. This study is based on tests performed on an instrumented mock-up and on the comparison of experimental results obtained on two different 16MND15 steel grades with numerical simulation results. The test model is a tube submitted to tension and inner pressure. Temperatures, strains and pressure are measured and images are acquired by two rapid digital cameras and an infrared camera. Crack initiation and propagation conditions are acquired. Simulations are performed using finite elements and the ABAQUS code. Crack initiation and growth are modelled by a cohesive area method. Strain rates are also studied