Cracks in the core of a Scottish nuclear reactor could signal that most of Britain's aging plants will not be able to supply the country with much-needed power for as long as predicted.

Nuclear reactors generate just over 20 percent of Britain's electricity, and even before EDF Energy said last week it would need to shut down one of two reactors at the Hunterston B plant, almost half of that capacity was scheduled to go offline by 2025.

"These reactors are over 40 years old. This is a generic defect which cannot be fixed, so it would not surprise me if the older plants would all need to close within the next few years," said John Large, an independent nuclear engineering consultant.