British Energy has been granted safety approval to continue operating two of its nuclear power plants for a further 10 years.
Hinkley Point B was due to be decommissioned in 2011
Both Hinkley Point B and Hunterston B - at Somerset and Ayrshire respectively - were closed last summer for repairs.
Extension of the operating licence is subject to the completion of some remedial work at both plants.
The company has agreed to a £4.5m programme of work with the Nuclear Installations Inspectorate (NII).
British Energy said it was continuing to work on graphite and boiler problems and expects to restart the stations this month.
Explicit details of NII's criticisms regarding the plants were not disclosed, but it said it would continue to monitor progress on the action plan agreed between the two groups over the next few years.
This included a "specific fire scenario" which it said should "be investigated with due urgency", although details were withheld.
Shares in the firm surged more than 5% following the safety approval, which means the group could extend the lifespan of the plants from 2011, when they were due to cease production.
British Energy said it would make a decision on this by March next year.