The four cooling towers at Calder Hall in Cumbria, the world's first full-scale nuclear power station, have been demolished.
Hundreds of people gathered to watch as the 88m-high towers on the Sellafield site were detonated in pairs at 0900 BST and five minutes later.
A massive cloud of dust blew over the Irish Sea as they came down.
The towers, which had stood for 50 years, were regarded as a major part of Britain's industrial heritage.
Their dismantling, part of Calder Hall's decommissioning, comes more than four years after electricity generation ceased at the site.
It is the first part of a plan to decommission the complex, comprising 62 buildings, which was opened by the Queen on 17 October, 1956.
Calder Hall, at Sellafield, produced electricity for 47 years
Andy Scargill, the site's decommissioning superintendent, said: "It is a historic day, but it is a day that is bringing together a lot of hard work, a lot of effort and a lot of technical challenges.
"It looks like two minutes' worth of work today but it has taken three years to get to this point."
It will take 12 weeks to remove the rubble from the explosions, with steel from the site being recycled where possible.
The towers contain asbestos and this will be removed during the clean-up operation.
Debris from the towers will be recovered, processed and used to fill in the voids of the cooling ponds beneath the towers, making the site available for reuse in the future.
Plans to create a £128m hi-tech museum at Calder Hall were scrapped earlier this week.
The Nuclear Decommissioning Authority (NDA) said the proposal had been ruled out because of the costs involved, although a spokesman said creating it on the site "was possible".
Permission to decommission Calder Hall was obtained in June 2005, after several years of criticism about the safety of its operation, and a public consultation.
During their operation, the four towers supplied cooled water as it returned to the turbine hall within a closed energy system, a key part of the production of power.
Early in its existence, Calder Hall was primarily used to produce weapons-grade plutonium, with electricity generation as its secondary purpose.