PROBLEMS at the Sizewell B nuclear power plant could see the reactor remain closed until September - potentially costing tens of millions of pounds in lost electricity sales.

PROBLEMS at the Sizewell B nuclear power plant could see the reactor remain closed until September - potentially costing tens of millions of pounds in lost electricity sales.

Sizewell's owner EDF Energy has confirmed that the facility is not expected to be up and running until the third quarter of 2010.

It means the power station, which has been shut since the end of March and employs more than 500 people, could be closed until September while engineers carry out repairs.

Commentators suggest the power station could lose around �350,000 a day in electricity sales.

Working on the basis that it will remain shut until September - about 180 days - it could see losses in the region of �63m.

However, EDF has refused to comment on how much money might be lost in electricity sales because of the commercially sensitive nature of the market in which it operates.

The reactor has been out of service since the end of March following indications of higher-than-normal moisture levels within the containment building. The problem is believed to have been caused by one of the heaters associated with a component known as the 'pressuriser'.

EDF has released a statement saying: 'The scope of the required repair work has now been agreed and will involve removing a number of failed heaters from the pressuriser.

'Two repair techniques are being developed and the timing of the return to service of the station will depend on which technique is eventually chosen to be deployed.

'It is now expected that return to service of this unit will be during the third quarter of 2010, resulting in a total loss in the range 4TWh to 6TWh [terawatts per hour].'

A team of specialists from EDF Energy and contracting partners from Europe and America have been flown in to complete the repair work to the pressuriser.

Using electronic remote equipment, video footage has been taken which enables the company to examine parts of the component in the smallest detail.

Jim Crawford, Sizewell B station director, said: 'Investigative work on the pressuriser has gone well and provided us with valuable information which has helped determine our repair strategy.

'To assist with the repair strategy fuel has been safely removed from the reactor and placed in the fuel storage pond whilst repairs are completed.'

Representatives from the Health and Safety Executive (HSE) and the Environment Agency have said they are satisfied with Sizewell's response to the incident.