FEM ANALYSIS AND EXPERIMENTAL VERIFICATION OF THE CONSTOR® STEEL-CONCRETE-SANDWICH CASK UNDER DROP TEST CONDITIONS

The CONSTOR® steel-concrete-steel cask is a Type B(U)F package for transport and storage of spent fuel elements. Aspects of its design development will be presented in a separate paper at the PATRAM 01. The cask body is a steel-concrete-steel sandwich construction. It consists of an outer and an inner steel liner, with the space in between filled with heavy concrete for additional shielding, within a reinforcement frame welded to the inner liner. The closure system consists of a bolted primary lid, a welded intermediate lid and a welded secondary lid. As a final verification of the cask’s integrity in 9m regulatory drops, finite element (hereafter FE) analysis have been carried out using the explicit non-linear code LS-DYNA. The work had two objectives: 1) to verify the FE modelling technique and of the FE model in accurately predicting the drop behaviour of the cask; and 2) to evaluate the integrity of the cask in the 9m regulatory drop scenarios using the validated models. To this end, two FE models of the CONSTOR® were built, one of the ½ scale model cask which had previously been 9m side drop tested, and the other of the full scale cask. The models differ only in dimensional details. All cask components were modelled explicitly, and the concrete was modelled using an anisotropic brittle damage model by Govinjee. Analysis results compared well with test results. This sufficiently demonstrates the capability of FE analysis to simulate the behaviour of casks in impact, and forms a sufficient validation for the model. Integrity of the full scale cask containment was then evaluated under the three drop orientations: side drop, bottom edge drop and lid edge drop. Maximum stresses in all scenarios were lower than the stress limits, hence demonstrating the integrity of the cask in the regulatory 9m drop scenarios.