CRACKS have been found in the reactor core at Hunterston B nuclear power station, raising question marks over the future of the ageing plant.

The defects were found during an inspection as part of the recent planned shut down of the reactors.

Two cracked graphite bricks were found in reactor 4 which is made up of 6,000 bricks.

Bosses at the 38-year-old plant were quick to play down any risks to safety – and insist the cracks are ‘in line with expectations’.

Colin Weir, Station Director at Hunterston B said on Tuesday: “Every time we take the reactor out of service for planned maintenance, we inspect the graphite core.

“During the current Hunterston outage we found two bricks with a new crack which is what we predicted during Hunterston B’s lifetime as a result of extensive research and modelling.

“It will not affect the operation of this reactor and we also expect that a few additional cracks will occur during the next period of operation.

“The small number of cracked bricks found during routine inspection is in line with our expectations.

“The findings have no safety implications and are well within any limits for safe operation agreed with our regulator.” The power plant which employs 520 people was scheduled to close in 2011 but has had its life extended to 2016 and could remain operational until 2023 if owners EDF Energy gets their way.

Critics of nuclear power have called for it to be phased out and the move to renewable energy sources hastened.

Yvonne McLennan, co-convener of the Ayrshire branch of the Scottish Green Party commented: “The new cracks that have been discovered at the nuclear reactor at Hunterston B are a sign that the future of these facilities is becoming unreliable.

“Should further cracks appear, the potential risk of core distortion is simply unacceptable.

“We should be harnessing the further growth in our renewable capacity with a view to increasing it to a stage of being able to switch from nuclear power to renewables on a permanent basis.

“This added to the prospect of waste being transported in lorries through the central belt from Torness in East Lothain, paving the way for others, to Hunterston all makes for an intolerable situation for those living within Ayrshire.” A spokesperson for the Office for Nuclear Regulation said: “ONR is satisfied with EDF Energy’s response to the discovery of the cracks and their subsequent evidence that there is no immediate safety significance for Hunterston B.

“ONR recently issued consent to restart Reactor 4 following its statutory outage.” The plant’s reactors are now back in service, although it is not yet supplying electricity to the grid due to a lead time after start-up.