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Around 1.8 billion years ago, natural nuclear reactors were formed in a uranium ore deposit in Oklo (Gabon, Africa). Chain reactions occurred, producing several tonnes of highly active fission products; these fission products are still retained in the rock today. Nature thus created the first «high-level waste repository» at Oklo. (Image: Nagra)
Ammonite found at a depth of 652 metres in the Opalinus Clay of the Benken borehole. The remains of this creature that once lived in the ocean have been preserved and protected by the clay from external influences for more than 180 million years. (Image: Comet Photoshopping)
Preserved wood at Dunarobba
The isolation capacity of clay is shown clearly by this example of a tree-trunk that was preserved for two million years – in the form of wood – in a clay-pit at Dunarobba in Italy. (Image: Chapman)
Roman helmet from Augst
High-level waste and spent fuel are packaged in steel containers for disposal in a deep repository. Archaeological finds such as this Roman helmet from Augst (Canton Basel) show that iron corrodes very slowly in clay material. (Image: Nagra)
Maqarin research project
In Maqarin (Jordan), the influence of natural highly alkaline waters on fractured limestone was investigated as an analogue for the effects of cement porewaters from a repository on the surrounding host rock. (Image: Nagra)