Nuclear energy is Switzerland's second major electricity source, with five stations accounting of about 38% of the country's output in 2005. This compares with 78% in France and 20% in Britain in 2004 according figures issued by the Statistical Office of the European Union, and 18.6 % in the US in 2003, according to figures from the International Atomic Energy Agency.

In 2007 the Swiss government announced a new energy policy which included the possible construction of further nuclear power plants.

Although nuclear stations produce no CO2 emissions, they present a serious problem of long-term waste disposal and will continue to do so even when they are no longer in use. High-level nuclear waste remains dangerous for around 250,000 years.

Disposal of nuclear waste

High-level radioactive waste from Swiss nuclear power stations is currently stored in an interim facility known as ZWILAG, built on the premises of the Paul Scherrer Institute. In about 40 years, when it has cooled down, it will be transferred to a site whose geology makes it safe for permanent storage. The location of this permanent site has not yet been determined.

Project studies for the permanent site are looking at the opalinus clay of the Weinland of canton Zurich as a potential host rock. However, the Federal Council has asked for other options not to be ruled out.

Research into various aspects of radioactive waste disposal is conducted in the Grimsel research laboratory, a tunnel system cut in granite rock 450 meters under the surface of the Bernese Oberland, opened in 1984. Swiss and foreign scientists use the facility to investigate such phenomena as water movement and the transport of radioactive materials in rock, and to test equipment.