DROP TEST ANALYSIS OF 1/3 SCALE TK TYPE TRANSPORT AND STORAGE CASK

Safety of spent fuel dry storage system using casks is focused on in these days and this system is expected to be strongly increasing. The design of transport and storage cask for BWR spent fuels, named TK-69 and TK-52 were completed for Japanese utilities. Then, the 9m drop tests using 1/3 scale model for TK-69 were performed. The drop tests were performed with 4 different conditions such as horizontal, vertical, corner and slap-down drop test. The analyses for these conditions are performed with dynamic analysis code LS-DYNA in order to establish suitable analysis method on drop tests for TK type casks. The results of preliminary analysis for the drop tests show good agreement with experimental results concerning overall reaction of the cask such as maximum acceleration, maximum crush deformation of shock absorbing cover (SAC), etc. However, the analysis results does not express similar deformation mode to the experimental results. It was suspected that this difference was caused by the different behavior of wood brocks of the SAC in the analysis. Wood block which is installed in the compartments of SAC is normally combined with separated several parts, and these parts may slide each other during the SAC's deforming. Therefore, for simulating the deformation mode of the experimental drop test more accurately, it is necessary that wood blocks should be modeled as similar separated parts, and friction coefficient of contact surface between these parts should be applied to allow sliding. By applying these assumptions to the analysis, the better agreement concerning deformation mode of SAC can be obtained. Therefore, an existing analysis method is good for the evaluation of overall reaction of 9m drop tests. But if more precise deformation mode of SAC is required, additional consideration mentioned above is necessary. In both analyses, the results have a good agreement with the experimental drop tests of TK type casks concerning such as the maximum acceleration and the maximum crush deformation of SAC.