By Kevin Lynch
Nuclear power plants around the world were on red alert today amid fears that they could be the next targets of a terrorist attack.
The move follows warnings by the International Atomic Energy Agency that a nuclear attack by terrorists is "far more likely" now than it was before the September 11 attacks.
Experts from around the world have been meeting at the IAEA in Vienna to discuss nuclear terrorism and call for a review of nuclear safety at facilities worldwide.
They say governments have to recognise the safety and security of nuclear material is a global concern.
The agency said it would need at least an extra £36 million a year to strengthen and expand its programmes to meet the terrorist threat.
Nuclear facilities are designed to withstand earthquakes, tornadoes and accidental crashes of small aircraft, but not acts of war.
The extent of damage caused by a fully-fuelled jetliner crashing into a facility such as the nuclear reprocessing plant at Sellafield in Cumbria, is still largely unknown.
Scientists estimate that 25 kilos of highly-enriched uranium and eight kilograms of plutonium would be needed to make a nuclear bomb. But scientific expertise and sophisticated equipment would also be needed.
Ed Lyman, scientific director for the Nuclear Control Institute, told the BBC nuclear power plants in the US would be vulnerable to the kind of attacks on the World Trade Centre and the Pentagon.
"They were not designed with this kind of attack in mind, and it is foolish to make statements, like some in the industry have, that plants could withstand that," Mr Lyman said.
"The kind of missile generated by the engine of a large aircraft could penetrate several feet of steel-reinforced concrete."
But Steve Kerekes, spokesman for the Nuclear Energy Institute which represents the nuclear power industry, said four feet of steel-reinforced concrete is only one of the external barriers protecting nuclear reactors.
The steel-reinforced concrete is then lined with an inch of steel, and the reactor vessel is made of six inches of steel, he said. The fuel is encased in zirconium alloy rods. US nuclear power plants are designed to withstand earthquakes, hurricanes and flying debris from hurricanes, he said.