In those cases where the actions which have to be designed for are not well defined, a design according to the "system technology concept" can be considered. This concept has been introduced by Bomhard, particularly for storage for non-tractable wastes . Characteristic for problems associated with the storage of hazardous waste are the often poorly defined chemical and/or biological actions which have to be considered. The chemical composition of the waste is sometimes hard to predict, may vary from place to place in a body of waste and may change with time. For these reasons one has to consider actions, i.e. scenarios, in which degradation of the primary container, e.g. a liner of foil, may occur and result in uncontrolled leakage of any contaminating substance. It is emphasized that, when dealing with poorly defined chemical or biological actions, the efficiency of the barrier can not be quantified properly. For the same reason it is not possible to quantify the increase in safety if a two or more layers of the same type are applied. In those cases the afor mentioned system technology can be the appropriate answer. Characteristic features of the system technology concept are inspectability, controllability, reparability and renewability. An example of the system technology concept from the waste business is shown in Fig. 6. The figure shows a double walled storage system for interim storage of non-tractable waste as proposed by Rudat . The primary container should be accessible from all sides, allowing inspection and control of the container. If due to any unforeseeable reason leakage might occur, the primary container is repairable and, in the ultimate case, renewable.