Force and Moment Reconstruction for a Nuclear Transportation Cask Using Sum of Weighted Accelerations and Deconvolution Theory*

A 9-m drop test was conducted of a 1/3-scale-model spent fuel cask onto an unyielding target. The structural response of the impact limiters and attachments was evaluated. A mass model of the cask body, with steel-sheathed redwood and balsa impact limiters, was tested in a to-degree slapdown orientation. One end of the cask impacted the target before the other end, as shown in Figure 1, with higher deceleration forces resulting from the second impact. The information desired from this test is the deformation of the two impact limiters on either end of the cask as a function of the applied force. The content in this paper will only discuss a summary of the applied force calculations. Additional details about the force and moment reconstruction methods and analysis results (Bateman et at., 1989) and test and hardware (Yoshimura et at., 1989) are provided elsewhere. Two new force reconstruction techniques were applied to the slapdown test data: the sum of weighted accelerations technique (SWAT) and deconvolution (DECON). The conventional method for determining the resultant force involves post-test digitally filtering an accelerometer measurement to find the rigid-body acceleration for the cask. The rigid-body acceleration is then multiplied by the cask mass to obtain an estimate of the applied force. The frequency content of this force is restricted to the cut-off frequency of the digital filter, typically about one-half of the lowest elastic mode of the cask. The conventional method also restricts the rise time of the force to the rise time of the digital filter. The new force reconstruction techniques demonstrate the potential for a better estimate of forces acting on the cask during the impact than the conventional method.