Some might call it the "doomsday scenario" and, with little need for overstatement, the director of the International Atomic Energy Agency, Mr Mohamed El Baradei, said yesterday the prospect of nuclear terrorism had been "catapulted to the forefront" of public consciousness since the September 11th terrorist attacks on the US.
The new terrorist threat to nuclear installations presented by hijacked aircraft, highlighted by the agency during a four-day conference in Vienna this week, is no doubt concentrating minds at the Office for Civil Nuclear Security, which regulates security procedures at nuclear sites in Britain.
There are 33 operational reactors in Britain providing about 26 per cent of the nation's electricity. Most sites have two nuclear reactors but some, including Calderhall in Cumbria and Chapelcross in Scotland, have four reactors each. There are 12 installations relatively close to Ireland's east coast, such as Wylfa on Anglesey, Sellafield in Cumbria and Trawsfynydd, north Wales, which is undergoing decommissioning but has radioactive material in its reactor hulk.
Long-standing safety arrangements at nuclear installations include air exclusion zones around all sites extending in some cases up to two miles and reinforced concrete walls to protect reactors.
Armed guards are posted at several nuclear installations and all nuclear operators must have site security and transport plans in place and must liaise with local authorities and the police to meet statutory requirements to guard against accidents, theft of nuclear material and sabotage.
Security at nuclear installations is "very stringent" and "kept constantly under review", according to the Department of Trade and Industry, which is the lead British government department for co-ordinating nuclear policy in England and Wales.
However, mindful of exaggerating the threat of nuclear terrorism and giving away any advantage to terrorists, the government has refused to discuss the detail of contingency plans and security arrangements.
The security services and the government have advised there is no specific terrorist threat against Britain. However, a general uncertainty about the nuclear industry and recent warnings about the vulnerability of some European nuclear installations has led Greenpeace UK to question whether Britain is ready to deal with determined terrorists.
"The plans are certainly inadequate and don't make the sites safe," argues Mr Mark Johnson, spokesman for Greenpeace UK, who says even if missiles were placed next to nuclear sites, the speed of an aircraft would make it impossible to launch them in time.
"A high-speed airliner flying through an exclusion zone only requires about 20 seconds flying time to reach a nuclear installation. It is almost impossible that an effective defence could be mounted."
Whether the missiles now stationed outside the Cap de la Hague nuclear site in France could deter a terrorist attack is unclear. In Britain, the public has been assured that security is "constantly under review" and as recent events at Sellafield demonstrated, the RAF is ready to respond to security alerts in the skies over Cumbria.
But in these uncertain times, many are asking, is that enough?