Nuclear Power in Switzerland

(Updated March 2019)

  • Switzerland has five nuclear reactors generating up to 40% of its electricity. Two large new units were planned.
  • In June 2011 parliament resolved not to replace any reactors, and hence to phase out nuclear power gradually, and this was confirmed in a 2017 referendum.


Nuclear Power Plants in Switzerland Map

Electricity consumption in Switzerland was growing at about 2% per year from 1980 to 2000, but since then it has declined by about 5% in line with government policy. In 2015 electricity production was 67.7 TWh gross, but this dropped to 62.9 TWh in 2017. In 2017 nuclear power contributed 20.4 TWh (32%), hydro 37.0 TWh (59%), biofuels and waste 2.9 TWh, and other renewables 1.7 TWh (International Energy Agency data). A lot of electricity is imported from France, Austria and Germany (33 TWh in 2015 and 2016) and up to 26 TWh/yr exported to Italy, with total exports and imports largely balanced. To ensure security of supply during winter months, Swiss utilities have long-term contracts with EDF to import 2500 MWe of French nuclear power, at a price premium. In March 2017 the National Council voted 136 to 52 to maintain this arrangement. Per capita consumption is about 7000 kWh/yr. While there are no current plans to build more nuclear plants, $12 billion in hydro projects is reported.


Government policy and industry development

The country's first research reactor – the 10 MW SAPHIR – started up in 1957, having been bought from the USA, and it ran until 1993. A second unit – DIORIT (30 MW) – was designed and constructed indigenously and started up in 1960, running until 1977. In 1960 the Swiss government took over the research centre operating both reactors and in 1988 this became the Paul Scherrer Institute – a flagship research centre.

Construction of an experimental power reactor was commenced in 1962 at Lucens. This was a 30 MWt, 7 MWe heavy-water moderated gas-cooled unit located in an underground cavern. It started up in 1966 but experienced a core melt in 1969 and was written off.

In the 1960s it was evident that Swiss power demand would exceed the potential for supply from hydro sources, so utilities proposed building coal- and oil-fired plants. However, this was strenuously opposed by environmental groups and others on the basis of compromising the hitherto clean power generation, so the government encouraged the utilities to plan for nuclear power.

The country's first commercial units were Beznau 1 – a Westinghouse pressurised water reactor ordered by NOK (Nordostschweizerische Kraftwerke AG) and soon duplicated, and Mühleberg – a General Electric boiling water reactor ordered by BKW (Bernische Kraftwerke AG), located 15 km from Bern.

Following these three units, a consortium of utilities – Kernkraftwerk Gösgen (KKG) – ordered a large PWR from Siemens KWU for Gösgen and the same year another utility consortium (KKL) ordered a similar-sized General Electric BWR for Leibstadt.

A further unit (950 MWe) was proposed for Kaiseraugst near Basel, but this was abandoned in 1988 following anti-nuclear opposition arising from the Chernobyl accident, as was the Graben proposal (1140 MWe). Kaiseraugst investors were compensated CHF 350 million.

Both Beznau and Gösgen produce district heating in addition to power. Beznau makes available 80 MW of heat to industry and homes over a 130 km network serving 11 towns – potentially 2.5 PJ/yr.

All Swiss reactors have had power uprates – the Beznau units from 350 MWe, Mühleberg from 306 MWe (the latest: 17 MWe January 2009, including replacement low pressure turbines), Gösgen from 920 MWe to 1010 MWe to 2014 (with major equipment replacement in 2013), and Leibstadt from 950 MWe progressively to 1220 MWe to 2013.

All Swiss reactors except Mühleberg have unlimited-duration operating licences, as long as they can demonstrate safety to the regulator. Mühleberg must be relicensed every ten years, the latest being in December 2009 on condition that it met nuclear safety requirements. However, in 2012 the Federal Administrative Court ruled that the reactor should close in mid-2013 on safety grounds. It said that the issue of safety was too important to be the sole responsibility of the regulator, the Swiss Federal Nuclear Safety Inspectorate, and that if BKW wanted to operate beyond mid-2013 it would need to make a strong case for that. BKW, along with the Energy Ministry, appealed, and in March 2013 the Supreme Court reversed the ruling. It appears that Gösgen and Liebstadt at least will justify the expenditure required to permit operation to 60 years.

BKW considered its options regarding safety-related upgrades to Mühleberg, and decided in October 2013 to spend some CHF 200 million on safety upgrades and close the reactor in 2019. Prolonging its life to 2022 as planned would involve higher costs in the context of “uncertainty surrounding political and regulatory trends”. In May 2014 citizens of Bern canton effectively approved the 2019 closure date with a 63% vote rejecting an early shutdown proposal. This was the first Swiss public vote on nuclear power since the government 2011 decision to phase it out, and is consistent with a 2013 poll (see below). In January 2015 ENSI approved BKW’s revised maintenance plan for Mühleberg, allowing the company to operate it until 2019. This was confirmed in December.

In 2015 concerns were raised about the manufacturing quality of the reactor pressure vessels of the Beznau reactors, and restart of unit 1 was postponed from July as investigations by ENSI continued. Unit 2 was checked and restarted in December 2015. Axpo said the testing was similar to that used on two Belgian reactors though the metallurgical irregularities were different, and the vessels had been made by Creusot Forge in France. Axpo invested CHF 700 million in unit 1 during its outage, and the same for unit 2, giving them prospective 60-year operating lives. Axpo submitted the safety case for unit 1 to ENSI in November 2016, providing the results of all the tests and analyses it had carried out over the past six months on the vessel in order to produce proof of physical integrity. Axpo said that the results confirmed the safety of the reactor for operation to 2030, but ENSI approval for restart was not expected before March 2017.

Meanwhile the Bern canton government had said that it was prepared to negotiate with BKW and possibly let the Mühleberg reactor run until 2022 since a closure agreed with BKW posed less of a risk to the canton in terms of liability, while also complying with the national energy policy, which calls for the orderly exit from nuclear power. The Bern canton is the majority shareholder in BKW, the remaining shares are held by Groupe E (10%), EOn Energie (7%), BKW FMB Energy Ltd (10%), and 20% held by other parties.

NOK Axpo, operating Beznau and Leibstadt, is part of the Axpo Group owned by the cantons in the northeastern part of the country. Another utility consortium ATEL (now Alpiq) owned 40% of Gosgen and 27.4% of Leibstadt.

In 2009 ATEL merged with EOS to form Alpiq Holding SA, the country's largest power utility. Early in 2009 EdF increased its stake in Alpiq to 25%. One-third of Alpiq's electricity is nuclear.

Operating Swiss Power Reactors

Reactors Operator Type Net MWe First power Expected closure
Beznau 1
NOK Axpo
2019 or 2030
Beznau 2
NOK Axpo
2021 or 2031
Dec 2019
Total (5)
3333 MWe

Energy Policy 1990 to 2011

A ten-year moratorium on new plant construction was supported by 54.6% of the electorate during a national referendum in 1990.

Then in a unique 2003 referendum which would have been binding and written into the constitution, Swiss voters firmly rejected two anti-nuclear proposals which were originally put forward in 1998. "Electricity without Nuclear" was overtly to phase out nuclear power by 2014, while "Moratorium Plus" would have led to a similar outcome by, amongst other things, removing incentives to invest in and upgrade nuclear plants. Two-thirds of voters rejected the first proposal and 58% rejected the second, with practically all cantons refusing both.

In 2006 ATEL was looking for partners to build a further large nuclear power plant using proven technology and probably at an existing nuclear plant site. Also Axpo Holding AG had been studying sites for a new nuclear power plant – possibly Beznau.

The Swiss government announced early in 2007 that the existing five nuclear power reactors should be replaced in due course with new units. The new energy policy included renewables, energy efficiency and gas-fired plants, but had nuclear continuing to carry the main load apart from hydro, which is not amenable to expansion. Without new investment a 20 TWh/yr shortfall was predicted by 2020 – 25% of demand then. This is due to phasing out of an electricity import arrangement from France, closure of the small Beznau and Mühleberg reactors and closure of the 355 MWe Mill Mountain hydro plant, effectively removing 2400 MWe.

In October 2007 the Solothurn canton parliament called for “rapid construction of a nuclear power station in Niederamt” near Gösgen. In 2008, framework approval applications were filed for two projects with large new reactors.* Rationalising these, in December 2010 Axpo, Alpiq and BKW joined forces to form a joint planning company on an equal basis to pursue construction of two identical new nuclear power reactors of up to about 1600 MWe at two of the Niederamt, Beznau or Mühleberg sites. Axpo and one of its subsidiaries would take 59% of the power from the new reactors, Alpiq would take 25.5%, and BKW would have 15.5% – the ratio being according to the three partners' existing shares of Switzerland's nuclear power capacity.

* In 2007 the Resun joint venture was formed by NOK Axpo (57.75%), BKW FMB Energie (31.25%) and Centralschweizerische Kraftwerk (11%) to apply to construct two reactors of up to 1600 MWe each at Beznau and Mühleberg sites. ATEL (now Alpiq) was invited to join the venture, but did not do so at that stage. Then in December 2008 the Axpo Group and BKW FMB Energie filed framework permit applications for new nuclear units at Beznau and Mühleberg, a first step towards the replacement of the three small nuclear reactors there which were due to close 2019-22. Two identical new 1100 to 1700 MWe reactors were envisaged, with hybrid cooling systems to minimize water use. Bids for these were sought by April 2011.

Meanwhile, in June 2008 ATEL (now Alpiq) subsidiary Nuclear Power Plant Niederamt Ltd applied to the Federal Office of Energy for framework approval to build a new nuclear power plant in Niederamt near Gösgen. An advanced 1100 to 1600 MWe reactor was envisaged, with hybrid cooling system which would minimize water use. Estimated cost was €3.7 to 4.5 billion to be shared by partners, with start-up expected after 2020. It sounded out possible partners, including Axpo and BKW FMB Energie. There was strong local support for the project. Alpiq was pursuing this.

In November 2010 the Federal Nuclear Safety Inspectorate (ENSI) drew up definitive appraisals for the Swiss Federal Office of Energy saying that the Niederamt, Beznau and Mühleberg sites were suitable for the purpose of building new reactors. ENSI's findings on the applications were reviewed as part of a public enquiry in mid-2011. A federal decision on granting general authorisations for the plants had been expected but was postponed. The Federal Office of Energy was reported to favour construction of two new reactors, not three. Following developments over 2011-15, in October 2016 the three utilities withdrew their applications for the new power plants.


Training in a control room simulator at Beznau

Energy policy 2011 onwards

However, the seven-member Federal Council decided to ignore a referendum that had supported new nuclear power only one month earlier and declared that the country's nuclear power plants would not be replaced. The National Council on 7 June 2011 voted 101 to 54 to endorse this, so that nuclear energy would be phased out in due course, perhaps 2034 (on the basis of a 50-year operating lifetime for the newest unit). The proposal was also approved by the upper house, the 46-member Council of States, by 3:1, though subject to ongoing review of technology options which might allow new plants.

Following the election in December 2011, the government was to produce a new energy policy without nuclear power and submit that to parliament. In 2014 the Energy Strategy 2050 was considered and the lower house (National Council) energy committee called for the introduction of a system requiring operators to submit plans for improving the safety of reactors after 40 years of service. Subject to approval by the regulator (ENSI), this would enable reactors to continue in operation for a further 10-year period, with no limit to the number of 10-year extensions. If a reactor was judged unfit to continue in operation, the operator would receive no compensation.* A Green Party initiative to limit the life of nuclear power stations to 45 years was rejected. The policy promotes expansion of renewable energy including hydro, with subsidies, and proposes building some gas-fired plants – both CHP and CCGT – with subsidies, and raising electricity tariffs. The National Council largely endorsed the nuclear proposals in December 2014, so that after 40 years the nuclear power plant licence could be renewed for ten years and then possibly another ten years. The ‘no new nuclear plants’ policy was accepted by 115 to 77.

* Axpo responded critically to this ‘long-term operation concept’ proposal: “To begin with it will almost automatically lead to safety shortcomings, compared to the present legal requirements. Secondly it will allow the government to order the shutdown of a reactor, temporarily at least, without any objective shortcomings at the level of the existing legal safety requirements, for purely political reasons. The reactors could only return to production after procedures that will take years. And thirdly the concept would force the operators of nuclear plant, due to the lack of legal and planning certainty, to renounce for economic reasons any further investment in expensive safety-related retrofits and to plan for the premature decommissioning of the reactor in question.”

The Council of States (cantons) voted on the matter in September 2015, and agreed to avoid putting legal limits on the operating lives of reactors. It also rejected the National Council proposal supported by ENSI of requiring operators to submit a long-term operating concept every 10 years once a reactor reaches 40 years of service. The upper house also voted to impose a time limit on the federal renewable energy feed-in tariff subsidy scheme (KEV), and for switching some of the funds supporting wind and solar power to subsidise existing hydropower stations.

Following elections the previous month, in January 2016 the Energy Committee of the National Council voted against imposing any limits on reactor operating life, and against the requirement for 10-year plans and justification as proposed by ENSI, thus lining up with the Council of States. It also voted to reverse the ban on building new reactors, and voted against any lifetime limit for Beznau.

On 21 May 2017 there was a referendum on the government’s Energy Strategy 2050, which was approved by a 58% majority, with voter turnout of 42%. It includes the provision for a gradual withdrawal from nuclear power and a greater reliance on hydro and intermittent renewables. Hydro currently supplies 60% of the country’s electricity, and generation from solar, wind, biomass and geothermal sources is to increase from 2,831 GWh to at least 11,400 GWh by 2035. No construction licences will be issued for new nuclear power reactors and no "basic changes" to existing nuclear power plants will be permitted. The country's five existing reactors will be allowed to remain in operation as long as ENSI considers them safe.

(The National Council – lower house – and the Council of States comprise the Federal Assembly, and the Federal Council of seven members is the executive.)

An annual poll of 2200 people in October 2013 showed that 64% of citizens considered that the country’s five nuclear reactors were essential in meeting the electricity demand – a 3% increase from the 2012 poll figure, but about average from 2001. Three-quarters thought that Swiss nuclear plants were safe, and 68% said that they should remain in operation. While 62% recognised cost advantages in using nuclear energy, only 42% believed that they reduced CO2 emissions. Some 88% said that the country’s energy policy should not jeopardise security of supply, 78% did not want to become more dependent on other countries, and 73% wanted Switzerland to produce all its own electricity. Finally, 78% said they wanted to vote on the country’s energy transition and nuclear phase-out.

In November 2016 a referendum brought by the Green party proposed that nuclear plants be closed after a maximum 45 years in operation. This would have meant three of the five reactors closing in 2017 and the other two in 2024 and 2029. It failed by about 54:46, with voters expressing confidence in both operators and the safety authority, despite a major anti-nuclear campaign. One of the oldest reactors is near Bern, and that canton rejected the accelerated phaseout by 56:44.

Fuel cycle

Uranium is procured on world markets, enrichment is provided by a variety of contractors, and fuel fabrication is similarly diverse.

Radioactive waste management

Radioactive waste is mostly handled by Zwilag, a company owned by the four Swiss nuclear utilities. Its ZZL (zentrales Zwischenlager) commenced operation as a central interim dry cask storage facility for high-level waste (HLW) in 2001 at Würenlingen. This is adjacent to the Paul Scherrer Institute, near NOK's Beznau nuclear power plant, and not far from two others. The Zwilag site also has facilities for incineration (in a high temperature plasma oven), conditioning and storage of low- and intermediate-level radioactive waste (LILW).

There has been no firm national policy regarding reprocessing or direct disposal of used fuel. However, until 2003 utilities were sending it for reprocessing so as to utilise the separated plutonium in mixed oxide (MOX) fuel. Reprocessing has been undertaken by Areva, at La Hague in France and by BNFL at Sellafield in the UK under contract to individual power plant operators. Most used fuel is transported by rail (and ship to UK). Switzerland remains responsible for the separated high-level waste which is returned. About 1000 tonnes of used fuel has been so far sent abroad for reprocessing, but the 2005 Nuclear Energy Act halted this for ten years from mid-2006, and the Energy Strategy 2050 extended the ban indefinitely. Used fuel is now retained at the reactors or sent to Zwilag ZZL for interim above-ground storage, being managed as high-level waste.

Two shipments of separated HLW from the UK in 2015 and 2016 are stored at Zwilag.

The Gösgen plant has limited pool capacity for used fuel storage so will operate an on-site independent fuel storage facility which allows cooling before used fuel is sent to Zwilag ZZL.

Repository plans for HLW

In 1972 a national co-operative for disposal of radioactive waste (NAGRA) was set up, involving power plant operators and the federal government. Since 1983 it has operated an underground research laboratory at Grimsel for HLW disposal.

NAGRA submitted a demonstration of feasibility of disposal report (Entsorgungsnachweis) to the Swiss government in 2002. The report showed that used fuel elements, separated high-level waste and long-lived intermediate-level waste could be safely disposed of in Switzerland. In June 2006, the Federal Council concluded that the legally required demonstration of disposal feasibility for all these had been successfully provided. Meanwhile the 2005 Nuclear Energy Act required the waste management and disposal program to proceed and be reviewed by the federal authorities. Identification of site options for disposal is proceeding under this Act and the Spatial Planning Act with regional participation, and following federal approval the actual site selection in three stages of the Sectoral Plan for Deep Geological Repositories is following.

In 2012 the Swiss Federal Office of Energy (SFOE) undertook a three-month consultation on NAGRA’s 2008 repository plans considering six possible regions. NAGRA pursued investigation of these in 2014 in line with the requirements specified by the Nuclear Safety Inspectorate (ENSI), and two were short-listed in January 2015: in Jura Ost and Zurich Nordost. Each could accommodate both HLW and LILW repositories. Four sites of the original six were in reserve until December 2016 when Nördlich Lägern between the two others was added to the shortlist by ENSI after NAGRA had revived consideration of it. NAGRA had said in 2015: “The siting regions were evaluated and compared in a stepwise process, taking into consideration only scientific and technical criteria; societal and political aspects are not relevant in this respect."

The third phase of the process commissioned by the Federal Council in November 2018 will focus on these three regions, following a detailed review by ENSI of the reports and analyses submitted by NAGRA. NAGRA now expects to submit a general licence application by 2024 to the Swiss Federal Office for Energy. A final decision by the government is expected by 2030, with the possibility of a referendum. NAGRA expects a repository for LILW to be operating by 2050 and one for HLW by 2060.

LILW repository plans

A proposal for a low- and intermediate-level waste repository at Wellenberg was blocked by a cantonal referendum in 1995. A federal working group reviewed the proposal and recommended in 2000 that it proceed, though modified to allow for retrieval. A further cantonal referendum blocked it in 2002. The revised Nuclear Energy Act removes the cantonal veto right, but requires a national referendum.

Low- and intermediate-level waste from the nuclear power plants is processed into a form suitable for disposal either at sites of origin or at ZZL Würenlingen. It is packaged into suitable containers and then stored in facilities at the power plants or at ZZL. Two smaller interim storage sites for this waste have been operating since 1993: the government's BZL associated with the Paul Scherrer Institute at Würenlingen, and Zwibez at Beznau, which also has a storage hall for dry cask storage of spent fuel and high-level waste.

At the end of 2006, the volume of packaged low- and intermediate-level waste was 6830 cubic metres. Added to this are the high-level waste and used fuel stored at the power plants and at Zwilag ZZL. At the end of 2006, there were eight containers with separated high-level waste from reprocessing and 17 containers with used fuel stored at ZZL. (A container is around 6 metres high and 2.5 metres diameter.)


The total cost of radioactive waste management is estimated at CHF 18.6 billion, including a 50-year post-operational monitoring phase. Nuclear plant owners pay into a national waste disposal fund created in 2002. A decommissioning fund was established in 1984 and power plant operators also pay annual contributions to this. The projected requirement is CHF 3.7 billion plus CHF 1.7 billion for post-operational preparation. At the end of 2017 the accumulated capital in both funds was CHF 7.7 billion, with CHF 5.8 billion having already been paid for waste management.

Both programmes are funded under the Nuclear Energy Act by a levy of about CHF 1 cent/kWh on nuclear power production. The government demanded a sharp rise in the contributions to both funds from mid-2014, though both 2011 and 2016 reviews of the funding showed that liabilities would be fully covered.

Decommissioning reactors

BKW intends to proceed with immediate decommissioning of Mühleberg BWR after it is shut down at the end of 2019. The work, costing about CHF 800 million, is expected to be completed in 2031, allowing relinquishment of the site by 2034. A further CHF 1.3 billion is budgeted for waste disposal in about 2040. BKW already has CHF 930 million in its decommissioning fund, and has made provision for more. The fuel will be transferred to the Würenglingen storage facility by 2024, followed by about 4000 tonnes of demolition material which is too contaminated for cleaning and recycle.

In September 2017, BKW acquired German radiation protection services company Dienstleistungen für Nukleartechnik GmbH. The German company has been providing radiation protection services to the Mühleberg plant since 2009.

In March 2015 Alpiq set up a company, Swiss Decommissioning, to offer integrated solutions for post-operation and dismantling of nuclear installations, as well as for radiation protection and decontamination.

The Paul Scherrer Institute submitted an application in April 2013 to the Federal Office of Energy (FOE) for permission to decommission its zero-power Proteus research reactor, which was commissioned in 1968 and shut down in 2011. The Federal Nuclear Safety Inspectorate (ENSI) approved this in 2016. There are two other very small research reactors operating.

Regulation and safety

The main legislation governing nuclear energy is the 1959 Atomic Energy Act. It was updated in 1978 and 2003 (coming into force in 2005). An attempt to limit the operating lives of reactors and ban reprocessing of spent fuel was defeated.

The Swiss Federal Nuclear Safety Inspectorate (ENSI, IFSN in French) is the national regulatory body with responsibility for the nuclear safety and security of Swiss nuclear facilities. It took over from the Swiss Federal Nuclear Safety Inspectorate (HSK) in 2009, but is an independent body rather than being under the Swiss Federal Office of Energy. It monitors and regulates both safety and radiological protection in nuclear installations and waste facilities. HSK was set up under the Federal Energy Office in 1982, and since 2003 there have been legislative moves to make it independent, culminating in a 2007 Act setting up ENSI.

Civil liability for nuclear damage is covered by the 1983 and 2008 Nuclear Energy Liability Acts. Operators have unlimited liability, and they need to maintain insurance coverage. In March 2015 the minimum coverage was raised from CHF 1 billion to €1.2 billion. In 2009 Switzerland ratified the OECD Paris and Brussels conventions.


Switzerland is a party to the Nuclear Non-Proliferation Treaty (NPT) as a non-nuclear weapons state. Its safeguards agreement under the NPT came into force in 1978. It is member of the Nuclear Suppliers' Group but not of Euratom. In 2000 it signed the Additional Protocol in relation to its safeguards agreements with the IAEA.

Notes & references


IAEA 2002, Country Nuclear Power Profiles
ENSI, NAGRA & Zwilag websites


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