French power company EDF Energy has decided to keep one of the two reactors at its Hunterston B nuclear power station offline.

Inspectors had discovered fresh cracks in the core of reactor three, which had been expected but which were happening at a “slightly higher rate” than predicted in computer models.

Power output from the power station in Ayrshire will be cut by up to 40% this year to 3TWh.

The company said the operation of its other plants would not be affected.

£100m spent

EDF said: “We have been working over many years to fully understand and prepare for these late life changes to the reactor core and regular inspections at all our plants have provided a clear understanding of how the reactor cores age.

“The longer-term safety case will build on work already completed and EDF Energy expects that this will demonstrate that there are large safety margins both now and for the projected reactor lifetime.

“Over £100m has been spent on the graphite research programme which benefits from the expertise of our own team of specialists as well as academics at several leading UK universities.”

> See EDF's statement