The effect of secondary impact on a spent fuel shipping cask subjected to slant-angle drop tests

According to the IAEA Regulations, any cask for large radioactive sources must be able to withstand the free drop test from a height of 9m onto a rigid target. The regulations require that the cask withstand a drop in an orientation for which maximum damage is expected. Conventionally, either the vertical, the horizontal or the corner drop has been assumed to be the orientation of maximum damage. However, if any arbitrary orientation such as the slant-angle drop is or could be more severe than other orientation, the safety assessment for that case should be done. Recently, it is suggested by many researchers that, depending upon test condition, the secondary impact under slant-angle drop test can result in severe damage compared with other cases. To clarify this point, the authors conducted a series of drop tests with a 1/4 scale model of the spent fuel shipping cask and also carried out dynamic structural analysis by use of DYNA-3D Code. It is concluded ultimately, that the horizontal drop condition is more severe than the slant-angle drop test, from the viewpoint of safety evaluation for container-body itself