The geological condition of Konrad

Simplified West–East cross section in the region of the Konrad mine, Shaft 2

The iron ore deposit of the Konrad mine, where radioactive waste is to be disposed of, formed about 150 million years ago in the Jurassic period.

Over time, other strata deposited above the iron-ore containing rocks (mainly marine deposits). Rocks were transported, too. Therefore, not all of the originally deposited strata do exist today. The iron ore deposit is located in the area of the Konrad mine ca. 800 to 1,300 m below the earth's surface. In the area of the Konrad 2 mine it is relatively high and declines to the north.

Natural barrier against groundwater

Nowhere does the iron ore deposit reach the earth's surface and large areas are covered by a 160 to 400-m-thick layer of clayey rocks of the Lower Cretaceous. Overlying this is several-hundred-metre-thick limestone of the Upper Jurassic. The clay stones form an effective natural (geological) barrier to the groundwater and thus to the biosphere.

Exact knowledge of the rock characteristics

The Stratigraphic Location of Iron Ore in the Konrad Mine (Dr W. Diem 1986)

The important rock characteristics, such as the stability of the mine cavities, are well known by the former iron ore mine. Over 90 boreholes drilled for iron ore and oil, with a total length of around 100 kilometres, and geophysical surveys provided a multitude of further information in order to be able to assess whether the Konrad mine is suitable to host a repository. Manifold laboratory examinations on petrography, geochemistry, porosity, permeability and sorption behaviour show, among others, that the Konrad site is suitable to host a repository for radioactive waste with negligible heat generation.