ANALYSIS FOR THE INFLUENCE OF THE FREE-STANDING DRY STORAGE CASK SEISMIC RESPONSE SUBJECT TO RETAINING BARS

摘要

The dry storage facility is critical to nuclear power because the management and storage of the high radioactive waste has always been an important issue. In Taiwan, the available space of spent fuel pools is going to be exhausted in a few years. Therefore, the installation of dry storage facilities for interim storage for spent fuel is necessary. However, according to the previous studies and the event report of North Anna power plant, relative motion of a free-standing dry storage cask to the pad on which it is located may be induced during a huge earthquake. In this study, the seismic behavior of the free-standing dry storage cask constrained by four retaining bars was investigated. The retaining bars are steel bars partially embedded in the concrete pad around the cask to constrain the movement of cask during an earthquake. The ANSYS/LS-DYNA code was adopted to analyze the seismic response of the constrained dry storage cask. A 3D finite element model consisting of a cask, four retaining bars and a concrete pad was established with the simulation of the nonlinear frictional contact at their interface. Analyses for the seismic responses of the cask at various values of the friction coefficient were performed. The results show that sliding and rocking of the free-standing cask will be induced at the onset of its relative motion to the pad at different friction coefficients during a strong earthquake. However, the movement of the cask is confined by the retaining bars and thus the collision between casks can be avoided.