THE cost of decommissioning and demolishing the Sizewell A nuclear power station is officially estimated to be £870 million, it has been disclosed.However, the estimate is based on the work taking more than 100 years and the Nuclear Decommissioning Agency (NDA), the state agency which now owns the power station, said yesterday the figure could go up or down.

The £870 million needed to decommission and demolish Sizewell A will partly be spent on the work of specialist contractors who will dismantle radioactively contaminated plant and buildings and, ultimately, the highly radioactive cores of the two gas-cooled reactors.

Other sums will go on the packaging and transport of radioactive waste.

Half of the money is expected to come from the Treasury and half from commercial activity on the UK's nuclear sites, all of which - except Sizewell B - are now owned by the NDA.

According to the NDA, the cost of decommissioning and clearing the sites of all of the UK's nuclear installations will be £56 billion .

About 60% of this will be needed to clean-up the Sellafield nuclear reprocessing site in Cumbria.

Formerly known as Windscale, this site is heavily contaminated by radioactivity and provides the current store for the national stockpile of plutonium, a dangerous material which is extracted from spent nuclear fuel and is subject to tight security.

Other large sums will go on the decommissioning of sites which produce nuclear fuel or provide nuclear research and development facilities and the rest will be spent on clearing the nuclear power station sites.

Brian Hough, NDA spokesman, said: “The current estimate for Sizewell A is £870.6 million but this could change according to a range of factors.”

Mary Edwards, East Anglian spokeswoman for Friends of the Earth, said: “The economics of nuclear power only add up in the world of Alice in Wonderland.”

She said a new round of nuclear power station building would involve huge costs and this was money which could be spent on creating a sustainable energy future - through renewable forms of electricity generation.

“Nuclear is a vast red herring that will take money away from innovation and take us back to the Dark Ages,” she added.

Charles Barnett, chairman of the Shut Down Sizewell Campaign, said the figure for decommissioning was based on the belief that capital invested now would make interest and finally produce the sum required.

However, economics over a period of 100 years were uncertain and the taxpayer could have to hand out further sums on top of the estimate.

“We don't know what is going to happen to the economy or interest rates. There is no guarantee the money will materialise,”

Mr Barnett said.