A NUCLEAR safety watchdog may force Sizewell B to shut down for up to ten weeks – potentially costing troubled British Energy more than £20million, it emerged last night .

By David Green

A NUCLEAR safety watchdog may force Sizewell B to shut down for up to ten weeks – potentially costing troubled British Energy more than £20million, it emerged last night .

Routine checks have uncovered two "suspect" welds in part of the reactor's cooling system, and further tests are being carried out this week to establish if there is a problem.

Cash-strapped British Energy admitted last night its flagship reactor may be out of action for up to ten weeks if work is needed – costing it an estimated £300,000 to £400,000 every day of any shut down.

The company was only recently saved from liquidation following the last-minute negotiation of a £1.3 billion deal with the Government. Electricity wholesale prices have also surged following the news.

John McNamara, Sizewell B spokesman, said there had been two "anomalies" in the weld test results and these were being investigated. Other types of test on the same welds had failed to identify any problem.

"We are likely to know within the next couple of days whether we are going to have to carry out work on the welds and this could take between two and ten weeks.

"Until we satisfy the Nuclear Installations Inspectorate we cannot restart the reactor," he said.

Potential problems with two of 180 pipe welds in the Sizewell B reactor's secondary cooling circuit have been detected during the regular four to five week shutdown - carried out every 18 months - for maintenance and safety checks.

A series of tests were carried out on each of the welds and one resulted in two of the welds coming under suspicion of having cracks.

Further tests are being carried out to check the findings and an announcement is expected early this week following consultations with the NII, the UK nuclear safety watchdog.

However, any lengthy closure of Sizewell B, which employs about 350 people and generates 1,187 megawatts of electricity into the national grid system, could financially unbalance British Energy once more.

It is estimated loss of electricity sales from the power station over a ten-week period would cost it more than £20 million.

John Large, a London-based independent nuclear safety consultant, said last night that any weld cracks in Sizewell B would be different from the cracks which caused a 12-month shutdown of the Wylfa nuclear power station in Wales.

However, he said British Energy could not claim nuclear safety was not a concern because the potential defects had been identified in the secondary circuit - not the primary circuit which cools the reactor.

"If they suddenly lost the secondary circuit there would be nowhere for the cooling water to go and this would be dangerous," he said.

Charles Barnett, chairman of the Shut Down Sizewell Campaign, said: "If there is any possibility of a problem it is the duty of the NII to withhold permission to restart the reactor."