Evaluation of the use of homogenized fuel assemblies in the thermal analysis of spent fuel storage casks

Thermal analysis of spent fuel storage casks has generally been based on the assumption that heat released by the fuel assemblies is transported to the cask cavity only by conduction through the walls of the basket. This conservative assumption was adopted to compensate for uncertainties in modeling heat transfer in the cavity of a spent fuel cask. During recent years, some applications have submitted safety analysis reports for spent fuel storage casks that challenge this assumption. They offer two methods which include the fuel assemblies, as well as the walls of the basket, as part of the path for heat transfer to the cask cavity. A third method, the consideration of a fuel assembly as a homogeneous log, is explored in a study described in this report