THE bill for cleaning up atomic waste has soared by GBP 2 billion to GBP 65 billion, with the watchdog set up to deal with Britain's nuclear legacy warning that costs could rise further.

Estimates of the long-term costs of radioactive waste disposal were unveiled by the Nuclear Decommissioning Authority (NDA), set up in April 2005 to oversee the dismantling of Britain's ageing nuclear power stations.

Most of the increased costs were attributed to the huge clean-up of the Sellafield nuclear reprocessing plant.

But the NDA also warned that plans from contractors had weaknesses that could lead to "substantial" changes in costs.

"Our sites do not currently assess risk and allocate contingency on a consistent basis," the NDA said in its first annual report. "These weaknesses could lead to substantial amendments in costs and schedule of work."

The authority revealed that it would fine Sellafield's Thorp plant and Dounreay in Caithness GBP 2 million each for recent radioactive leaks.

Thorp may not reopen until 2007 because of the leak in April 2005, while radioactive material also escaped into a sealed cell in Dounreay in June this year.

"We have reminded our contractors that we will not tolerate such incidents," the NDA said.

"The latest version of our lifetime plans - which detail the commercial operations, decommissioning and clean-up programmes of our 20 sites - show a total cost of GBP 64.8 billion, a net increase of GBP 2.1 billion."

Dr Ian Roxburgh, the NDA's chief executive, also warned that more needed to be done to reduce hazards around its sites, particularly immobilising "large quantities of stored intermediate-level waste".

Duncan McLaren, Friends of the Earth Scotland's chief executive, said the nuclear waste clean-up bill would keep rising.

"These figures don't even include all the radioactive waste we know about, or the waste still to be produced. Add to this the cost of the government's proposed multi-billion pound nuclear dump and you start to question the motives behind those who would have us build a new generation of nuclear power plants," he said.

In its report, the NDA also said its goal was to "encourage our contractors to perform more work for less money". It will take over the work of radio active waste management company Nirex in finding suitable sites for deep storage of nuclear material. But this move drew criticism from politicians and unions.

Chris Huhne, the Liberal Democrat environment spokesman, said: "There is now a conflict of interest at the heart of nuclear safety."

Prospect, the union that represents Nirex workers, also wrote to David Miliband, the Environment Secretary, saying it was "astounded and annoyed" that its years of work had been ignored.

HUNTERSTON CRACKS 'A THREAT TO SAFETY'

IMMINENT cracking in the Hunterston nuclear station will affect its ability to operate safely, the Nuclear Installations Inspectorate has warned.

Its assessment of the Ayrshire plant and its twin, the Hinkley Point station, raised concerns about the safe running of Britain's ageing nuclear reactors.

Just one of British Energy's eight nuclear stations was fully operational last week.

"The majority of fuel moderator bricks will develop a single through-thickness crack," the inspectorate's report said.

Further cracks could split the bricks in half.

"Brick cracking could affect the ability of the graphite core to meet its safety requirements," it added.

It could take up to six months to fix existing cracks in the boiler tubes at Hinkley, which were disclosed last week by British Energy.

Both stations, which provide 6 per cent of Britain's electricity, have been closed, but the industry and the government want their 30- year lifespans extended by a decade.

They account for around a fifth of British Energy's income, or GBP 2 million a week.

The company said the problem was "solvable".