.	Decommissioning
•	During dismantling
•	Immediate or deferred dismantling
•	Regulatory requirements
•	Stages
•	Summary
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After operating for a certain period of time, nuclear power plants, like any other industrial facilities, become obsolete. They must then be replaced by more modern or more suitable units, and then dismantled. The Nuclear Operating Organization is responsible for all operations up to total dismantling.

After the decommissioning of the plant, even after the removal of the fuel assemblies and other radioactive substances, such as waste, a residual amount of radioactivity still remains due to the following:

• Contamination of the facilities and equipment by variable quantities of radioactive particles and dust which have been deposited in different areas during the service life of the facility
• Residual irradiation due either to the activation of certain structures exposed to the reactor core neutron flux, or local deposits of radioactive substances which could not be eliminated during the decommissioning operations

Furthermore, radiological protection measures, such as decontamination and the use of robots, are implemented to limit the exposure of workers.

At each stage of dismantling, safety is assured by implementing the principle of defense in depth and is subject to regulatory requirements.