What types of facilities and what stakes? With the exception of pressurised water reactors (PWR) in NPPs, which are all designed using the same model, most BNIs* undergoing decommissioning represent a variety of technologies, uses and past histories which often complicate the decommissioning operations. There is significant operating experience feedback for decommissioning of research reactors, owing to the decommissioning of numerous similar installations in France, notably on CEA’s Grenoble site. During the course of decommissioning, the radioactivity risks rapidly give way to conventional industrial risks, for example the chemical risk during the clean-out phase, or that linked to the management of several simultaneous worksites. Pressurised water reactors After decommissioning of the Chooz A reactor (Ardennes département**), which began in 2007, decommissioning started on the two reactors of the Fessenheim NPP (Haut-Rhin département), which was shut down in 2020. There is considerable operating experience feedback from PWR decommissioning: 42 PWRs are being decommissioned worldwide in 2021. There are no major technical difficulties in the decommissioning of these installations, which takes about twenty years. Other reactors In France, several NPP reactors undergoing decommissioning were based on technologies no longer in use: gas-cooled reactors (GCRs – located in Bugey, Chinon and Saint-Laurent-des-Eaux), heavy water reactor (Brennilis), fast breeder reactors (Phénix and Superphénix). For these reactors, some of which have not been operating for several decades, there is no significant operating experience feedback, unlike with the PWRs. The fact that they are unique means that specific and often complex decommissioning operations must be designed, such as specific remote-operated systems. NUCLEAR POWER REACTORS Different reactor technologies have been used to produce electricity in France. Their decommissioning must take account of their specific characteristics. As of the final shutdown of these reactors, removal of the fuel is a means of achieving a 99% reduction in the radioactivity present in the installation. RESEARCH REACTORS These are characterised by a far lower power level than nuclear power reactors (from 100 Watts thermal – Wth – to 70 Megawatts thermal – MWth). Nine experimental reactors, operated by CEA, are currently definitively shut down; when they were designed back in the 1960s to 1980s, the question of their decommissioning was not considered. * See glossary page 30 ** Administrative region headed by a Prefect. 8 • Les cahiers de l’ASN • June 2022 THE DECOMMISSIONING FRAMEWORK
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