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.