An investigation on the seismic response of free-standing dry storage cask for spent fuel

For most dry storage facilities for spent fuel worldwide, storage casks are freestanding on concrete pads. Thus, relative motion between the cask and the pad may be induced during earthquakes, leading to stability concerns. In this study, the seismic stability conditions of a free-standing cask were examined quasi-statically. Then, a finite element (FE) cask-pad model considering the frictional contact at the interface was established, and a dynamic analysis was performed to simulate a scaled cask shaking table test, which was conducted at the Central Research Institute of Electric Power Industry in Japan. Furthermore, the influence of friction coefficient of the cask/pad interface on the cask response was investigated using this FE model. Apparent rocking of the cask was induced at a higher friction coefficient, while sliding dominated the cask motion at a lower one. Since the friction coefficient is critical to the seismic stability of a free-standing cask, cyclic loading tests of a scaled pedestal model of a cask system called the High Performance System of the Institute of Nuclear Energy Research (INER-HPS), which will be used in Taiwan, were conducted to investigate the actual friction coefficient at the cask/pad interface as well as the effect of normal stress and sliding rate. Based on the test results, numerical simulations were performed to ensure the seismic stability of this INER-HPS cask under the design base earthquake.