A nuclear power station may close two years earlier than planned due to ageing issues, an energy firm has said.
EDF Energy was due to begin decommissioning in Hinkley Point B in Somerset in 2023.
Inspections have found cracks in the reactor core's graphite bricks and the boilers inside the reactors were coming to the end of their life.
The company is reviewing the results and will make a decision at the end of the year.
Hinkley Point B, a one gigawatt (GW) plant, began operation in 1976.
EDF Energy has said the number of cracked bricks is well below the tolerance level but this has made the firm reconsider when the decommissioning process can begin.
Normally it takes several years to fully close down a reactor.
Hunterston B in Scotland may also be decommissioned early due to the same issues.
An EDF spokesman said: "Hinkley Point B is due to stop generating in early 2023, though it is possible we may need to move into de-fuelling within the next two years."
Nearly all of Britain's 9 GW nuclear fleet is composed of advanced gas-cooled reactors where the reactor core is built using graphite bricks.
"Based on current forecasts, four of the UK's eight operating nuclear power stations are due to move into decommissioning by March 2024.
"This has been the case for several years," added the spokesman.
EDF Energy is currently building a new plant, Hinkley Point C, which is due to be operational in 2025.
The energy firm is also awaiting a government decision on funding for its Sizewell C project.