[en] The explicit 2-D axisymmetric Lagrangian code SIRIUS, developped in CEA Cadarache, is able to deal with transient compressible flows in deformable primary tanks with complex geometries of internal components. The ultimate objective of this code is to perform the analysis of SUPER-PHENIX reactor integrity when subjected to transient loads resulting from an HCDA (Hypothetical Core Disruptive Accident). This paper described the basic equations for fluids and thick elastic-plastic media, the shells modelling and the fluid-shell coupling. As an illustration of the methods implemented in the code three examples are given of the capabilities of SIRIUS for a purely structural calculation and for two situations with fluid-structure interaction