Sodium removal from Phenix secondary loop - 000101

Phenix is a French fast neutron nuclear power plant, cooled with liquid Sodium. It started operating in 1974 on the Atomic Energy and Alternative Energies Commission (CEA) site of Marcoule. Its final shutdown occurred in 2009. To dismantle the three secondary loops (20 inches diameter over several hundred meters) and their auxiliaries in a conventional manner, prior operations of sodium removal are implemented by the operator. The sodium removal process of the secondary loops is carried out in 4 successive stages: 1) the main draining (that is the gravity drain of sodium to storage tanks), 2) additional draining and removal of singularities, 3) carbonation, and 4) rinsing. The carbonation consists in circulation of hot gas through all the pipes. The carbonation is based on the following chemical process, a gas mixture, made up of a sluggish vector gas (nitrogen) of two reactive (CO₂ and Steam), sweeps a surrounding surface containing some sodium. This process neutralizes sodium by converting it into inert sodium carbonates and produces hydrogen. The rinsing process consists of a water circulation in the circuit to dissolve the sodium carbonates. (authors)