The Brennilis nuclear power plant, the only heavy-water reactor in the French nuclear programme, was built between 1962 and 1967, coming into service in 1967. It was shut down permanently in 1985 but decommissioning was not immediate. Bouygues Construction Services Nucléaires was appointed to fully dismantle the heat exchangers and CO2 circuits which cooled the reactor when it was operating.
The CO2 circuits were cut up with an orbital pipe saw. The sixteen 19-m-tall shells each weighed 39 tonnes. Each was separated from its support in turn, removed to another location, and cut in two with a wire saw. Each piece was then turned over and cut into pieces of a size consistent with nuclear waste disposal.