BENCHMARKING OF ANALYTICAL METHODS AND ANALYSIS SOFTWARE USED FOR TRANSPORTATION PACKAGE DROP ANALYSIS

10 CFR 71 regulations [1] require that the containment boundary of a transport package is able to withstand a 30 ft (9 m) free drop unto a flat, essentially unyielding surface. Impact limiters are designed to limit the deceleration experienced by the cask and its contents during the impact. The design and testing of the impact limiters can be long and tedious. Often, the final design of the impact limiters can only be validated with a full or reduced scale drop test; however the drop test is extremely costly and time consuming. This paper presents a simulation using the LS-DYNA computer code to perform benchmark analyses as an alternative to a drop test. A series of drop tests have been previously performed on a one-third scale mockup of the MP197 Transport Package equipped with impact limiters. The cask was dropped in three different orientations, including a 90º End Drop, 0º Side Drop and a 20º Slap Down. The 90º End Drop was performed with the impact limiters chilled to -20 ºF (-29 ºC) in order to analyze the effect of the low temperature on the impact limiter performance. The impact limiters consist of balsa and redwood, enclosed by stainless steel plates. Balsa and redwood, in the form of wood blocks, provide energy absorption while the stainless steel plates position and confine the wood blocks. The test results include accelerations, maximum crush depths, and impact durations. This paper presents detailed descriptions of how the LS-DYNA code was used to perform the benchmark analysis. This includes: • Description of the finite element models of the cask, impact limiters, and unyielding surface • Material properties • Boundary and initial conditions • Results The results of the LS-DYNA analysis in terms of peak filtered accelerations, maximum crush depths, and impact duration for the three drop cases are presented and compared to the drop test results. It was found that the LS-DYNA analysis results correspond well with the measured impact limiter drop test results. Therefore, the LS-DYNA code simulation can be used to accurately evaluate the impact of a cask with impact limiters.