ESTIMATED cost of decommissioning the Capenhurst nuclear site has almost doubled in the past couple of years.

The Nuclear Decommissioning Agency (NDA) is currently involved in a major project to clean up the former BNFL fuel enrichment facility.

In 2005/06 the estimated cost of the work was £596m. But an NDA spokeswoman said this had now risen to £958m.

The revelation came in the wake of a report from spending watchdog the National Audit Office (NAO) which said the cost of taking out of service ageing nuclear power sites has risen “rapidly” in the past few years by £12bn to £73bn.

Sir John Bourn, head of the NAO, said while there was a better idea about “the scale of the task”, the “estimates of costs to the taxpayer had continued to rise”.

Environmental campaigners said the Government should heed the warnings of the NAO report.

Nathan Argent, nuclear campaigner for Greenpeace, said: “That we can’t properly estimate the cost of dealing with our legacy wastes, let alone resolve what to do with them, underscores the fact that plans to build a second generation of new reactors are pure recklessness.”

In a statement the NDA said that in less that three years since its creation the authority had gained a “detailed understanding” of the sites.

Dealing specifically with Capenhurst, a spokeswoman said: “Our current life-time plan for the Capenhurst site estimates the total cost of decommissioning to be around £958m.

“We revise our costs estimates every year as we continue to move from a position of uncertainty about the exact nature of work that needs to be done – to one which provides a firm basis for the work to be fully scoped and costs to be estimated.

“As we gain this better understanding of the risks that need to be handled we’ve had to manage our contingency plans accordingly.”

She added: “The estimated figure in 2005/06 for the overall cost of decommissioning at Capenhurst was £596m. However, the costs of the clean-up programme were always expected to rise in the early years of our evolution as we and our sites formed a greater understanding and more realistic assessment of the task ahead.

“The ‘End of Decommissioning’ milestone at Capenhurst is scheduled to be achieved in 2010. From this date the main activities on site will be the ongoing storage and maintenance of NDA assets.”