Four nuclear power reactors that were shut down after a defect was discovered in one of them are set to begin switching back on at the end of next month, operator EDF Energy has said.
The firm said a “phased return to service” was expected to take place between the end of October and the end of December.
Power supplied by the reactors at Heysham 1 and Hartlepool, which were shut down last month, accounts for roughly 10% of the UK’s nuclear capacity, enough to supply three million homes.
Earlier this week, National Grid said that uncertainty over electricity supply this winter meant it would take the “sensible precaution” of paying mothballed generators to be online over the period.
EDF said last month that it was shutting down the reactors at Heysham 1, in Morecambe, Lancashire, after a crack was discovered on a boiler spine – a metal tube that supports the weight of the boiler tubes around the reactor.
Hartlepool power station was also shut down because both stations shared the same design. EDF said the design was particular to these sites and not affecting its other nuclear power stations elsewhere in the country.
Engineers must now complete inspections to ensure there are no further defects which could develop into cracks, as well as understanding the cause of the crack found. They must also design and put in place any modifications needed.
They also need to present a safety case for reopening the boilers to satisfy the independent Office for Nuclear Regulation.
EDF said: “Depending on the progress of the programme and any necessary modifications, the company expects there to be a phased return to service between the end of October and the end of December, 2014.
“Dates for returning the stations to service depend on the findings and completion of the inspections. EDF Energy will give further updates on the progress of the programme when it is able.”
EDF Energy’s other nuclear plants are at Torness in Dunbar and Hunterston B in West Kilbride, Scotland; Sizewell B in Suffolk; Hinkley Point B in Somerset, and Dungeness in Kent.
The French-owned firm is leading a consortium which plans to build the new £16 billion Hinkley Point C nuclear plant in Somerset, due to be completed in 2024.
National Grid’s announcement on Tuesday on measures to keep the lights on came after fires at the Ironbridge and Ferrybridge power stations and an announcement that Barking power station was closing, as well as the EDF nuclear shutdowns.
The Grid had set out plans in June to cope with the “energy crunch” when the gap between total power capacity and expected peak demand could shrink to just 2% though had not initially planned to run the scheme this winter.