A preliminary study is presented for final storage for low- and medium-level waste in crystalline rock at shallow depth. The study deals with a suitable transport- and handling system for waste packages, design of three different types of rock cavities and varying manmade barriers, the activity dispersion through the man-made barriers, dilution conditions in the groundwater and doses to individual and mankind. The study shows that large rock vaults will give the lowest costs and the doses to individual and mankind is far below the natural radiation.

BACKGROUND

Over the past few years, considerable efforts have been devoted to solving the question of how the high-level waste is to be finally disposed of with adequate safety. The problem of disposal (final storage) of the low-level waste has only been dealt with cursorily. It is true that similar problems exist for both types of waste, but there are nonetheless a number of important differences. For many reasons, which we cannot go into here, it is best if the high-level waste is not placed in terminal storage for another 30–40 years. In the interim, the waste will be stored in CLAB (central temporary storage facility for spent fuel), which is to be built in Oskarshamn. As far as the low-level waste is concerned, existing storage facilities will have to be expanded within the near future.

The temporary storage facilities located at the nuclear power stations are normally designed to accommodate the waste from 5 or, at the most 10 years of production. Since additional storage facilities have to be built anyway, it would be clearly advantageous if they could be designed to function as final storage facilities in the future as well. This would also permit valuable experience to be gained for the storage of the more complicated high-level waste later on. The amount of low-level waste is many times greater than the amount of high-level waste.

For this reason, even though the demands on the storage premises are considerably lower, great economic gains can be made by an earlier final storage of the low-level waste. The National Council for Radioactive Waste (PRAV) has therefore been studying the transportation and final storage of the low-level waste for 2 1/2 years now. The risks of dispersal 1n nature have also been studied, and the ~of adverse impact on biological life have been assessed. The goal has been to have a final repository finished by the time the temporary storage facilities at the nuclear power stations are filled (1986–88), but this would now appear to be impossible. It will probably be necessary to expand the temporary storage facilities to accommodate an additional 2 years of production at most nuclear power stations.

The geological conditions necessary for an underground final repository in Sweden exist only in crystalline rock. There are small formations of sediment in some parts of the country, but these formations are generally relatively near the surface and situated in areas of high population density, and are therefore judged to be less suitable for the location of a final repository for the waste.

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