The go-ahead has been given for the decommissioning of Hinkley A nuclear power station in Somerset.
The plant was closed in 1999
Owners British Nuclear Fuels (BNFL) say demolition of the site can now begin as work to remove fuel is already under way.
But some medium-level nuclear waste will continue to be stored there, and the reactors will remain for the next 100 years before they can be dismantled.
Hinkley A opened in 1965 and has been the scene of some anti-nuclear demonstrations to close it down.
Station manager Joe Lamonby said: "Obtaining permission to start decommissioning is a major milestone for the station.
"A lot of planning has been going on, but this means we can physically move things on."
The decision to decommission the plant was taken by the Nuclear Installations Inspectorate, part of the Health and Safety Executive.
BNFL will carry out the decommissioning, overseen by the Inspectorate and the Environment Agency.
The plant has been closed since April 1999.