Swiss federal authorities

Events

ENSI combines events and findings under the term “events”. Both events relevant to nuclear safety and security and events of public interest are subject to reporting. The latter includes events on the site of the nuclear installation that are perceptible from outside the site boundaries, regardless of their importance for nuclear safety.

ENSI informs the public in its annual oversight report about all reportable events pertaining to nuclear safety and security.

ENSI continually publishes information on its website about events that meet one of the following criteria:

  • INES Level 1 or higher (International Nuclear and Radiological Event Scale),
  • Triggering of safety systems,
  • Incidents that would lead to core damage with a probability of more than 1 in 100 million,
  • Incorporation of radioactive substances with a dose commitment of more than 1 mSv.

Events in Swiss Nuclear Power Plants

  • Events, Vorkommnisse Mühleberg

    KKM: Possible Blockage of the Special Emergency System Water Intake in case of Extreme Flooding (as at: 07.10.2011)

    As a measure following on from the reactor accident at Fukushima, Japan, ENSI ruled on 1 April 2011 that the Swiss nuclear power plant operators must furnish proof of their ability to control a very unlikely extreme flood, and must do so by the end of June 2011.

  • Events, Vorkommnisse Leibstadt

    KKL: Automatic Turbine Shutdown (as at: 30.06 2011)

    A faulty resistor on an electronic card led to the failure of a module in the turbine control system. As a result, the control dampers on the low pressure turbines closed slowly.

  • Events, Vorkommnisse Leibstadt

    KKL: Weld Seam Leak on Small-Bore Pipe of the High Pressure Core Spray (CS) System (as at: 13.04.2011)

    During a function test on the high pressure core spray (CS) system, a thin jet of water was detected. This jet emerged from a weld seam on a small-bore pipe leading to a safety valve. The function test was interrupted, and the affected section of the small-bore pipe was replaced within the permissible time for…

News

  • News, Posts

    2023 Oversight Report: The safety status of the nuclear power plants is good

    ENSI verified the status of the Swiss nuclear power plants by 327 inspections. In 2023, the year under review, 22 reportable nuclear-safety-relevant incidents were recorded at the nuclear power plants. ENSI provides detailed information in the oversight report published today.

  • News, Posts

    Quality assurance errors relating to some fuel rods in the Leibstadt Nuclear Power Plant

    A few days ago, Leibstadt Nuclear Power Plant (KKL) informed the Swiss Federal Nuclear Safety Inspectorate (ENSI) that some fuel elements do not fulfil the requirements of the applicable specifications. Accordingly, KKL decided to replace them for safety reasons. The safety of man and the environment was ensured at all times.

  • News, Posts

    “Cladding tube damage poses no risk to mankind or the environment”

    The Swiss Federal Nuclear Safety Inspectorate (ENSI) has issued Leibstadt Nuclear Power Plant (KKL) approval to restart subject to conditions. The conditions under which dryouts have occurred at KKL are known. KKL has instigated counter measures. Consequently operation is safe. In an interview Ralph Schulz, Director of the Safety Analyses Division, shares some background insights.

  • News, Posts

    Findings on fuel elements in Leibstadt NPP: ENSI is classifying the incident as INES 1 and checking the submitted measures

    An inspection of fuel elements in Leibstadt NPP revealed that critical boiling states – so-called dryouts – had systematically occurred over several cycles. The Swiss Federal Nuclear Safety Inspectorate (ENSI) is classifying this incident as Level 1 on the International Nuclear and Radiological Event Scale (INES). It is currently checking the documents and actions submitted…

Documents