EDF Energy is shutting down four of its nuclear reactors in the UK as a precautionary measure after a defect was found in one of them.
The decision came after EDF had detected a recurring problem at one of its Heysham 1 reactors earlier this year. The company will now close also the second Heyshem 1 reactor and additional two reactors at its site in Hartlepool, all of which feature identical design.
The affected four reactors together provide about 8.8 million kilowatts, enough to supply three million homes.
EDF first detected problems at Heysham 1 during regular maintenance last year when an ultrasonic inspection of the reactor’s boiler spine, a supporting metal tube holding the weight of the reactor, revealed ‘unexpected results’.
Subsequently, the second Heysham 1 reactor, as well as the two reactors at Hartlepool, was examined but no abnormalities were found.
The first Heysham 1 reactor returned to service in January 2014 on a reduced load but was turned off again in June due to further anomalies.
EDF has now decided that despite the previous all clear, the other three reactors will be shut down this week for further inspections, expected to take up to eight weeks.
The National Grid, which runs the UK power network, said the outage won’t affect electricity supplies as there is "a lot of surplus capacity in the system in the summer to handle this outage".
However, the two-month shut down takes the inspection to October when consumer demand begins to pick up.
The power stations at Heysham and Hartlepool were built in 1983 and are set to be decommissioned in 2019. They were originally due to come out of service this year.
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 company said the issues found at Heysham and Hartlepool are unique to those sites.
EDF added that the two-month shutdown would reduce the firm's annual nuclear power generation by 3.2 per cent to 61 terawatt hours during the year.
Centrica, the owner of British Gas which has a 20 per cent stake in EDF Energy's existing nuclear operations, said the reduction in output from the affected nuclear power stations would reduce the company's 2014 earnings by roughly 0.3p per share.
EDF Energy is leading a consortium which plans to build the new £16bn Hinkley Point C nuclear plant in Somerset, due to be completed in 2024. The project will create 25,000 jobs during construction as well as 900 permanent jobs during its 60-year operation.