A methodology for evaluating the response of spent fuel subjected to regulatory transportation accidents

Spent fuel shipping casks in the U.S. are designed to withstand a hypothetical event of a 9-meter drop upon an unyielding target under the regulatory requirements of Part 71 of Title 10 of the Code of Federal Regulations (10 CFR 71). The fuel response under this dynamic impact event constitutes a pivotal role in the source term assessment for spent fuel transport casks. The first step in evaluating the source term is the calculation of the fuel rod dynamic response. This paper illustrates an analysis methodology developed for determining the mechanical response of spent fuel in a transport cask subjected to impact loading. The analysis accounts for the structural interaction between the assemblies and basket, and between assembly hardware and fuel rods. The load transfer paths from the cask to the fuel assemblies depend strongly on the drop orientation. The three possible drop orientations are: (1) side drop; (2) end drop; and (3) corner drop (initial impact and slap down). Structural modeling and simulation of these drop orientations are described and example applications are presented. (author)