It is recognised worldwide that, for high-level and long-lived intermediate-level waste, disposal in stable geological formations is the only way to ensure safety over the necessary long time spans. This principle is anchored in the Nuclear Energy Act of 2003 and also applies in Switzerland to low- and intermediate-level waste.
In facilities at the surface, the waste can be directly controlled and monitored and is easily retrievable. However, such facilities require ongoing supervision and maintenance. An absolute prerequisite for this is stable societal conditions over the necessary long timescales. In contrast to geological conditions and the evolution of the engineered safety barriers, social and climatic changes cannot be reliably predicted. Geological repositories are therefore preferable.
Compared to social structures, rock formations can remain stable over millions of years and maintain their favourable properties. In a suitable underground environment, time effectively stands still, while conditions at the surface undergo repeated change (illustrations: W4)