British Energy has announced that it is hoping to extend the life of the Hunterston B nuclear power station.
Hunterston B had been due to close in 2011
The Ayrshire station may now stay open until the year 2021. The move could secure the future of about 700 jobs.
The plant is working on the 10-year extension proposal. A final decision will be taken in 2008.
Meanwhile, Scottish Power is spending £170m on emission improvements to extend the life of the Longannet coal-fired power station in Fife.
The Longannet modernisation would mean it could avoid closing when new limits on pollution come into force in nine years' time.
The station produces about a quarter of Scotland's electricity.
Operator Scottish Power is to install special equipment to remove the sulphur from emissions.
A spokesman said that filters would remove about 94% of the sulphur, meaning the plant could massively increase the amount of Scottish coal it used.
Construction work will last for two years and it is hoped it will secure about 300 jobs.
Friends of the Earth Scotland said the move laid to rest speculation that Scotland would need a revival of nuclear energy.
Chief Executive Duncan McLaren said: "By the time Longannet finally closes, renewables - on and off-shore - energy efficiency and carbon capture technologies will easily be able to deliver all the electricity Scotland needs, and a healthy surplus for export."
The UK Government is currently carrying out a major review of energy policy.
It is looking at predicted future energy requirements and how power might be generated.