The UK has shut down its oldest operational nuclear reactor, Wylfa 1, on 30 December last year.
Comprising two 490MW units, the facility is located in Anglesey, an island off the northwest coast of Wales.
It generated around 1GW of atomic energy, which sufficed nearly 40% of Wales’ total power demands.
Both the units at the plant entered service in 1971, and was originally due to shut in 2010.
The units at the facility were the last operating ones among the 26 Magnox reactors built across UK, starting in the 1950s.
Magnox had been the operator for the nuclear facility for nearly 45 years.
The second unit, Wylfa 2, has already been closed in April 2012. Fuel rods will be reprocessed and are already being removed from the reactor.
Wylfa 1 was expected to shut down by September 2014, but had continued operations until last week.
Nuclear Decommissioning Authority chief executive John Clarke said: "I am proud of the team’s innovative work that made this extended operational life possible, but the time has come to finally switch her off and move into the decommissioning phase."
Defuelling of Wylfa 1 unit is scheduled to start during mid 2016, while full-scale decommissioning at the entire site, which is expected to be fuel free by late 2018, will last for several decades.
Magnox said: "Wylfa, on Anglesey, was the last and largest in a fleet of 11 UK plants based on the ground-breaking Magnox design that led to the world’s first-ever industrial-scale nuclear power station, supplying the nation with electricity."
The first among the UK plants was the 190MW Calder Hall facility in Cumbria, which started operations in 1956.
Magnox reactors were also exported to Italy and Japan in the 1960s, reported Reuters.
Image: Wylfa nuclear power plant. Photo: courtesy of Magnox.