The inspection will cut over a quarter of the UK’s nuclear fleet from service, or 2.5 GW of power from the UK energy mix.
The operator first discovered a fault in the boiler spine of one of the Heysham nuclear units during a maintenance period in 2013. Further investigations continued this year while the unit ran at reduced load, and with the affected boiler isolated, before a maintenance outage in June confirmed the defect.
The operator has now opted to perform a full inspection of the affected 660 MW Heysham 1-1 reactor as well as those of a similar design, including: the 610 MW Heysham 1-2, 620 MW Hartlepool 1 and 620 MW Hartlepool 2 nuclear units.
EDF Energy said it will begin inspections of the reactors over the coming days “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,” the company said.
Investment analysts at RBC Capital said the shutdown will negatively affect the earnings of both EDF Energy and 20 per cent stakeholder Centrica.
“We estimate that the shortfall could impact EDF to the tune of €150 million at the EBITDA line in 2014, and we remind our readers that Centrica holds a 20% stake in British Energy and has confirmed that this will be an impact of 0.3p/share on current 21-22p 2014 guidance,” the analyst note said.