Aging Management in the Design and Operation of Dual-Purpose Casks

CASTOR® casks are dual-purpose casks for high active nuclear waste that have to fulfill the requirements from both transport (acc. to IAEA regulations) and storage (acc. to national regulations). The first CASTOR® cask was loaded with spent nuclear fuel in 1983 in Switzerland. Since the 1990s, casks of the CASTOR® type with high active waste from reprocessing plants have been stored in Germany. According to the storage licenses in Germany, the CASTOR® casks are licensed for a storage period of 40 years. By now more than 1000 casks have been loaded and stored worldwide. GNS is both supplier of the casks and operator of the two centralized storage facilities. In combination with the continued longtime use of CASTOR® casks GNS has unique operational experience covering the entire lifetime cycle: from design, licensing, via manufacturing, loading, and transport up to storage. The main approach for long-term storage is to prevent or to minimize the aging effects by design or maintenance measures. In general durable materials are used which are not subject to corrosion or the degradation mechanism by irradiation. The cask body consists of ductile cast iron and its surfaces which may be in contact with corrosive atmospheres are protected by a multilayer paint system. Furthermore, critical material combinations which may lead to degradations should be excluded. For components which are affected by aging, the change of its properties is considered in the design.