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The dismantling of nuclear power plants

The dismantling process comprises all of the technical operations undertaken to clean up a decommissioned nuclear installation by eliminating the hazardous substances as well as the structures and equipment that contained them. (1)
For a nuclear power plant, this includes the disassembly and processing of all components, including the reactor, and their transfer to a suitable storage site.
In France, EDF is managing the dismantling, now in progress, of its nine industrial reactors that have been permanently shut down: Brennilis, Bugey 1, Chinon A1, A2 and A3, Chooz A, Creys-Malville (SUPERPHENIX) and Saint Laurent A1 and A2.
The dismantling operations are scheduled after the final shutdown and decommissioning phases, which take about 10 years. During the shutdown phase the plant is taken offline, its fuel is removed and its circuits are drained. The fuel is then stored in a spent fuel pit for two years while studies are conducted in preparation for decommissioning.
The decommissioning phase is the point of no return, and must be approved by the government. It consists of disassembling all the equipment and industrial structures that will essentially produce conventional (non-radioactive) waste. This conventional waste is recycled and the nuclear waste is packed in containers and evacuated to suitable storage centers. During this phase, studies are conducted to determine how to proceed with the dismantling in compliance with safety goals. Based on these studies, a new government decree authorizes dismantling, which includes disassembling the reactor building, removing the equipment that is still radioactive, and evacuating the waste to a storage site. The duration of this phase is also estimated at about 10 years, ending with a final decontamination operation. This is followed by the surveys, measurements and impact studies needed to compile the decommissioning report, a process that takes another few years.
The dismantling of the nine French reactors is expected to produce 800,000 tons of conventional waste, which will be recycled, plus 165,000 tons of radioactive nuclear waste. (2)
Once all the dismantling phases have been successfully completed, an installation can be officially decommissioned. It is then removed from the list of nuclear facilities and the site becomes available for other industrial uses. (3) Several other installations are now in the process of being dismantled or decommissioned, including research reactors at the French Atomic Energy and Alternative Energies Commission (4) as well as the reactor jointly operated by CNRS and the University of Strasbourg.
All of these operations are carried out within a strict regulatory framework, in particular in compliance with the so-called “TSN law” on nuclear transparency and safety (N° 2006-686, 13 June 2006).
In France, based on figures provided by the operators (EDF, Areva and the CEA), the Cour des Comptes (public audit authority) assesses the cost of dismantling the 58 reactors currently in operation at just over €18 billion (5). However, estimates using other countries’ guidelines result in higher figures. Applying international data to the 58 French reactors gives figures ranging between €20 billion according to Belgian guidelines, and more than €60 billion according to German guidelines. (5) A statement issued by the French Nuclear Safety Authority in April 2011 recommended improvements to the methods used to calculate this expenditure. The cost of dismantling a nuclear installation depends on a number of criteria, including the length of the demolition process and whether or not dismantling begins immediately after electrical production comes to a halt. (3)
Several power plants in the United States have already been decommissioned, such as the Maine Yankee site, which was dismantled between 1997 and 2005. The site has been restored, but the long-term storage of its long-lived radioactive waste has yet to be resolved. (6)

Sources
1/ Website of the French Nuclear Safety Authority
2/ Le Programme de Déconstruction (“Demolition Program”), Le Financement (“Financing”), Les Contrôles et la Transparence (“Inspections and Transparency”) - EDF website
3/ Article in Les Echos: Vrais Comptes et Mécomptes du Coût de Démantèlement des Centrales Nucléaires en France (“Calculations and Miscalculations of the Cost of Dismantling Nuclear Plants in France”), 8 September 2011
4/ Nuclear decommissioning - wikipedia
5/ Report by the Cour des Comptes: Les Coûts De La Filière Électronucléaire (“Costs of the Electronuclear Power Industry”), January 2012"
6/ article "Maine Yankee Nuclear Power Plant" - wikipedia and Maine Yankee decommissionning overview"