A study on the free drop impact of a cask using commercial FEA codes

The package used to transport radioactive materials, which is called a cask, must be designed to keep its contents safe under normal and hypothetical accident conditions. The design requirements of the cask are verified by test or finite element analysis (FEA). Comparing evaluation procedures for the safety of a new cask, the cost of FEA is generally much less than that test. Therefore, FEA is mainly used to verify safety of a cask under the considered conditions. However, one commercial FEA code may show different results from another FEA code for the same problem due to the modeler's several assumptions for simplifying actual states into the FE model and due to modeling technique. Materials of the components of a cask display elastic–plastic or elastic–perfectly plastic behavior under the considered conditions in which large deformation, impact and contact mechanism are included. The behavior is simulated with difficulty and may have different results depending on FEA codes. In this paper, finite element analysis is carried out for the 9-m free drop and the puncture condition under the hypothetical accident condition by using LS-DYNA3D and ABAQUS/Explicit. Energy and effective stress on each component are presented and compared between the two FEA codes, where the effective stress designates the maximum von Mises stress on inner and outer shells.