EDF Energy said on Monday that it had shut down four of its UK nuclear reactors for eight weeks, or roughly a quarter of its total nuclear generating capacity, after discovering a fault in a boiler unit during a routine inspection.
The UK subsidiary of French state-owned utility EDF owns and operates eight nuclear power stations in the country with a combined electricity generation capacity of roughly 8.8m kilowatts – just over 10 per cent of the UK total.
The shutdowns highlight how reliant the UK has become on a fleet of nuclear plants that is nearing the end of its service life. All but one of EDF's plants are scheduled to close by the end of 2023, and the company has been seeking life extensions for many of them.
It is also planning to build a new multibillion pound power station at Hinkley Point C in Somerset, and last year signed an investment contract for the plant with the government guaranteeing it a price for the electricity generated of £92.50 per megawatt hour – roughly twice the current price.
The reactors that are to be shut down are at Heysham in Lancashire and Hartlepool.
EDF said that during a planned outage at one of its two Heysham 1 reactors, an "unexpected result" was found during a routine inspection of a boiler unit. The reactor was returned to service early this year on a reduced load, with the affected part of the boiler isolated pending further tests.
More detailed inspections during an outage that started in June confirmed a defect and the reactor remains shut down.
But EDF Energy said it had taken the "conservative decision" to shut down three other reactors that are of similar design to the affected plant – a second at Heysham and two at Hartlepool. The closures will allow the company "to carry out further inspections in order to satisfy itself and the regulator that the reactors can be safely returned to service", it said.
It added that until the results of more inspections were known, it was not possible to say when the four reactors would return to service: however, an initial estimate suggested the investigations would take about eight weeks. It said its other nuclear power stations were not affected by this issue as they are of a different design.
The defect at Heysham 1 affected what is known as a boiler spine, a central forged metal tube that supports the weight of the boiler tubes around them.