cores of up to 14 UK reactors, rendering them at increased risk of a radiological accident.

In a report prepared for the environmental group Greenpeace, which has long been a critic of the continued use of nuclear energy, nuclear expert John Large called the cracked graphite cores "a central nuclear safety component."

Large became famous in 2000 for helping the Russian Federation rescue the nuclear powered submarine, Kursk, after it sunk in the Barents Sea.

"The core serves to moderate (slow) the neutrons initiating fission in the nuclear fuel," he explained. "Within it are formed about 330 vertical channels that receive stringers of nuclear fuel, it provides for the high pressure flow of the carbon dioxide gas coolant and, importantly, vertical interstitial channels for the entry of control and shut down rods and, if needed, the secondary and emergency reactor close down systems. For nuclear safety it is absolutely essential that the vertical fuel and interstitial channels remain closely aligned during normal service operation and fault conditions under which abnormal forces may arise across the core assembly overall and within the individual graphite bricks."

Nuclear authorities in Britain reacted with calm, however. Representatives of British Energy told the BBC the damage was "known about, anticipated for, within the safety case."

In general, one official said, "cracks will occur in some of the bricks as part of the normal aging process within the graphite reactor core."

But inspectors quoted in the internal documents seem to tell another story.

"There is significant uncertainty in the likelihood and consequences for core safety functionality posed by graphite component and core damage," the documents read.

The UK government is expected to publish the long-awaited results of its so-called "Energy Review" on Tuesday, which will set the course for the development of the country's energy sector. The recommendations are expected to include a renewed focus on nuclear power.

Greenpeace Executive Director Stephen Tindale expressed outraged after releasing the government files. "These documents don't just show the structural damage to nuclear reactors in the UK," he said. "They show the incompetence of the government and British Energy, who have known about these significant cracks yet have refused to do anything about it."

Regardless, almost all scientists agree that the risk of a nuclear disaster are increasing annually as reactors--most of which came on line in the 1970s--pass their 20th and 30th birthdays.

"The risks of a catastrophe change as nuclear reactors change, much like the risks for accident or illness change as people get older," explains Dave Lochbaum, Director of the Nuclear Safety Project at the Union of Concerned Scientists in Washington, DC.

Already, there have been a number of "near-misses" involving American nuclear plants, Lochbaum says, including radioactive releases at Indian Point Unit 2 in New York, cracking in the nozzles at Oconee Unit 3 in South Carolina, and the failure of jet pumps at Quad Cities Unit 1 in Illinois.

The Connecticut Yankee nuclear power plant is currently being demolished because of multiple leaks. The Troy nuclear power plant in Oregon shut down twenty years early, after a cracked steam tube released radioactive gas into the plant, in 1992.

Lochbaum says the flow of information on nuclear safety in the U.S. is better than in Britain, though, since all government reports are easily viewable on the Nuclear Regulatory Commission's (NRC) Web site. The problem, he says, is that Congress has cut the NRC's budget, leading to a 20 percent reduction in safety inspections.

According to the private firm Good Night Consulting, corporate-sponsored safety inspections are also down, meaning that as nuclear plants get older and more accident prone, they're being inspected less and less.

"Aging reactors with less monitoring is a dangerous combination," Lochbaum says dryly.