British Energy has warned that profits will take a knock after problems at four of its nuclear reactors.
British Energy is braced for a tough second half of the financial year
The UK's biggest power provider posted a small increase in half-year earnings but was downbeat on the outlook for the second half of the financial year.
Shares in British Energy have slid in recent weeks as the company was forced to shut down four reactors after problems with boiler closure units.
The firm reported a 6% rise in underlying earnings to £511m.
Last month, the firm took two reactors at Hartlepool and two at Heysham out of service following a routine inspection that revealed the problems with the boiler units.
Electricity output from the group's fleet of eight nuclear reactors was hit in the first half by the need to run its Hinkley Point B and Hunterston B units at reduced power after fixing boiler cracks there.
British Energy Group is the UK's largest producer of electricity. It operates eight nuclear power stations and one coal-fired power station.