Three phases can be considered when decommissioning after waiting 10 years or so:
- Final shutdown
The first operation to be carried out is removal of the spent fuel from the vessel, and drainage of all the systems (in this way 99% of on site radioactivity is eliminated), followed by decommissioning of the conventional facilities for electricity generation.
- Partial decommissioning
The second stage involves demolishing the equipment and buildings (excluding the reactor building), conditioning of all waste and sending it to special repositories. At this stage the reactor building is monitored.
- Full decommissioning
The final stage involves completely demolishing the reactor building and dismantling all materials and components with residual radioactivity, together with the waste produced by these activities. At this point, the site can be defined as a “green field”.
All these operations are governed by radioprotection regulations which prohibit dispersion of radioactive material in the environment.
Decommissioning has been completed for several nuclear power plants throughout the world (10 plants in the USA, the Berkeley and Trawsfynydd plants in the United Kingdom) therefore decommissioning is not uncertain from the point of view either of technical feasibility or of related costs.