The life of Scotland's Hunterston B nuclear power station is to be extended by five years.
The announcement means hundreds of jobs will be safeguarded in Ayrshire.
British Energy said both Hunterston and Hinkley Point B in Somerset will continue to 2016.
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The two sites, which are currently running at around 60% capacity because of boiler problems, began generating power in 1976. Further studies will be conducted by 2013 regarding the potential for additional life extensions beyond 2016.
Tom Ungi, station director at Hunterston B, welcomed the announcement.
He said: "This is great news for all of us at Hunterston B and for everyone in the local North Ayrshire community.
"The decision means we can continue to provide highly skilled jobs and bring major investment to the area. It also shows that British Energy recognises the professionalism and commitment of our staff in safely supplying low-carbon electricity for more than 30 years."
The station employs around 520 full-time staff, as well as 150 employees from contract partners.
British Energy estimates the plant contributes £55m a year to the local economy.
Jim Mather, Scotland's Enterprise Minister, said the Scottish Government was not opposed to extending existing nuclear power stations until the end of their natural life.
However, the Nationalist MSP claimed Scotland does not need or want new nuclear power stations.
"We've got installed renewable capacity already greater than the capacity of nuclear and the fact is that we can achieve secure, clean, low-carbon energy through harnessing those vast resources," he added.
"But the fact here is that this decision would mean that the company will have to invest significantly more at Hunterston to ensure that it is safe and reliable and that has to be in Scotland's interests."