PROTECTING AGAINST CORNER IMPACTS: SENSITIVITIES DISCOVERED DURING A RAIL CASK IMPACT LIMITER DESIGN

Type B packages for the transportation of radioactive materials must remain “essentially leak tight” under severe regulatory accident conditions, defined in the U.S. Nuclear Regulatory Commission’s 10 CFR 71.73 and the International Atomic Energy Agency’s TS-R-1. The 9-m free drop test requirement onto an unyielding surface is performed in an orientation “for which maximum damage is expected”. Analytical techniques are used to evaluate various possible impact orientations before testing, and historically these maximal damage orientations have been side, slap-down, end, and center-of-gravity over corner (CGOC). Other orientations are rarely considered. Sandia National Laboratories (SNL) was asked by Equipos Nucleares, S.A. (ENSA) to design, analyze, and test an impact limiter system for a newly designed rail cask. During the conceptual design process, SNL performed due diligence and evaluated a wide spectrum of possible impact orientations, in order to assure that peak cask body acceleration design goals were not exceeded. But design of the impact limiter, including not only crush strength of constituent materials (which can be orientation and temperature dependent), but also the shape of the impact limiter, greatly affects peak acceleration response during 9-m drops in various orientations.