# Commercial nuclear power plants: type of installation A thematic map of the Atlas of Switzerland, the national atlas published by ETH Zurich. The map is drawn in the browser; this file describes it and lists its variants and links, but not the data values shown on the map. - Map: https://atlasderschweiz.ch/en/theme/commercial-nuclear-power-plants-type-of-installation/ - Short title: NPP: type of installation - Map id: 280 - Categories: Economy and Energy › Primary energy › Nuclear power - Keywords: Current supply, Energy - Published: 2010-11-26 - Last revised: 2026-04-21 - Content language: English - Other languages: [Deutsch](https://atlasderschweiz.ch/de/thema/kommerzielle-kernkraftwerke-anlagenart.md), [Français](https://atlasderschweiz.ch/fr/theme/centrales-nucleaires-commerciales-type-dinstallation.md), [Italiano](https://atlasderschweiz.ch/it/tema/centrali-nucleari-commerciali-tipo-di-impianto.md) ## Description ### General history of nuclear power In 1938, Otto Hahn and his assistant Fritz Strassmann in Berlin provided the first evidence of uranium fission. In 1939, the Danish physicist Niels Bohr brought the latest findings from fission research to the USA. The physicist Enrico Fermi of Columbia University in New York recognised the potential of a controlled fission chain reaction and, together with his team, carried out the first successful reactor experiment, known as Chicago Pile No. 1, in Chicago in 1942. In 1956, the first commercial nuclear reactors for electricity generation in Europe were connected to the grid in France and the United Kingdom. Military applications also developed rapidly: in 1942, the USA launched the so-called Manhattan Project, at times employing up to 150,000 staff and operating under strict secrecy, with the aim of developing weapons of mass destruction using nuclear fission. At the same time, German, Soviet and Japanese nuclear physicists were working on the military use of nuclear energy. On 16 July 1945, the first nuclear weapon test took place with a nuclear explosion under the project name ‘Trinity’. This was followed on 6 and 9 August 1945 by the atomic bombings of Hiroshima and Nagasaki, which claimed hundreds of thousands of lives. ### History of nuclear power in Switzerland The legal foundations of Swiss nuclear energy policy date back to 1946, when Parliament approved the Federal Council’s first resolution on the promotion of nuclear energy. In 1955, over 120 companies founded Reaktor AG in Würenlingen, in the canton of Aargau, a private-sector research centre dedicated to the industrial application of nuclear technology in Switzerland. In 1957, legislation on nuclear energy was enshrined in the Federal Constitution. Two years later, on 23 December 1959, Parliament passed the Atomic Energy Act. In 1960, the Swiss Federal Institute for Reactor Research (EIR) was founded. It was Switzerland’s nuclear research centre and emerged from Reaktor AG. In 1988, it merged with the Swiss Institute of Nuclear Physics (SIN) to form the Paul Scherrer Institute (PSI). The Atomic Energy Act was supplemented by the Federal Decree on the Atomic Energy Act of 1978; this introduced the framework licence and the demonstration of need for the construction of nuclear power stations and transferred responsibility for the safe disposal of radioactive waste to the producers. The Atomic Energy Act and the Federal Decree were replaced on 1 February 2005 by the new Nuclear Energy Act and the Nuclear Energy Ordinance. Under the new Nuclear Energy Act, the granting of a framework licence for new nuclear facilities by the Federal Council and the Federal Assembly is subject to an optional referendum. The nuclear disaster in Fukushima, Japan, in March 2011 led to a rethink. In May 2011, the Federal Council announced that it had decided on a long-term phase-out of nuclear power. On 21 May 2017, the Swiss people approved the Energy Strategy 2050 with 58.2% voting in favour. This resulted in a ban on the construction of new nuclear power stations and a commitment to promoting renewable energies and the more efficient use of energy. #### Accident at the Lucens experimental reactor The experimental reactor in Lucens, in the canton of Vaud, was Switzerland’s first and only nuclear reactor moderated by heavy water and fuelled by natural uranium. It was built in the 1960s in an underground cavern. The reactor went into operation in 1968. It was operated by a consortium of Swiss energy companies and the federal government. On 21 January 1969, a serious accident occurred in the reactor: when the reactor reached an output of 12 MW during commissioning on 21 January 1969, there was insufficient CO2 available to cool fuel assembly 59 due to a blockage caused by corrosion between the water and the magnesium cladding of the fuel rods. Consequently, several of the seven fuel rods in fuel assembly 59 overheated; initially, no one noticed this, as not every fuel assembly was equipped with a temperature sensor in the uranium. At around 600 degrees, the magnesium cladding of the centrally positioned fuel rod finally melted, and shortly afterwards the uranium metal contained within it also melted. A column of molten metal formed (heavy uranium at the bottom, magnesium at the top). The melting process also affected the neighbouring fuel rods. Eventually, the metal began to burn in the CO2 coolant, leading to a massive release of radioactive fission products into the coolant and triggering the reactor’s automatic emergency shutdown. Although this stopped the nuclear chain reaction, it did not stop the fire in fuel element 59. This continued and led to the graphite column enclosing the fuel rods becoming overheated. The graphite column buckled, came into contact with the surrounding pressure tube, overheated it and caused it to burst at 700 to 800 degrees under an internal pressure of 50 bar. The explosion first caused one of the five rupture discs in the moderator tank to rupture. Through this opening, 1,100 kg of heavy water, molten uranium-magnesium and radioactively contaminated cooling gas were hurled into the reactor cavern. About a second later, a chemical reaction between the heavy water (moderator) and the liquid metal led to a second explosion. The pressure surge caused the control rods – which had already retracted by this point – to jam, but did not affect the safety control rods, which were specially protected (by reinforced calandria tubes). The pressure now caused the other four rupture discs of the moderator tank to burst, leading once again to the ejection of radioactive material into the reactor cavern. This process continued over the following minutes until the decompression of the primary circuit into the reactor cavern was complete. Radioactive material was released during the meltdown; however, thanks to the underground design and the rapid response of those in charge, contamination was limited to the cavern and the immediate surroundings. The accident marked a turning point in Swiss nuclear energy policy. It led to greater awareness of the risks of nuclear energy and to stricter safety regulations. The decommissioning of the reactor took approximately five years, concluding in 1974. The radioactive waste generated during dismantling and disassembly was placed in around 230 standard storage containers, conditioned at the Swiss Federal Institute for Reactor Research (EIR) and disposed of by the institute. The complete decommissioning of the entire facility was completed in 1995, 26 years after the accident. The reactor cavern and other sections were filled with concrete and a drainage system was installed. In 2003, the last six large containers remaining on the site were transported to the central interim storage facility ZWILAG in Würenlingen. Today, the Canton of Vaud operates a repository for museums, libraries and archives in parts of the site. ### Switzerland’s large commercial nuclear power plants The first large commercial reactor unit went into operation at the end of 1969 in Beznau on the River Aare (Canton of Aargau). Beznau I is a pressurised water reactor cooled by river water with a net output of 365 MW. It is now the world’s oldest nuclear power plant connected to the grid. The Beznau II reactor, of identical design, went into operation in March 1972. This was followed in November of the same year by the Mühleberg nuclear power plant on the River Aare (Canton of Bern). It is a boiling water reactor with a capacity of 373 MW and river water cooling. The two largest nuclear power stations in Switzerland are Gösgen on the River Aare (a pressurised water reactor with a capacity of 970 MW, in the canton of Solothurn, in operation since November 1979) and Leibstadt on the River Rhine (a boiling water reactor with a capacity of 1,165 MW, in the canton of Aargau, in operation since December 1985). Both reactors use cooling towers. Although Switzerland also pursued military nuclear ambitions in the 1950s and 1960s (during the Cold War and prior to the accident at the Lucens experimental reactor, scenarios were explored regarding how aircraft-based (based on the Mirage III) to fly atomic bombs as far as Moscow), nuclear energy in Switzerland is now used exclusively for peaceful purposes: for electricity generation and for applications in medicine, industry and research. The share of nuclear energy in domestic electricity production stood at 32.9% in 2020 and has fallen gradually as a result of the expansion of renewable energies. Since 2024, the contribution of nuclear power to total electricity production has been below 30%. The four Swiss nuclear power plants (Beznau I, Beznau II, Gösgen and Leibstadt) have a total capacity of around 3 GW; their annual availability in 2020 was 88%. The Mühleberg nuclear power plant has been out of operation since 2019 and is due to be decommissioned by 2034. ### Safety measures When designing, constructing and operating nuclear facilities, operators must implement protective measures in accordance with internationally recognised principles. In the event that dangerous quantities of radioactive substances are released, they must also prepare emergency response measures to limit the extent of damage. The Swiss Federal Nuclear Safety Inspectorate (ENSI) is the federal authority responsible for nuclear safety and radiation protection in the field of nuclear energy. It has a technical and scientific focus. ENSI supervises Swiss nuclear installations with regard to nuclear safety and radiation protection, from the design phase through operation to the decommissioning of the installations and the disposal of radioactive waste. ENSI then establishes security requirements and assessment criteria for protection against unauthorised interference (sabotage). It supervises the security measures taken by operators in technical and organisational areas. ENSI monitors compliance with legal provisions and the conditions imposed by the licensing authority. Furthermore, it takes into account experience and the current state of science and technology worldwide. ENSI reports on its supervisory activities in its annual reports. As an independent body, the Swiss Federal Commission on Nuclear Safety (KNS) advises the Federal Council, the Federal Department of the Environment, Transport, Energy and Communications (DETEC) and ENSI on matters relating to the nuclear safety of nuclear installations. #### Iodine tablets Residents within a 50 km radius of existing active nuclear power plants are supplied with iodine tablets by the operator. They protect the thyroid gland by saturating it with non-radioactive iodine (potassium iodide), so that it can no longer absorb radioactive iodine. The radioactive iodine is then excreted via the kidneys. Radioactive iodine in the thyroid gland would lead to thyroid cancer. The tablets must be taken promptly, i.e. within a few hours before or after radioactive exposure, in the correct dosage. The tablets should only be taken on the instructions of the authorities. Iodine tablets are an effective measure for children, young people, pregnant women and people up to the age of 45 to prevent thyroid cancer. For people over 45, taking iodine tablets is no longer recommended. ### Interim storage and final disposal of nuclear waste When the fuel rods in commercial nuclear power stations reach the end of their service life, the waste – which is still highly radioactive – must be processed, packaged, stored temporarily and finally disposed of. As there will be no suitable final repository until at least 2055, and the highly radioactive waste must in any case be stored on the surface for at least another 30–40 years due to its high heat output, an interim storage facility, known as ZWILAG, was built in Würenlingen, Aargau, not far from the ‘Paul Scherrer Institute’ nuclear research centre and close to the Beznau nuclear power station. ZWILAG was inaugurated in April 2000 and, together with the Federal Interim Storage Facility (Bundes-ZWILAG), which came into operation in 1992, has since been processing and storing all categories of radioactive waste of Swiss origin. This includes operational waste and spent fuel elements from commercial nuclear power stations, waste from the reprocessing of spent fuel elements of Swiss origin at foreign reprocessing plants, as well as radioactive waste from medicine, industry and research. Since 1972, NAGRA (National Cooperative for the Disposal of Radioactive Waste) has been searching for a suitable site for a final repository, a deep geological repository in suitable underground strata. From a geological perspective, Opalinus Clay formations appear to be the most suitable. The three shortlisted sites were Jura East, North of Lägern and North-East Zurich. Ultimately, the ‘North of Lägern’ site was selected. In 2024, NAGRA submitted an application for a framework licence for a deep geological repository at this site in the municipality of Stadel, specifically in the area at the mouth of the Haberstal valley. In 2029, the Federal Council is due to decide on this application for a framework licence and then submit it to Parliament and, around 2031, to the public for a vote, should a referendum be called. ## Sources - Schweizer Armee, Logistikbasis der Armee LBA, Geschäftsstelle Jodtabletten Schweiz (2023): [Verteilung von Jodtabletten: eine vorsorgliche Schutzmassnahme](https://jodtabletten.ch/) - kernenergie.ch (2026): [Die Schweizer Kernkraftwerke](https://www.kernenergie.ch/de/schweizer-kernkraftwerke-_content---1--1068.html) - Wikipedia contributors (2026a): [Liste der Kernkraftwerke in der Schweiz](https://de.wikipedia.org/wiki/Liste_der_Kernkraftwerke_in_der_Schweiz) - ENSI (Eidgenössisches Nuklearsicherheitsinspektorat) (2012): [Serie Lucens: Ausführliche Analyse des Unfalls](https://ensi.admin.ch/de/2012/05/31/serie-lucens-ausfuehrliche-analyse-des-unfalls/) - Wikipedia contributors (2026e): [Kernspaltung](https://de.wikipedia.org/wiki/Kernspaltung) - Wikipedia contributors (2025): [Schweizer Kernwaffenprogramm](https://de.wikipedia.org/wiki/Schweizer_Kernwaffenprogramm) - ENSI (Eidgenössisches Nuklearsicherheitsinspektorat) (2012): [Serie Lucens: Der Rückbau eines Pionierwerks](https://ensi.admin.ch/de/2012/06/14/serie-lucens-der-rueckbau-eines-pionierwerks/) - Wikipedia contributors (2026d): [Kernwaffe](https://de.wikipedia.org/wiki/Kernwaffe) - Bundesamt für Energie BFE (2026): [Elektrizitätsstatistik](https://www.bfe.admin.ch/bfe/de/home/versorgung/statistik-und-geodaten/energiestatistiken/elektrizitaetsstatistik.html) - SFOE (2026b): [Kernenergie](https://www.bfe.admin.ch/bfe/de/home/versorgung/kernenergie.html). Bern: Bundesamt für Energie - SFOE (2026c): [Energiedashboard Schweiz: Stromproduktion](https://energiedashboard.admin.ch/strom/produktion) ## Data sources - ARE (2008): [Energie-Infrastruktur: Kernkraft](http://www.are.admin.ch/themen/index.html?lang=de) - Atlas of Switzerland: [Administrative Einheiten 1:500.000 (Gemeinden, Bezirke, Kantone)](http://www.atlasderschweiz.ch/) - BAG (2022): [Teilrevision Jodtabletten-Verordnung](https://www.fedlex.admin.ch/filestore/fedlex.data.admin.ch/eli/dl/proj/2022/22/cons_1/doc_4/de/pdf-a/fedlex-data-admin-ch-eli-dl-proj-2022-22-cons_1-doc_4-de-pdf-a.pdf). Bundesamt für Gesundheit - ETH Zurich: [Atlas of Switzerland](https://www.atlasderschweiz.ch/) - FSO (2020): [Amtliches Gemeindeverzeichnis der Schweiz](https://www.bfs.admin.ch/bfs/de/home/grundlagen/agvch.assetdetail.11467406.html). Neuchâtel - IAEA, International Atomic Energy Agency (2022): [The Database on Nuclear Power Reactors](https://pris.iaea.org/PRIS/home.aspx) - SFOE (2026b): [Kernenergie](https://www.bfe.admin.ch/bfe/de/home/versorgung/kernenergie.html). Bern: Bundesamt für Energie - swisstopo (2021): [Gemeindegrenzen GG25](https://shop.swisstopo.admin.ch/de/products/landscape/boundaries3D) - swisstopo [J160089] (2010): [Landeskarte 1:500.000](https://shop.swisstopo.admin.ch/de/products/maps/national/lk500) - wikipedia (2023): [Gemeindestandsveränderungen in der Schweiz](https://de.wikipedia.org/wiki/Gemeindestandsver%C3%A4nderungen_in_der_Schweiz) - Wikipedia contributors (2016): [Liste der Kernreaktoren in der Schweiz](https://de.wikipedia.org/wiki/Liste_der_Kernreaktoren_in_der_Schweiz). In: Wikipedia ## Data owners - [Atlas of Switzerland (AoS)](http://www.atlasderschweiz.ch/) - [Swiss Federal Statistical Office (FSO)](https://www.bfs.admin.ch/) - [Swiss World Atlas (SWA)](http://schweizerweltatlas.ch/) - [Federal Office of Public Health (FOPH)](https://www.bag.admin.ch) - [Swiss Federal Office for Spatial Development (ARE)](http://www.are.admin.ch/) - [Wikipedia contributors (Wikipedia)](https://www.wikipedia.org/) - [Swiss Federal Office of Energy (SFOE)](http://www.bfe.admin.ch/) - [International Atomic Energy Agency (IAEA)](https://www.iaea.org/) - [Swiss Federal Office of Topography (swisstopo)](http://www.swisstopo.admin.ch/) ## Citation The terms of use ask to name the Atlas of Switzerland and the data owners, and to keep the source references in exports, screenshots and embeds. Cite the map as: > Atlas of Switzerland (2026): Commercial nuclear power plants: type of installation. ETH Zürich. Map data © AoS, FSO, SWA, FOPH, ARE, Wikipedia, SFOE, IAEA, swisstopo. https://atlasderschweiz.ch/en/theme/commercial-nuclear-power-plants-type-of-installation/ ## Links The map opens at its full extent; a link cannot set the map position. - Map: https://atlasderschweiz.ch/en/theme/commercial-nuclear-power-plants-type-of-installation/ - Short link, stays valid when the title changes: https://atlasderschweiz.ch/en/t/280/ - Side by side with another map: https://atlasderschweiz.ch/en/comparison/?lt=280&rt={id of the other map}&ru={u of the other map, or leave out} Embed in another website (allowed by the terms of use, as long as the source references stay visible): ```html ``` In the embed URL, `dm` sets what is shown: `e` the map with its title bar (default), `p` also the values of an object clicked on the map, `m` only the map with a button that opens it in the atlas. `ig=1` (default) lets the map react to scrolling and dragging only after a click into it, `ig=0` right away. The size can be changed in `style`. ## Related maps - [Annual energy production of nuclear power plants](https://atlasderschweiz.ch/en/theme/annual-energy-production-of-nuclear-power-plants.md) (id 440, former edition, desktop atlas only) - [Nuclear power plants according to type and net capacity](https://atlasderschweiz.ch/en/theme/nuclear-power-plants-according-to-type-and-net-capacity.md) (id 439, former edition, desktop atlas only) ## Maps to compare with - [Population density](https://atlasderschweiz.ch/en/theme/population-density.md) (id 370) - [Earthquakes: heavy earthquakes (magnitude 4.5+)](https://atlasderschweiz.ch/en/theme/earthquakes-heavy-earthquakes-magnitude-4-5.md) (id 436) For the use and citation of maps and data, see the [terms of use](https://atlasderschweiz.ch/en/terms-of-use/).