Year
2003
Abstract
The responses of a spent fuel rail cask and a spent fuel truck cask to extra regulatory impacts (representing extreme accident conditions) were examined by Sandia National Laboratories (SNL) to aid the Nuclear Regulatory Commission (NRC) in the development of the Package Performance Study (PPS) test protocols [1]. The purpose of this study is to examine casks under conditions that greatly exceed the severity of the regulatory impact tests. In the regulatory drop test, casks are dropped from a height of 30 ft onto a rigid surface and reach an impact velocity of 30 mph. The kinetic energy of the falling cask is absorbed primarily by the impact limiter assemblies, which mitigate the forces that are applied to the cask body. For the development of the PPS Protocols, the impact velocity was increased by over a factor of two, quadrupling the kinetic energy. This exceeded the energy absorbing capabilities of the impact limiters and resulted in much larger forces being applied to the cask body. Scoping finite element analyses of the extra regulatory impacts were conducted for one representative rail and one representative truck package assembly. The analyses were conducted using the Sandia developed, non-linear transient dynamic finite element code PRONTO3D [2]. PRONTO3D is a shock-wave propagation code developed specifically for impact analyses. It uses an explicit time integration algorithm for solving the equations of motion. The rail cask was analyzed for a CG-over-corner impact onto a rigid surface at velocities between 60 and 75 mph. The truck cask was analyzed for a side orientated “back-breaker” impact onto a rigid cylindrical surface. The back-breaker orientation actually bypasses the impact limiters, which results in the impact loads being applied directly to the cask body. These analyses are also performed for velocities between 60 and 75 mph. The structural response of each cask to these extreme loading conditions is presented.