CASTOR® HAW28M – DEVELOPMENT AND LICENSING OF A CASK FOR TRANSPORT AND STORAGE OF VITRIFIED HIGH ACTIVE WASTE CONTAINERS

From 1997 to 2006 GNS had returned vitrified high active waste (HAW) from reprocessing in France to Germany by using the GNS cask CASTOR® HAW 20/28 CG. The cask has a capacity of 28 canisters with a maximum total thermal power of 45 kW. 74 casks of this type were loaded at the reprocessing plant in La Hague/ France and have been shipped to the storage facility in Gorleben/ Germany (TBL-G). The remaining HAW canisters at La Hague site exceed the technical limits of the CASTOR® HAW 20/28 CG cask concerning heat capacity and radioactive inventory. Therefore, GNS developed a new cask generation, named CASTOR® HAW28M, which ensures the further return of the HAW to Germany. Hence it is possible to load 28 HAW canisters with a maximum total thermal power of 56 kW. For the CASTOR® HAW28M new materials and new design methodologies were developed and applied. Furthermore, increased heat capacity and sophisticated shielding measures were considered due to reprocessing of fuel with increased enrichment and burn up. The cask design had been subject to a comprehensive drop test programme performed by the Federal Institute for Materials Research and Testing (BAM) following a complex validation of numerical models to realise a transparent proof of the package performance. For normal and hypothetical accident conditions, it was demonstrated that a safe transport and storage of the waste will be ensured also with the new CASTOR® cask design. The CASTOR® HAW28M complies with the IAEA (International Atomic Energy Agency) regulations for Type B package designs containing fissile material and fulfils the acceptance criteria of the TBL-G in terms of radiation protection, heat dissipation and safe confinement under both normal and hypothetical accident conditions. Already in spring of 2003, the application for approval of the Type B package design containing fissile material was submitted to the competent authority. In September 2009 the design approval certificate was issued by the Federal Office for Radiation Protection (BfS). The paper gives an overview on the design characteristics, the cask materials developed and the safety analyses performed.