This paper presents the results of a study for the design of a repository capable of storing 400,000 200 litre drums of both low-and medium-level waste in solidified form. It is shown that in a depth of a few hundred meters, tunnels, caverns, and shafts are the favoured geometrical forms for the disposal of this category of waste.
A concept for the overall installations required for the repository including the aboveground operations building, the main shafts and tunnels and the underground plant is described. Consideration is given to the various techniques for the isolation, backfilling and sealing of the cavities together with the handling, safety and radiation protection aspects.
The entire cost of the repository has been estimated to be in the region of 450 - 500 Mio Swiss francs.
In Switzerland, the National cooperative for the Storage of Radioactive Waste (NAGRA) is responsible for the storage and disposal of all types of nuclear wastes. The general strategy for the waste management and the disposal concepts have been presented in the report "Konzept fuer die nukleare Entsorgung in der Schweiz" in 1978. By 1985, NAGRA has to develop proposals for sate and final disposal. The proposed storage scheme consists of 3 types of repositories corresponding to 3 categories of solidified waste according to their origin, activity and toxicity:
High-level waste will be disposed in bore holes or caverns at a depth of 600 m to 2,500 m below ground.
The final storage of low- and medium-level waste (LLW and MLW) will be provided in caverns, tunnels or shafts a few hundred meters below ground.
The waste from maintenance and decommissioning of nuclear plants will be stored in shallow underground caverns or big shafts.
The above-mentioned repository has to be capable of storing 300,000 drums (200 1) of LLW and 100,000 drums of MLW originated from
the operation of power plants
the reprocessing of high-level waste
highly activated components from decommissioning waste
The site of the storage area is geographically undefined but the assumption is made that anhydrite and marl are suitable host rocks for the first model approach.
Safety and radiation protection requirements are those applicable to other existing nuclear plants.
Medium-level waste has to be stored so as to be retrievable in the short term.
The repository consists of the following three main parts:
an above-ground operations building
two main shafts
the underground plant