Inside Sellafield's hazardous nuclear waste site
23 September 2013 Last updated at 06:16 BST
Sellafield has more high-level nuclear waste storage than anywhere else in the UK, and the government has allocated £67.5bn towards a huge clean-up project.
As Calder Hall, it became Britain's first atomic power station in 1954 and, almost 50 years on, it is a place where high level industrial waste is reprocessed and stored.
But the Nuclear Management Partners (NMP) project to tackle the waste is over budget, behind schedule and has faced a catalogue of problems.
As the Nuclear Decommissioning Authority debates whether to renew its contract later this month, Dr Ian Hudson from NMP claims they are back on track.
Inside Out is the first British TV crew to go inside the most difficult and hazardous part of Sellafield's decommissioning site and visit the contaminated open ponds area.
But is sufficient progress being made to make the site safe?