Year
2007
File Attachment
182.pdf231.57 KB
Abstract
Because of the evolution of the burn-up of used fuel to be reprocessed, the high activity vitrified residues would not be transported in the existing cask designs. Therefore, TN International has decided in the late nineties to develop a brand new design of casks with optimized capacity able to store and transport the most active and hottest canisters: the TN™81 casks currently in use in Switzerland and the TN™85 cask which shall permit in the near future in Germany the storage and the transport of the most active vitrified residues defining a thermal power of 56 kW (kiloWatts). The challenges for the TN™81 & TN™85 cask designs were that the geometry entry data were very restrictive and were combined with a fairly wide range set by the AREVA NC Specification relative to vitrified residue canister. The TN 81 & the TN 85 casks have been designed to fully anticipate shipment constraints of the present vitrified residue conditioning. It also used the feedback of current shipments and the operational constraints and experience of receiving and shipping facilities. The casks had to fit as much as possible in the existing procedures for the already existing flaks such as the TN 28 cask and TS 28 V cask, all along the logistics chain of loading, unloading, transport and maintenance. In addition, years of feedback and experience in design and operations - together with ever improved materials - have allowed finding further optimization of this type of cask design. In order to increase the loading capacity in terms of radioactive source terms and heat load by 40%, the cask design relies on innovative solutions and benchmarks from the current shipping campaigns. Currently, TN 81 and TN 85 are the only licensed casks that can transport and store 28 canisters with a total decay heat of 56 kW. It contributes to optimise the number of required transports to bring back high level waste residues to their producers. Three units have already been loaded and transported to ZWILAG (Zwischenlager Würenlingen AG) in Switzerland where they are stored for 40 years. Based on the same design but integrating the German Authorities and German users specificities, the TN 85 cask is dedicated to the transport and storage of vitrified residues to Germany. It is presently at the final licensing stage. The transport cask approval expertise has now been granted, and the storage expertise is in the final steps. The first transport with TN 85 cask is scheduled up to now in 2008 and the commissioning operations are under preparation. These two casks are key elements for the whole reprocessing system of AREVA as they enable the transportation and the storage of the vitrified residues.