[en] This paper analyzes the capability of a lagrangian fluid-elastic-plastic-dynamics computational method to answer the physical problems of propagation of pressure waves, energy transmission and elastic-plastic deformation in the course of a simulated hypothetical accident in a semplified fast reactor model with a thin wall vessel. On the basis of the experimental data available a physical picture of the mode and effects of energy propagation throughout the system is given, and their interpretation by the computational method is discussed