Qualification and certification criteria of casks for the intermediate dry storage of spent fuel in the Federal Republic of Germany

As a part of the back end of the nuclear fuel cycle policy of the German Federal Government, the intermediate storage (up to a period of 40 years) of spent fuel elements is seen to be one step on the way to the reprocessing and/or final storage. The alternative to the method which is now practiced, i.e. the intermediate storage in pools (wet storage), this is the intermediate storage in transport casks under dry conditions. With regard to realistic assumptions, the latter will probably be that one to be realized in the FRG in the next years. The ability of already existing spent fuel element cask designs to serve as storage casks led to the fact that in the FRG, four facilities for the intermediate dry storage of spent LWR fuel elements in type B(U) casks are now in the licensing procedure stage: two away-from-reactor (AFR) facilities in Gorleben (Lower Saxony) and Ahaus (North-Rhine Westfalia) with a storage capacity of 1.500 t uranium each; and two at the reactor (AR) facilities at the nuclear power plants of Wuergassen and Stade with a storage capacity of 120 t/240 t uranium. The advantage of the storage in casks-concept is to build a storage facility according to the MAT principle (variable assembly of units) considering the actual need for storage capacity with extension possibilities. Another advantage is the inherent safety and security of the fuel by the cask itself in comparison with the need for additional active systems (e.g. for cooling purposes etc.) for a pool or vault storage facility. The evaluation of such active systems requires more expanded and sophisticated investigations, controlling and analyses. 3 references