Cracks have been discovered in insulation bricks which surround the core of one of Scotland’s two nuclear power stations.
However, the industry safety watchdog said these cracks do not pose an immediate safety risk and the atom plant continues to generate electricity.
EDF – the nationalised French state operator which owns the 40-year old Hunterston-B nuclear plant in Ayrshire – said the cracks in three graphite bricks were found during planned maintenance on Reactor Three.
The firm insisted there were no safety implications and the finding had no impact on the operation of the reactor.
Station director Colin Weir said: “Nuclear safety drives everything we do. This means we work within very large safety margins. This applies to graphite bricks too.
“The level of cracking which is considered reasonable is far below anything which would affect the reactor’s safe operation.
“It is accepted by our regulators and materials experts that cracks will occur in some of the bricks and that the core will lose some of its mass as part of the normal ageing process.”
“The observations were anticipated and are in line with our understanding, so our view of the best estimate lifetime planning date of 2023 has not changed.”
Hunterston-B began operating in 1976 and its working life has already been extended to 2023 – well beyond its first-planned closure date.
A spokesman for the UK Office of Nuclear Regulation – the industry watchdog – said: “It is acknowledged that graphite within the core is subject to weight loss and cracking and that these phenomena do not necessarily pose an immediate safety risk.
“We require the licensee, EDF Energy Nuclear Generation to demonstrate through their safety case that they have adequate understanding of the graphite behaviour to justify safe operation of the core in a clear, evidence-based manner.
“We require EDF NGL to clearly define conservative limits of operation based on the extent and adequacy of their understanding of graphite core ageing.”
Scottish Energy Minister Fergus Ewing said: “The reactor operator has provided assurances that there are no immediate safety implications affecting Hunterston-B, and that it is safe to continue generating electricity.
“However, these cracks illustrate that Scotland’s nuclear facilities have a limited lifespan and we need to put in place longer term energy alternatives.
“Just yesterday the UK Government recognised belatedly that its policies have weakened energy security and pushed up bills but they continue to miss opportunities to put in place new plans to address the gaps in UK energy policy, with few if any new actual incentives to drive energy generation.
“Their policy is inconsistent in terms of getting the best deal for bill payers, incoherent in terms of reducing carbon emissions and is proving ineffectual in terms of ensuring security of supply.
“The Scottish Government is opposed to the building of new nuclear capacity in Scotland, as it would divert billions of pounds away from renewable alternatives where Scotland has a key competitive advantage.
“Subject to strict safety considerations, extending the operating life of Scotland’s existing nuclear stations can help to maintain security of supply while the transition to renewables and cleaner thermal generation takes place.”
* The Office for Nuclear Regulation is currently recruiting for nuclear safety and security inspectors across all disciplines including information and cyber security, radiation protection, civil engineering and transport inspection and enforcement.