Abstract:
This paper provides a summary and evaluation of a series of drop tests conducted at Sandia National Laboratories (SNL) and Lawrence Livermore National Laboratory (LLNL) to assess the loading on a spent fuel storage cask. The tests, which included end drops, side drops, and tipover events, were performed using a 1/3-scale model steel billet and various substrate materials, including concrete pads and engineered soil fills. The data collected from these physical tests was used to benchmark a finite element analysis (FEA) approach. A finite element model of the steel billet, concrete pad, and subgrade soil was constructed using the TrueGrid mesh generator to simulate the tests. The billet and cask were represented by a solid cylinder with a perfectly elastic material model for the steel billet and a modified constitutive model for the concrete pad. The constitutive model for the concrete was based on a previous LLNL project and was deemed representative for this study. The simulation results for the billet drops were filtered to remove vibratory components, allowing for a direct comparison with the rigid body deceleration measured in the physical tests. The paper presents a three-step methodology for applying this validated analytical approach to a full-size "generic" storage cask using the DYNA3D finite element code. This method involves using the billet test data to develop a representative material model for the concrete and soil, which is then used in a full-scale simulation of a generic cask to estimate deceleration loads during various low-velocity impacts. This work demonstrates how a benchmarked FEA methodology can be used to confidently predict impact loads on full-scale casks, reducing the need for extensive and costly full-scale physical testing.
