Fluid Structure Interaction (FSI) plays an important role in nuclear engineering design, where several tests need to be performed before production. One area where FSI analysis can be used is to determine the sloshing frequencies and hydrodynamic pressure distributions acting on fluid storage tanks. Fuel tanks may undergo different types of loading, including seismic loading, where the behaviour of storage tanks includes material nonlinearities, which are caused by material yielding. Data presented in current tank seismic design codes, such as Eurocode,are based on simplified assumptions for the geometry and material tank properties. FSI simulations are very useful for engineers and designers when defining appropriate shell thickness and material properties of the structure in order to be resistant to seismic loading. The Arbitrary Lagrangian Eulerian (ALE) formulation based on Finite Element analysis presented in the article takes into account the material properties of the structure as well as the complex geometry of the tank.The formulation uses a moving mesh with the mesh velocity defined through the motion of the structure.