Technical design of on-site interim stores

The direct disposal of spent fuel elements provided for in the German Atomic Energy Act must be preceded by a period of interim storage to reduce the activity inventory. As a consequence of limited capacities of the in-plant spent fuel storage pools, additional interim storage capacity needs to be created. In Germany, dry interim storage of fuel elements in suitable casks is the preferred technique. An on-site interim storage concept meeting these requirements has been developed by STEAG and is described in this article. On-site interim stores must meet a number of criteria both with respect to their conceptual design aspects and with regard to the protection they must offer against accidents and external impacts. In addition, site-specific factors impose other boundary conditions affecting planning. Important factors, such as thermal output, dose rate, and positioning pattern, are a function of the CASTOR(C) V/19 and CASTOR(C) V/52 type casks available for storage. On the basis of these data it is possible, by employing the most recent computing tools, to design interim stores to the state of the art with respect to external shielding of the storage building, heat removal from the building, and cask temperatures. The results demonstrate that the most important design objective, i.e., meeting the goals of protection, is being attained.