Multi-purpose canister storage of spent nuclear fuel in modular vault system. Technology development

The original Modular Vault Dry Storage (MVDS) technology was developed in the early 1980s leading on from the experience gained with the magnox fuel dry storage facilities at the Wylfa power station in Wales (UK). The Wylfa dry fuel stores were commissioned in 1969 and the MVDS can, therefore, rightly claim to be the only dry fuel storage technology that has an operational and technological background of over thirty years. The MVDS system was originally designed to store individual fuel assemblies within a Storage Canister. This system ensures minimum fuel storage temperatures and provides maximum flexibility for future off-site transportation. Individual fuel assemblies can be removed from their storage locations and placed into a transportation cask for either road or rail off-site shipment. However, this requires each fuel assembly to be re-handled and transferred into the transportation cask. A vault storage system based on the proven MVDS technology using a large Multi-Purpose Canister (MPC), is now being developed to provide a cost-effective interim spent fuel storage system. Integrating the MVDS technology with a MPC and adapting the cooling, shielding and handling systems, allows the new vault storage system to provide high storage efficiency in compact storage buildings suitable for a large spent fuel interim storage facility. It has been possible to reconfigure the vault storage array from individual fuel assembly storage canisters to large diameter canisters, and to re-configure the handling equipment to transfer large canisters. By modifying the design of the MVDS to accept large, multiple fuel assembly, multi-purpose canisters, it has been possible to maintain the technical and operational benefits of the original MVDS design, with the additional benefits of multi-purpose canisters. (author)