EDF Energy, the British unit of French giant EDF, said on Monday it had decided to shut down four nuclear reactors at two plants in northern England as a precaution.
EDF Energy said it was shutting down two reactors at each of the Heysham and Hartlepool nuclear plants for at least about eight weeks.
It follows a defect at one of the four reactors, which has kept it out of action since June. The decision to shut down an additional three reactors was described as a "conservative decision" in a statement issued by EDF Energy.
It comes as Britain's government is placing nuclear power at the heart of its low-carbon energy policy, in stark contrast to Europe's biggest economy Germany, which vowed to phase it out in the wake of Japan's 2011 Fukushima disaster.
Last year, Britain signed a £16-billion deal with EDF to build two reactors at Hinkley Point C, southwestern England, to help meet the country's future energy needs.
Also involved in the contract are French group Areva -- the world's leading nuclear power company -- and Chinese nuclear firms CGN and CNNC.
EDF Energy meanwhile said in a statement on Monday that its Heysham 1 Reactor 1 "remains shut down while work continues to characterise the nature of the defect" detected earlier this year.
"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," it said.
"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 statement added.
In a separate statement, British energy group Centrica said the shutdowns announced on Monday would impact its own earnings this year owing to its 20-percent interest in EDF Energy's existing nuclear operations.
"On this basis, the resulting reduction in output from the affected nuclear power stations is currently estimated to reduce Centrica's earnings per share in 2014 by around 0.3 pence per share," it said.
Centrica's share price was little changed following the announcement, with the company trading down 0.06 percent at 307.7 pence in London. EDF Energy parent EDF was also flat at 23.8 euros in Paris deals.