For transportation and interim storage, Germany developed and licensed the CASTOR® cask system. This system includes a number of different variants based on the intended contents. However, in general all CASTOR® containers consist of a double-shell design sealed with two separate end-cap sealing systems. The cask body consists of a large cylindrical 30-40 cm thick — walled casing made of ductile cast iron steel. The interior of the CASTOR® container is nickel plated. For neutron moderation, axial boreholes are distributed uniformly in the cask wall to accommodate moderator rods. The

bottoms of the containers are sufficiently thick to provide gamma and neutron shielding. The lid system consists of a double-barrier sealing system upon which a third protective cover is placed during storage. During trans­portation, both the lid and the bottom ends are protected by large steel — plate shock absorbers. The exterior design of most of the CASTOR® containers incorporates cooling fins designed to radiate access thermal energy from SNF or HLW that are still generating heat. The casks are loaded under water. Today the most widely used CASTOR® containers are the types CASTOR® V/19 (for the contents from 19 spent fuel assemblies used in pressurized water reactors) and CASTOR® V/52 (for the contents from 52 spent fuel assemblies used in boiling water reactors). These contain­ers are approximately 6 m long with a diameter of approximately 2.5 m and weigh approximately 125 tonnes when fully loaded (GNS, 2011b ; BAM, 2010). Feasibility studies are currently under way regarding the potential use of the CASTOR® cask for geologic disposal. A typical CASTOR® is shown in Fig. 14.2.