Evaluation of low-velocity impact tests of solid steel billet onto concrete pads, and application to generic ISFSI storage cask for tipover and side drop

Spent Fuel Storage Casks intended for use at Independent Spent Fuel Storage Installations (ISFSIS) typically are evaluated during the application and review process for low-energy impacts representative of possible handling accidents including tipover events. In the past, the analyses involved in these evaluations have assumed that the casks dropped or tipped onto an unyielding surface, a conservative and simplifying assumption. Since 10 CFR Part 72`, the regulation imposed by the Nuclear Regulatory Commission (NRC), does not require this assumption, applicants are currently seeking a more realistic model for the analyses and are using analytical models which predict the effect of a cask dropping onto a reinforced concrete pad, including energy absorbing aspects such as cracking and flexure. In order to develop data suitable for benchmarking these analyses, the NRC has conducted several series of drop-test studies. The tests described in this report were primarily intended to determine the response characteristics of concrete pads during tipover and side impacts of a solid steel billet onto the pads. This series of tests is fourth in a program of tests funded by the NRC; all four series of tests address issues of impact involving spent fuel storage casks. The first series was performed in March 1993 by Sandia National Laboratories (SNL) and involved five end-drops of a billet, nearly identical to the one used in the present series, onto a variety of surfaces from a height of 18 inches. The second series of tests was performed between July and October 1993, and involved four end- drops of a near-full-scale empty Excellox 3A cask onto a full-scale concrete pad and foundation, or onto an essentially unyielding surface, from heights ranging from 18 inches to 60 inches, and was conducted by the British Nuclear Fuels Limited in Winfrith, England. (Two of the drops in the second series were sponsored by Electric Power Research Institute.) The third test series was performed in September 1993 by SNL, and involved eight further end-drop tests of the billet onto concrete pads. These pads were cast on engineered fill resting on undisturbed soil; billets were dropped from heights ranging from 18 inches to 6 feet. The first three series of tests are described in a Sandia report