Swiss federal authorities

Nuclear Facilities

Switzerland has the following nuclear power plants: Beznau (units 1 and 2), Gösgen and Leibstadt. Also in operation is a research reactor at the Federal Institute of Technology in Lausanne (EPFL). The Central Interim Storage Facility for radioactive waste (Zwilag) and the Federal Government’s Interim Storage Facility in Würenlingen are also monitored by ENSI.

The no longer operational Mühleberg Nuclear Power Plant is being decommissioned. Three research reactors at the Paul Scherrer Institute PSI in Würenlingen have nearly been fully dismantled.

  • NPP Beznau
    Beznau NPP comprises two largely identical two-loop pressurised water reactor units, which began commercial operation in 1969 and 1972 respectively. The net electrical output per unit is 365 MW.
  • NPP Gösgen
    Gösgen NPP is a three-loop pressurised water reactor system. It began commercial operation in 1979. The net electrical output is 1010 MW.
  • NPP Leibstadt
    Leibstadt NPP is a boiling water reactor that began commercial operation in 1984. The net electrical output is 1233 MW.
  • Former Mühleberg Nuclear Power Plant (permanent shutdown)
    Mühleberg NPP, which began commercial operation in 1972 and shut down in 2019, was a boiling water reactor with a net electrical output of 373 MW. Mühleberg NPP ceased power operations on 20 December 2019. In 2020, all fuel elements were transferred from the reactor pressure vessel to the fuel pond and the necessary measures implemented to establish safe technical post-operation. In 2022 and 2023, during decommissioning phase 1, Mühleberg NPP transported all its fuel elements to the Central Interim Storage Facility of Zwilag in Würenlingen, completing the first decommissioning phase in 2023. Since then, Mühleberg NPP has been in decommissioning phase 2.

Decommissioning of the following plants has been completed:

  • Lucens experimental nuclear power plant
  • Basel University Research Reactor
    Up until its final shutdown in 2015, the research reactor of Basel University was used to teach students and for neutron activation analysis. After the Federal Department of the Environment, Transport, Energy and Communications (DETEC) had ordered the decommissioning of the research reactor on 13 February 2019, ENSI approved the dismantling of the plant. Dismantling was completed in 2019. With the removal of the plant from federal government oversight, the first decommissioning project in Switzerland under the current nuclear energy legislation was completed.

Background Articles

  • Background articles, Posts

    Unannounced inspections

    «I’m a site inspector for ENSI, responsible for the Beznau NPP. Every week I pay a control visit to the nuclear power plant without prior announcement. I’m interested in everything, including ladders that have fallen over and that you can trip over. Thanks to their training and experience, inspectors know what to look for. We…

  • Background articles, Posts

    A focus on upgrading

    «Nuclear power plants are periodically upgraded with modern technology, such as here in Beznau. Together with my section I check, in a multi-stage approval procedure, whether electrical and process control upgrades fulfil the legal requirements and can be implemented without reservation. Only then do we issue approval for operation. We do not allow ourselves to…

  • Background articles, Posts

    Safety analyses: The latest methods

    «Nuclear power plants are among the most robust industrial constructions in Switzerland. We ensure that operators constantly question the safety of their installations, calculate any residual risk using the latest methods and constantly improve the resilience of the installations with targeted upgrading. ENSI’s requirements with regard to earthquake safety, for instance, are considered to be…

  • Background articles

    New Nuclear Power Plants

    In 2008, general licence applications were submitted for three new nuclear power plants in Switzerland: the Mühleberg replacement nuclear power plant, the Beznau 1 & 2 replacement nuclear power plants, and a new construction project at Niederamt in the canton of Solothurn. For the purposes of the general licences, ENSI began by examining whether the…

  • Background articles

    Radiation Measurement Technology

    Development and Research Work in the Field of Radiation Measurement Technology: this project deals with the verification and calibration of dosimetry systems and radiation measurement instruments. On the one hand, importance attaches to personal dosimetry, i.e. the measurement of the outer and inner radiation exposure for people.

  • Background articles

    OECD MCCI

    OECD MCCI, Melt Coolability and Concrete Interaction: the OECD MCCI (Melt Coolability and Concrete Interaction) project concerns severe accidents in which the reactor core melts due to the absence of cooling, after which the reactor pressure vessel (RPV) also fails. In the reactor building, the corium reaches the concrete foundation, which should be prevented from…

  • Im August 1955 nahmen Forscher auf dem Gelände des Eidgenössischen Instituts für Reaktorforschung (EIR) in Würenlingen (AG) den „Diorit“-Reaktor in Betrieb.
    Background articles

    OECD CABRI Waterloop Project

    OECD CABRI Waterloop Project: experiments on the high burn-up behaviour of fuel rods in case of rapid reactivity incidents were carried out on the CABRI research reactor in Cadarache, France. These incidents occur when the reactor briefly becomes over-critical due to the rapid, uncontrolled movement of a control element or control rod.

  • Background articles

    Non-Destructive Measurements on the Containment

    Feasibility Study for Non-Destructive Measurements on the Steel Pressure Shell of the Primary Containment of Nuclear Power Plants: the primary circuit, including the reactor pressure vessel, is enclosed by a steel pressure shell as part of the defence-in-depth safety barriers. Depending on the structural design of the nuclear power plant, this is directly surrounded by…

  • Background articles

    PISA

    PISA, Pressure Vessel Integrity and Safety Analysis: in connection with the long-term operation of the Swiss nuclear power plants, it must be proven that the integrity of the reactor pressure vessel (RPV) continues to be guaranteed during normal operation and also in case of operating faults and postulated incidents. The PISA project was launched in…