THE chairman of Hunterston site stakeholders group has called upon the power station’s Reactor 3 to remain closed as a result ofthe increased number of cracks found in graphite bricks.

It has been revealed that over 350 cracks have now been found, with concerns being raised as to the future operation of the plant.

However, owners EDF Energy closed reactor 3 earlier this year to carry out a more in-depth investigation, and have given assurances that the cracks are ‘much narrower’ than set out than the safety parameters set which considerably lessens any danger.

Rita Holmes, chair of the Hunterston Site Stakeholder Group, said “If safety were indeed EDF’s number one priority, then reactor three would remain shut down.

“As it is EDF is seeking permission to restart an aged reactor, which despite huge efforts and high cost, failed to back up its current safety case. The Hunterston keyway root cracking was not predicted to be so progressed.

“There’s a lot at stake if the experts are wrong again.”

However, EDF Energy insist that it remains safe to operate, and it is planned that both reactors will be back online in the coming months.

An EDF Energy spokesperson said: “The cracking only poses a potential challenge to the entry of the control rod in an ex treme and highly unlikely (1 in 10,000 year) earthquake scenario and even then we have back-up systems which include super articulated control rods (designed to bypass distortions) and nitrogen plant which could be injected within seconds to shut-down the unit.

“Nuclear safety is our overriding priority which is why we have carried out the most extensive inspection programme on an AGR station to date at Hunterston B.

“During the most recent inspection of Reactor 3 we examined around a quarter of the core. As expected we identified a number of new cracks. This number exceeded the operational limit of the existing safety case but was significantly mitigated by the cracks being much narrower than modelled in the safety case; something which was reported to the local site stakeholder group in June of this year.

“The most recent results support the work we are doing on the long-term safety case and underline our confidence that the normal operations at the station are unaffected and that there would be safe shutdown in the event of a 1 in 10,000 year earthquake. We are preparing to present a safety case for return to service of Reactor 3 to the regulator, the ONR, for their assessment. We have also carried out similar inspections on Reactor 4 and the case for return to service for that unit is currently with the ONR for review.”

The return to service dates for the units which are cur rently on the REMIT website: Reactor 3 – 21 Feb 2019 and Reactor 4 – 14 Jan 2019.

EDF added: “Graphite inspection work on both reactors at Hunterston B is now complete. We are preparing to present a safety case for return to service of Reactor 3 (turbine generator 7) to the regulator, the ONR, for their assessment. The case for return to service for Reactor 4 (turbine generator 8) is currently with the ONR for review. We have updated REMIT to reflect the further time needed for the preparation and assessment of the safety cases.”