[en] The purpose of this study was to identify realistic designs for large rail casks which have been optimized for the shipment of 2-, 3-, 5-, 7-, and 10-year-old PWR fuel assemblies. To operate and evaluate the various designs, extensive use was made of the SCOPE program which was developed at Oak Ridge National Laboratory as an inexpensive scoping code for Shipping Cask Optimization and Parametric Evaluation using tabulated shielding-thicknesses specified by the user, and a fixed set of optimal packing arrangements, the code will design a cask to carry a single fuel assembly, and then increment the number of assemblies until one of the design limits, such as the overall weight, is exceeded. For each design, the code will calculate the steady-state temperature distribution throughout the cask and perform a complete 1-D space/time transient thermal analysis following a postulated half-hour fire. By using the SCOPE program, a wide range of conceptual designs were evaluated at minimal cost. About 100 cases of potential interest are presented