Numerical studies on impact tests of a full-size metal storage cask

The necessity of the interim dry storage of nuclear spent fuel using metal casks has risen year by year. Metal gaskets have been used worldwide to prevent leaks from the metal cask during long-term storage. There are still uncertainties for the impact behaviours of the metal cask without impact limiters under severe impact loads, such as drop or tipping-over events in the interim storage facility. Therefore, it is very important to clarify the dynamic behaviour of the metallic gaskets subjected to sliding and opening movements of the lid structures during impact loads. To demonstrate the structural integrity and leak-tightness of gasketed joints of the metal cask against drop impacts, many impact tests and analysis have been performed based on transport regulations or storage accident scenarios. The inert gas will be released instantaneously under very slightly opening or sliding movements of the lid structures. Until now, there has been less evaluation data concerning the instantaneous leak rates from the lid gasket during impact loading. Therefore, two impact tests with the full-size metal cask (horizontal drop and rotational impact onto concrete floor) have been executed and the relationships between gasket movements and the leak rate of inert gas have been clarified. Moreover, according to the drop analysis using dynamic analysis code LS-DYNA and the comparison with the experimental results, the impact behaviour of the complicated gasketed joints can be simulated accurately and directly.