The Autorité de sûreté nucléaire (ASN) — Nuclear Safety Authority — is France's independent administrative authority for civil nuclear safety and radiation protection. Following the "TSN" (Transparence et sécurité en matière nucléaire) law of 2006, ASN has had a high degree of statutory independence.

In 2025 the French government enacted a reform merging ASN with the technical support organisation IRSN (Institut de radioprotection et de sûreté nucléaire) into a single body, the Autorité de sûreté nucléaire et de radioprotection (ASNR). The merged body retains independence and the existing licensing framework.

Mandate

ASN/ASNR oversees the safety of:

  • The 56 operating EDF reactors (mostly PWR 900/1300/1450 MWe units across 18 sites) and the EPR at Flamanville 3.
  • The fuel cycle — Orano (formerly Areva) facilities at La Hague (reprocessing), Tricastin (enrichment, conversion, fabrication via FBFC), Melox (MOX fabrication), and Bessines (uranium ore residues).
  • Research reactors at the CEA (Saclay, Cadarache, Marcoule); fusion research at ITER (under construction in Cadarache).
  • Medical, industrial and research uses of radiation.
  • Decommissioning of legacy fuel cycle facilities and the first-generation gas-cooled reactors.

Regulatory tools

ASN regulates via licensing (decree-level for major facilities, ASN decisions for amendments), inspections, periodic safety reviews (every ten years for operating reactors), and enforcement decisions. Eleven regional Divisions Territoriales conduct on-site inspection work.

Technical analysis is provided by IRSN (now part of ASNR after the 2025 merger), with independent peer review by the Groupes Permanents d'Experts (GPE), standing expert groups that advise ASN.

Stress tests and post-Fukushima evolution

Following the Fukushima Daiichi accident in 2011, ASN required Complementary Safety Assessments (ECS, "stress tests") for all French facilities, leading to the Noyau Dur ("hardened core") programme of additional safety systems resilient to beyond-design-basis external events, plus the establishment of EDF's nuclear rapid action force (FARN).

Long-term operation

France's reactor fleet — built largely in the 1970s and 1980s — has been the subject of intensive long-term-operation review. ASN has been authorising operation beyond 40 years on a unit-by-unit basis after the "fourth ten-yearly review" (VD4), with significant safety upgrades demanded for each life extension.