Spewing radioactive contamination around Britain and northern Europe
The Windscale Pile One chimney at the Cumbria plant has been sealed and cut off since the 1957 disaster.
There is still highly charged material trapped inside the shaft of the 400ft chimney, and more than 10 tons of melted radioactive uranium fuel remains inside the structure itself.
The reactor was built after World War II to make some of Britain's first nuclear bombs, and then pressed into service to make tritium for an H-bomb, pushing the reactors beyond their limits and causing the blaze.
Workers at the plant were exposed to 150 times a safe lifetime's dose of radiation, and for a month the government destroyed all milk produced within 200 miles of the site.