ENSI, the Swiss Federal Nuclear Safety Inspectorate is the national regulatory body with responsibility for the nuclear safety and security of Swiss nuclear facilities.
ENSI is the successor body to HSK from whom it took over on 1 January 2009. It has the same remit and staff as HSK but whereas HSK was part of the Swiss Federal Office of Energy, ENSI is an independent body constituted under public law – similar for example to SUVA, the Swiss National Accident Insurance Fund and the Swiss Federal Institute of Intellectual Property.
ENSI is located in Brugg in the canton of Aargau.
ENSI is responsible for the supervision of Swiss nuclear facilities, i.e. the nuclear power stations, the interim storage facility for radioactive waste, the nuclear research facilities at the Paul Scherrer Institute (PSI) in Villigen and the Ecole Polytechnique Fédérale in Lausanne. Its regulatory remit covers the entire life of a facility, i.e. from initial planning, through operation to final decommissioning including the disposal of radioactive waste. Its remit also includes the safety of staff and the public and their protection from radiation, sabotage and terrorism. ENSI is also involved in the transport of radioactive materials to and from nuclear facilities and in the continuing geoscientific investigations to identify a suitable location for the deep geological disposal of radioactive waste.
ENSI supports research into nuclear safety and is represented on more than 70 international commissions and specialist groups working in the field of nuclear safety. It makes, therefore an active contribution to new international safety guidelines. Through its network of contacts, ENSI is in touch with current developments in science and technology and discharges its regulatory remit on the basis of global experience in nuclear energy.
More information
News
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Change in Leadership of the Nuclear Power Plants Division at ENSI
Dr. Annette Ramezanian is stepping down from her position at the Swiss Federal Nuclear Safety Inspectorate ENSI and will leave ENSI on October 30, 2026.
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Commission franco-suisse 2026: cross-border cooperation continues in the interests of nuclear safety
At the 35th plenary meeting of the Commission franco-suisse , held on 24 and 25 June 2026 in Spiez, in the canton of Bern, the French and Swiss delegations discussed recent developments in nuclear safety and set out the priorities for bilateral cooperation for the coming year.
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2025 Oversight Report: Compliance with approved operating conditions
The Swiss nuclear installations complied with the legal requirements for their operation. There were no impermissible releases of radioactive substances into the environment. This is the conclusion reached by ENSI for the 2025 oversight year.
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The International Nuclear Safety Policy Advisors Group INSPAG continues to grow
At its fourth meeting in May 2026 in Schaffhausen, the International Nuclear Safety Policy Advisors Group (INSPAG) welcomed three new members: Italy, South Africa and the United States of America. This brings the total number of members in the network of officials responsible for international affairs to sixteen.
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Federal Council approves ENSI Board’s 2025 activity and business report
The ENSI Board considers ENSI’s oversight of Swiss nuclear installations to be responsible, effective and of high quality.
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25th Austria–Switzerland bilateral meeting: discussion on deep geological disposal, radiation protection and current issues related to nuclear safety
On 27 and 28 May 2026, the Austrian and Swiss delegations held their annual bilateral meeting, during which they exchanged information on various topics, including the progress of the Sectoral Plan for Deep Geological Repositories and radiological monitoring.
Background articles
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Ten Years on from Fukushima (6/6): Conclusions
The disastrous accident in Fukushima Daiichi occurred exactly ten years ago, on 11 March 2011. In the last few weeks, our article serie has highlighted the causes, the sequence and the effects, as well as describing the conclusions that we have been able to draw from the accident.
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Ten years on from Fukushima, the ENSI Board still holds that safety has priority over political or economic interests
Where there are conflicts of interest between politics, safety and profitability, safety must always take priority. This is one of the most important lessons learnt from the Fukushima nuclear accident.
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‘Switzerland is regarded as very reliable in nuclear matters’ – a commentary by former Federal Councillor Doris Leuthard
At the time of the fateful accident in Fukushima, Doris Leuthard was head of the Federal Department of the Environment, Transport, Energy and Communications (DETEC). To commemorate the tenth anniversary of the nuclear disaster, the former Federal Councillor explains why it was essential to provide political support for nuclear safety after the accident.