Having shut down one of the two reactors at Heysham 1 nuclear power station, EDF Energy has announced it has also shut down Heysham 1 Reactor 2 and its sister station of Hartlepool.
The reactor at Heysham 1 nuclear power station had been shut down on 11 June for refuelling and to allow investigations to take place on one of its eight boiler units.
This followed tests which took place during a period of planned maintenance and inspection in 2013.
During the Heysham 1 Reactor 1 planned statutory outage in 2013, an unexpected result was found during routine ultrasonic inspection of a boiler spine.
No similar results were seen on the other seven boiler spines subjected to equivalent inspections on Heysham 1 Reactor 1, or during subsequent equivalent inspections of the boiler spines on Heysham 1 Reactor 2 and at Hartlepool.
Heysham 1 Reactor 1 was returned to service early in 2014 on reduced load with the affected boiler quadrant isolated pending further investigations to confirm the source of the unexpected inspection result.
Subsequent more detailed inspections of the affected boiler spine during an outage on Heysham 1 Reactor 1 that commenced in June 2014 have confirmed a defect in the location indicated by the initial findings.
Heysham 1 Reactor 1 remains shut down while work continues to characterise the nature of the defect.
EDF Energy is unable to say when the reactors will be turned on.
EDF Energy’s other nuclear power stations are not affected by this issue as they are of a different design.
Heysham 1 Reactor 1 is likely to continue to operate on reduced load when it returns to service until a suitable repair strategy can be implemented.