[en] This paper describes the principles and examples of applications of an explicit Lagrangian coupled finite difference-finite element code HEMP-ESI developed in order to calculate the structural consequences of hypothetical core disruptive accidents (HCDA) in nuclear reactors. The explicit solution algorithm of the finite difference scheme used to discretize the hydrodynamic fluid domains is shown to be very similar to that used for the solution of the finite element discretized shell structures, hence permitting an easy and efficient coupling. Two examples of simulation show the applicability of the method to nuclear reactor core safety analysis (test problem). Core explosion in a loop-type reactor including a shell containment: the calculation shows the energy absorbing function of the shell and enables the evaluation of the forces acting on the reactor containment. Hypothetical Core Disruptive Accident in a fast breeder reactor: the calculation shows the main features of this accident: lifting of the liquid sodium above the explosion and impact on the cover head inducing upward deformations; radial outflow of the sodium which induces large deformations of the inner and outer shell; zones of compressive circumferential stresses in the main shell at the junction of the spherical head and the cylindrical part