The Eidgenössisches Nuklearsicherheitsinspektorat (ENSI) — Swiss Federal Nuclear Safety Inspectorate — is Switzerland's independent regulator for nuclear safety and security at civilian nuclear facilities. It is headquartered in Brugg, Canton Aargau, near the country's reactor sites.

Mandate and history

ENSI was created on 1 January 2009 by the Federal Act on the Swiss Federal Nuclear Safety Inspectorate (ENSIG, SR 732.2). It replaced the previous Federal Nuclear Safety Inspectorate (HSK) and is now an independent public-law institution with its own legal personality. The federal government's role through DETEC (Department for the Environment, Transport, Energy and Communications) is limited to strategic oversight; technical regulatory decisions are made by ENSI itself.

Legal framework

The Swiss nuclear regulatory framework comprises:

  • Kernenergiegesetz (KEG, SR 732.1) — Nuclear Energy Act (2003, in force from 2005).
  • Kernenergieverordnung (KEV, SR 732.11) — implementing regulation.
  • ENSIG (SR 732.2) — establishing ENSI.
  • Strahlenschutzgesetz (StSG, SR 814.50) — Radiation Protection Act, with corresponding StSV regulation.
  • ENSI's own guidelines (ENSI-A, ENSI-B, ENSI-G series) covering specific technical and management topics.

Facilities supervised

Switzerland operates four power reactors:

  • Beznau 1 and 2 — two-loop PWRs (Westinghouse), commissioned 1969/1971. Beznau 1 is the world's oldest operating commercial reactor as of mid-2020s.
  • Gösgen — PWR (Siemens-KWU), commissioned 1979.
  • Leibstadt — BWR (GE), commissioned 1984.
  • Mühleberg — BWR, permanently shut down 2019, decommissioning supervised by ENSI.

ENSI also supervises the Paul Scherrer Institute (research reactors), Zwilag (the central interim storage facility), and a planned deep geological repository under the Federal Council's 2022 selection of Nördlich Lägern (NAGRA) as the host site.

Energy phaseout

The Swiss electorate voted in 2017 to ban construction of new nuclear power plants; the existing reactors may continue to operate as long as they remain safe. ENSI is responsible for the technical safety case for each year of continued operation and for the eventual decommissioning of every facility.