Nuclear energy: Reliable base load energy

How it works

A nuclear power plant uses the energy of nuclear fission to produce electricity. It is a thermal power plant  like coal-fired or gas-fired power plants. The difference is that nuclear power plants do not produce air pollutants or greenhouse gases during heat production.

In a nuclear power plant, uranium atoms are fissioned in the reactor under controlled conditions. The energy released is used to heat water under high pressure, just like in a pressure cooker. This produces hot steam. This steam drives a steam turbine which is connected to a generator. The generator then produces electricity, which is supplied to consumers via the power grid.

Nuclear or atomic power?

In 1899, the physicist Hans Geitel coined the term atomic energy for phenomena occurring in connection with radioactive decay processes. Subsequently, the synonyms atomic nuclear energy, atomic power, nuclear power and nuclear energy came into use. In recent decades, the use of these terms has increasingly been accompanied by politically and ideologically motivated implications. A conference with high-ranking scientists held in Geneva in the mid-1950s was entitled International Conference on the Peaceful Uses of Atomic Energy and became known in the German media as the Atomic Conference. The International Atomic Energy Agency (IAEA) was founded in 1957. The lobby association in Germany was founded in 1959 as the German Atomic Forum. In the following decades, however, the proponents of the technology distanced themselves from the prefix atom and used the prefix nuclear exclusively in Germany. Parallel to this, the transition from atomic to nuclear also took place in Anglo-Saxon regions, the reason being the unwanted association with the negatively connotated term atomic bomb. Critics, on the other hand, retained the prefix atom. They continue to refer to atomic energy and atomic power plants (nukes).

Our assets

Axpo maintains nearly 40 Prozent of installed production capacities in Swiss nuclear power plants. Axpo's power plant portfolio includes its own Beznau nuclear power plant, including Beznau 1 and Beznau 2, investments in the Leibstadt and Gösgen partner nuclear power plants and procurement rights to French nuclear power plants. Like hydroelectric power plants, nuclear power plants supply important base load energy that is constantly available and CO2-free in production.

Beznau nuclear power plant (KKB)

consists of two largely identical plants, each with a light water reactor and a capacity of 365 megawatts each. The two plants are designed for 8000 full load hours or around 355 operating days per year. Together they generate around 6000 gigawatt hours of electricity per year. This corresponds to about twice the electricity consumption of the city of Zurich. Beznau 1 and Beznau 2 went into operation in 1969 and 1971, respectively. Beznau 1 is Switzerland's first nuclear power plant. However, safety has not been compromised: Continuous investments in safety and ongoing modernisation ensure that both plants are up to date. The Beznau nuclear power plant is wholly owned by Axpo. 

Leibstadt Nuclear Power Plant (KKL) 

The KKL has an output of 1275 MW and is located on a 24-hectare site in the town of Leibstadt, Canton of Aargau, on the Rhine River. It went into operation at the end of 1984, making it the newest and most powerful of the five nuclear power plants in Switzerland. In full operation,  the KKL generates around 9600 gigawatt hours of electricity per year with a boiling water reactor. This volume is sufficient to supply 2 million Swiss households with electricity and corresponds to around 15% of Swiss electricity production. The Leibstadt AG nuclear power plant is managed as a partner plant. Each shareholder of a partner plant bears a proportionate share of the operating costs and receives the energy to which it is entitled. The shareholders of  KKL AG are: AEW Energie AG with 5.4 %, Alpiq AG with 27.4 %, Axpo Power AG with 22.8 %, Axpo Solutions AG with 16.3 %, BKW Energie AG with 14.5 % and Centralschweizersiche Kraftwerke AG with 13.6 %. Axpo is the company's managing director.

Learn more about the Leibstadt nuclear power plant here.

Nuclear power plant Gösgen (KKG)

Anyone travelling by train in Switzerland is familiar the nuclear power station located between Olten and Aarau. The first Swiss nuclear power plant of the 1000-megawatt class went into commercial operation in November 1979. Since then, the KKG has carried out several modernisation projects to further increase safety and has a capacity of 1060 MW. The KKG generates around 8000 gigawatt hours of electricity per year. Five partners hold interests in Gösgen-Däniken AG, the nuclear power plant operator: Alpiq AG (40%), Axpo Power AG (25%), City of Zurich (15%), Centralschweizerische Kraftwerke AG (CKW, 12.5%) and Energie Wasser Bern (ewb, 7.5%). Alpiq is responsible for the management of the company.

Learn more about the Gösgen nuclear power plant here


Axpo has set itself the goal of ensuring that the nuclear facilities it manages are among the best and safest in international comparison. That is our ambition. Axpo is committed to complying with the standards for the safety of nuclear facilities laid down at international level by the IAEA (International Atomic Energy Agency) Safety Convention  and ratified by Switzerland. National and international authorities regularly inspect our facilities.

Periodic safety reviews are of great importance in this context. They serve as a basis for measures to maintain and improve the safe operation of the plants. In addition, safety is regularly analysed and assessed by the WANO (World Association of Nuclear Operators). WANO is a worldwide association of nuclear power plant operators for the mutual exchange of knowledge and experience.

The safety standards of Swiss nuclear power plants are among the highest in the world. The current practice of continuous upgrading has led to a high safety culture, which is also reflected in the low malfunction susceptibility of Swiss nuclear power plants and their high availability by international standards. In the course of European stress tests, which attested a very high level of safety for the Swiss plants, the Swiss Nuclear Safety Inspectorate ENSI repeatedly confirmed their safety.

Strict supervision

In addition to the operators, the Federal Nuclear Safety Inspectorate ENSI is also responsible for the safety of the Swiss nuclear facilities. All nuclear installations are fall under ENSI's supervision: The nuclear power plants, the Zwilag interim storage facility for radioactive waste, as well as the nuclear research facilities of the Paul Scherrer Institute in Villigen, EPF Lausanne and the University of Basel. As an independent institution under public law, ENSI regulates every step in and around nuclear energy, from project planning and operation to decommissioning and disposal of radioactive waste. This also includes protecting personnel and the public from radiation and the nuclear facilities from sabotage and terrorism.

You can find out more about earthquake safety, radiation protection or the liability of nuclear power plants on the website of the industry organisation swissnuclear. 

Service life

According to Swiss nuclear energy legislation, a nuclear power plant in Switzerland can remain in operation as long as it meets the legal safety requirements. There are no plans for a run-time limit of nuclear power plants.

The plant operation depends both on technical conditions and on regulatory and economic factors. Axpo plans to continue operating its power plants as long as they are safe and economical.

There is no justifiable reason to limit the run-time of tried and tested nuclear power plants, as nuclear power opponents are demanding. The supervisory authority ENSI also considers this to be unnecessary. In addition, nuclear energy plays an important role in the Energy Strategy 2050. As a bridge technology, it contributes to Switzerland's security of supply and gives us the necessary time to implement the desired transformation of Switzerland's electricity supply system towards more renewable energies. 

Decommissioning and disposal

Nuclear power plant operators are also responsible for decommissioning and the disposal of radioactive waste. Thus, the total costs for operation, post-operation, dismantling and disposal of radioactive waste are included in the electricity price ex-works according to the polluter-pays principle. Over an operating period of 50 years, these costs amount to around one centime per kilowatt hour. 

The disposal costs incurred during the operation of the power plant are paid by the operators on an ongoing basis. These costs include interim storage, transport, containers for transport and interim storage, and the preparation of radioactive waste for subsequent storage in deep geological repositories. In addition, the operators pay into two funds supervised by the Swiss government throughout the operating period. Together with the return on fund assets, these contributions cover the total costs for decommissioning and waste disposal. This ensures that the necessary funds are available for the decommissioning and disposal costs incurred after decommissioning. 

Cost studies

Expected future costs are estimated every five years under the supervision of the Swiss government in cost studies based on the current state-of-the-art in science and technology. These cost studies form the basis for the determination of the fund contributions by the nuclear power plant operators and for the necessary provisions to be made by the operators. The cost studies are reviewed by the federal supervisory authority and independent experts. The aim is to ensure that the consistent application of the precautionary principle and the polluter-pays principle does not result in uncovered costs for the federal government or future generations.


Even during operation, a nuclear power plant generates various types of waste. The highly radioactive spent fuel elements account for only a small part of this. After removal from the reactor, they are first stored in decay basins in the nuclear power plant. After five to ten years they are transported to the plant's own interim storage facility or the Zwilag central interim storage facility in Würenlingen. In terms of volume, around nine times more low-level and medium-level radioactive waste is generated in nuclear power plant operation than high-level radioactive waste. 


The Mühleberg nuclear power plant, which belongs to the BKW Group, is the first Swiss nuclear power plant to be decommissioned as of 20 December 2019.

The decommissioning is a complex and challenging project and, like the operation of the power plants, it is monitored at every step by the supervisory authority ENSI.

How the Beznau nuclear power plant deals with the topic of decommissioning can be found in our Beznau nuclear power plant dossier.

You can read more about the dismantling of Mühleberg here on the BKW website.

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