As early as 1946, some uranium was discovered in France by the CEA, but France did not master the technology of isotopic enrichment, still a US monopoly at the time. Consequently, the French designed, developed and deployed a first generation of nuclear power plants which did not require enriched uranium as a fuel: the so – called UNGG (for Uranium Naturel Gaz Graphite), similar to the British Magnox. The very first nuclear electricity was generated in France in October 1956, in G1, an experimental reactor operated by the CEA. But the first commercial nuclear plant operated by EDF, the 70 MWe UNGG “Chinon A1”, began generating power feeding the French grid in 1963.
The spent fuel from Magnox and UNGG reactors cannot be stored very long under water and must be reprocessed to stabilize the High Level radioactive waste it contains. The French therefore developed the reprocessing technology, recovering the residual uranium and the plutonium contained in the spent UNGG fuel. Anticipating a vigorous increase for nuclear electricity production, it was then thought that the plutonium would very soon be needed to fuel the Fast Neutron Breeder FBR, a type of reactor which technically is more complex but can extract energy from uranium much more efficiently. Logically enough, the French realised in 1973 the first actual breeder, the 250 MWe demo FBR, Phenix, still operating today (the plant is due to be shutdown in 2009 and then will be decommissioned).
By 1970, EDF was operating 6 UNGG plants, an experimental heavy water gas cooled plant (with the CEA) and, together with Belgium, a 300 MWe PWR, Chooz A1. The capacity of the plants (totalling 3 GWe) supplied 8% of the French electricity consumption. At a time when each new nuclear power plant in the western world was a unique prototype, EDF had notably taken the very unusual decision to order its last two plants as identical twins (in fact it was a series of three identical plants, the third one of this kind being built in Spain). This decision marks the first stage of what will become a main characteristic of the French industrial policy: increasing exploitation efficiency through standardisation.
In the meantime, the CEA had developed the gaseous diffusion technology to enrich uranium for Defence programs. Over the world, most utilities were now buying Light water plants, PWR and BWR of American technology. LWRs are far more compact than UNGG, which results in lower capital costs, but they require a fuel enriched to 3 to 4% 235U.
So, in 1970, EDF took the first momentous decision to discontinue the “French” reactors series, and to acquire LWRs from US origin from then on. The US enrichment monopoly having been broken was no longer a political issue. The French company Framatome acquired the PWR license from Westinghouse while Compagnie Generale d’Electricite took the GE license for BWR. EDF was planning on ordering from either company about one 900 MWe LWR per year, starting with 2 PWR in Fessenheim and 1 PWR in Le Bugey. Consequently, CEA started adding a new Head-end to its La Hague commercial reprocessing plant to accommodate much more radioactive LWR spent fuel.