Nuclear reactors that generate more than 25 per cent of Britain's nuclear output remain closed today after maintenance problems emerged at three plants adding to two plants already operating under capacity.
Two reactors at the Hartlepool power station were closed at the weekend after corroded steel wire was discovered in the concrete casement of one of the reactors. Meanwhile, both reactors at the Heysham-1 power station south of Morecombe have also been shut down.
A British Energy spokesperson said: "As this issue may have implications for sister units at Hartlepool and Heysham 1, British Energy has taken a conservative decision to take two of these units out of service for assessment and inspection."
Meanwhile, Torness power station in East Lothian was closed down on Friday after an electrical fault was discovered.
Analysts feared that the plants could remain closed for several months, causing a surge in UK energy prices.
British Energy said: "We are currently assessing our return to service dates for these units.
"In determining these dates, British Energy will consider the potential to integrate any additional inspection work arising from our assessment within planned outages over the balance of the year. The company will give a further update in due course."
The shut downs follow the four month closures of reactors at Hinkley Point B and Hunterston B power stations last year after cracks in boiler tubes were discovered. The plants are now only back up to 60 per cent operating capacity.
Nearly £500 million was wiped from the value of British Energy shares since the closure amid fears that the group will now miss full-year output targets.
Industry figures said that despite tight supplies, there should be more than enough spare capacity across the UK to cope with winter peak demand. However, the National Grid is reported to have asked power companies across the country to increase output for the first time in 18 months.