UK Nirex is developing re-usable shielded transport containers (RSTCs) in a range of shielding thicknesses (from 70 mm to 285 mm) to transport immobilised intermediate level radioactive waste (ILW) to a deep repository. The RSTCs are being designed to meet the requirements of the IAEA Transport Regulations for Type B packages, including the requirement to maintain shielding and containment following a drop of 9 m onto an unyielding surface. The RSTCs are essentially monolithic in construction and the heaviest version weighs up to 65 tonnes when loaded with contents. They rely principally on plastic flow of the material of construction to absorb the high energies involved in impact events. Specific features of the designs, such as the solid metal corner shock absorbers and side ribs have been optimised for this purpose. Nirex has investigated the feasibility of manufacturing the RSTCs from ductile cast iron (DCI) or cast steel instead of from forgings, since this would bring advantages of reduced manufacturing time and costs. In this paper the methodology set out in IAEA-TECDOC-717 is applied to the Nirex RSTC, including the application of elastic plastic fracture mechanics methods. (author).