EDF Energy previously advised that one of the two reactors 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. EDF Energy is now issuing an operational update concerning Heysham 1 and its sister station of Hartlepool.
During the Heysham 1 Reactor 1 planned statutory outage in 2013, an unexpected result was found during routine ultrasonic inspection of a boiler spine (see Explanatory Note below). 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 (the design of the boilers being unique to Hartlepool and Heysham 1). 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.
Although routine inspections of other boiler spines have not previously indicated any similar defects EDF Energy has taken the conservative decision to shut down Heysham 1 Reactor 2 and Hartlepool Reactors 1 and 2 that are of similar design over the next few days to carry out further inspections in order to satisfy itself and the Regulator that the reactors can be safely returned to service. Until the results of the further inspections are known it is not possible to advise exact return to service dates for these four reactors, however, an initial estimate is that these investigations will take around eight weeks. 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.
As a result of these further inspections at Heysham 1 and Hartlepool with an initial estimate of around eight weeks the revised likely maximum theoretical output before unplanned losses for the EDF Energy Nuclear Generation Fleet in respect of the period from the 1 January 2014 to 31 December 2014 inclusive will now be c61TWh.
The Company will give a further update in due course.