Upon completion of their operating period, basic nuclear installations (BNIs) undergo a series of clean-up and transformation operations allowing final shutdown prior to decommissioning. The work thus performed may result, from the administrative standpoint and depending on the subsisting activity level, in the creation of a new BNI, in the delicensing of the BNI concerned into an installation classified on environmental protection grounds (ICPE) which has to be licensed or registered, or simply in a return to the public sector (for uses which may or may not be restricted), subject to possible adjusted encumbrances.

The first steps lead to removal of the fuel or nuclear materials present in the facility, which already helps reduce the risk from the nuclear safety viewpoint. This is then replaced by human radiation protection and conventional safety-related risks owing to work being done close to residual nuclear material and the numerous handling operations for removal of the waste generated by decommissioning.

The Nuclear Safety Authority (ASN) now strives to integrate relevant experience feedback from past decommissioning projects in France and abroad. The ASN encourages complete decommissioning either immediately or after slight postponement, provided that upstream of the regulatory processes, the licensee is able to present and justify the chosen decommissioning scenario, from the final cessation of production up to the final decommissioning of the installation. Regulatory practices concerning BNI decommissioning operations were updated along these lines in early 2003.

The ASN considers the current decommissioning operations as test cases, providing an opportunity for the licensees, on the one hand, to define and implement a decommissioning strategy (decommissioning level to be reached, detailed operating schedule), and, on the other hand, a management policy for the large amounts of radioactive waste that will be generated (notably the very low level waste). If carried through to their conclusion, they would also constitute examples demonstrating the technical and financial feasibilities of an entire decommissioning operation.