British Energy said yesterday that new problems at two of its nuclear reactors would have a significant impact on its full-year results.

Shares slid after the power generator, which has been hit by a series of technical difficulties over the past year, was unable to provide more information about corrosion problems at the Hartlepool and Heysham 1 generators. The shares closed down 12½p, or 2 per cent, at 505p.

Bill Coley, the chief executive, said that although some performance measures were strong across British Energy’s fleet, “it is unfortunate that the output in the second half will be impacted by the boiler closure unit issue at Hartlepool and Heysham 1, which stems from the original design and construction of the stations”.

British Energy’s eight reactors are struggling with corrosion and cracking related to ageing. Hartlepool and Heysham came on stream in 1983. These two, both of which are capable of supplying power to 1.5 million homes, have problems with wiring corrosion in steel and concrete boiler units attached to the reactors. The company may have to spend up to £20 million investigating corrosion in the 54km (33.5 miles) of wire involved in the units.

The problems could force British Energy to buy power on the open market if the reactors remain out of action for the rest of its financial year. Last year British Energy suffered a spate of technical difficulties that left it with only one generator capable of running on full output. The company was forced to buy energy on the market to meet its supply obligations.

British Energy is eager to build nuclear power stations when the Government gives the expected go-ahead for a new nuclear programme. It has spoken to a number of prospective partners for the project, including EDF Energy.

In the six months to September 30, British Energy’s underlying earnings rose to £511 million from £481 million in the same period last year after benefiting from increased power prices. Output fell from 31.9 terawatt hours to 30.7 terawatt hours after continued problems with power stations at Hinkley Point and Hunterston. The two are still working at 60 per cent capacity.

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