The National Cooperative for the Disposal of Nuclear Waste (Nagra) had to demonstrate the feasibility of the disposal of low- and intermediate-level as well as high-level waste. The Federal Council approved the demonstration of feasibility for all waste categories, thus paving the way for radioactive waste to be stored in deep geological repositories over the long term.
The demonstration of feasibility was first called for in the federal resolution of 6 October 1978 concerning the Federal Nuclear Energy Act. In 1988, the Federal Council approved the demonstration of feasibility for low- and intermediate-level waste, after Nagra had supplied the required evidence based on a repository in marl host rock beneath the Oberbauenstock (canton of Uri).
Then, at the end of 2002, Nagra submitted an application for a demonstration of feasibility for the disposal of high-level radioactive waste, which was based on the opalinus clay formation beneath Zürich Weinland (now Zürich Nordost). The Federal Council accepted this demonstration of feasibility in 2006.