From the BBC.
The Thorp nuclear reprocessing plant at Sellafield, Cumbria, has recycled its final batch of reactor fuel. But it leaves behind a hugely toxic legacy for future generations to deal with.
So how will it be made safe?
It is a dangerous job that will take decades to complete and require a great deal of engineering ingenuity and state-of-the-art technology - some of which hasn't even been invented yet.
Reporter: Theo Leggett, video journalist: Rob Wood