A London court last Tuesday learned just how simple it might be to bring a form of nuclear terrorism to a major city. All a terrorist would need, the court was told, is a so-called "dirty bomb" assembled from household smoke detectors.
Most smoke detectors that trigger an alarm contain a small quantity of the radioactive isotope, Americium- 241, a by-product of the plutonium- 241 generated in nuclear reactors.
In almost all circumstances, household smoke detectors present no risk to occupants, according to the Melbourne Uranium Information Centre, a service funded by the uranium industry. But Americium- 241, says the centre's website, can be "a potentially dangerous isotope if it is taken into the body in soluble form".
Dhiren Barot, 34, an al-Qaeda- linked would-be terrorist whom the court sentenced to life imprisonment, had a plan to arrange just that in New York and London. He sought al-Qaeda funds to buy 10,000 smoke detectors containing radioactive material at 5 ($A12.40) each, and either "set them alight" or "place them on top of an explosive device". The immediate death toll might be small or nonexistent, but the ensuing panic might well empty most of a city.
"Dirty bombs" scientists call them radiological dispersion devices are, of course, the least of the world's radioactivity fears. A terrorist nuclear bomb of the kind that devastated Hiroshima and Nagasaki tops the list of 21st century worries.
That fastest measure of what the world is thinking about the Google Search website returns 17.1 million listings for "nuclear terrorism".
Hollywood, of course, caters to the fear. For the past couple of movie decades, wild-eyed gentlemen with nuclear backpacks have been threatening the central business districts of major cities.
Exploded in New York's Times Square on a week day, a 10-kiloton bomb, one even smaller than Hiroshima's, would vaporise everything between Carnegie Hall and the Empire State Building, we're told, destroy the United Nations headquarters and kill an estimated 500,000 people. One such bomb detonated at, say, Parliament House, would effectively obliterate the ACT.
Washington's ever-booming rent- a-threat industry makes the most of the angst generated by such notions.
As The Bulletin of Atomic Scientists recently put it, "Sometimes it seems as if the sources of newly announced dangers must be the basement of the White House or a back room at a Washington think tank, where the thousands of monkeys who have yet to type out exact copies of Shakespeare's works are nonetheless producing dozens of new ideas for attacks on America, to be trotted out on the news at 10."
What really are the odds of an attack by a terrorist's nuke (something way above RDD level)?
Probably quite low, says the most recent authoritative study of the problem.
A paper released by London's International Institute for Strategic Studies takes the view that "the risk of nuclear terrorism, especially true nuclear terrorism, employing bombs powered by nuclear fission, is overstated, and that popular wisdom on the topic is significantly flawed".
The paper Nuclear Terrorism After 9/11 (IISS Adelphi series, 378), by Robin M.Frost, a Canadian government analyst specialising in nuclear proliferation looks at "the considerable, probably insurmountable, technical challenges" in obtaining a nuclear weapon "whether 'home-made' or begged, borrowed or stolen from a state arsenal".
Especially since the Soviet Union's collapse in 1992, the stolen weapon has received much attention. During a series of interviews that I made for Fortune magazine in Siberia in 1998, Russia's former national security adviser, General Aleksandr Lebed, told me that more than 100 suitcase- sized nuclear bombs had gone missing during the Soviet break-up.
(Earlier, he had told a US congressional delegation that 84 such weapons were unaccounted for.) Others were doubtful that the Soviet arsenal had such weapons. At the time, the general (who subsequently died in a helicopter crash) was a provincial governor preparing to run for the Russian presidency and was not averse to seeking headlines. I decided not to use the information in the profile of him that I wrote for Fortune.
However, eight years later, Google websites are still quoting what is probably Lebed's misinformation.
Despite endless reports and speculation, concludes Frost, "no one has been able to provide, at least in the open sources, concrete evidence of a single case in which a substantial portion of the fissile materials needed to make a bomb had been, or was close to being, illicitly transferred to terrorists, organised criminals or, indeed, anyone actively seeking them".
So perhaps a terrorist group could find the scientists and funding and make their own bomb? Again, highly improbable, says Frost.
The hurdles would be daunting.
The simplest known bomb project - South Africa's six-nuke arsenal - required $US1billion (1980s purchasing power) and 400 people working from the early 1960s to 1982.
In utter secrecy, the terrorists would have to acquire, inter alia, the technicians; precision-calibrated, computer-guided machine tools; weaponised fissile material (either 25kg of highly enriched uranium or 8kg of plutonium); at least 50kg of high explosives; and a supply of kryton switches (for a bomb's detonating circuitry).
Plutonium has bizarre physical properties - six different crystalline forms as it moves from room temperature to a molten state. The technicians would be in serious danger of radiation-induced cancer or, because of its tendency to burst into flames, of being burned alive.
The Rocky Flats weapons core production centre near Denver, Colorado, is known to have had 31 plutonium fires between 1966 and 1969 alone.
Production of a portable device by terrorists struggling with all these hazards is the unlikeliest development of all. The smallest nuclear weapon known to have been built by the US was a plutonium device measuring 26.4cm by 38.5cm and weighing around 22.8kg. Yield was proportionately low: between 0.01 and 0.25 kilotons (at most, 140th the force of the Hiroshima bomb).
Miniaturisation of this nature would greatly complicate development. South Africa's bare- bones nukes identified by the IISS paper as a possible template for a non-state terrorist group's nuclear effort weighed about one metric ton and had a diameter of nearly 65cm and length of about 1.8m.
Frost feels that though the chance of such small terrorist groups as Al- Qaeda acquiring true nuclear weapons "is extremely unlikely", the "risks of their using RDDs could be high".
Such relatively minor weapons of mass destruction would be "unlikely to kill anyone immediately, except via the direct effects of the conventional explosives involved".
But fear of a slow death from cancer could quickly demoralise, and possibly empty, a city.
In analyst Frost's view, however, and despite terrorist Barot's plot, there aren't likely to be too many backyard bomb makers.
Frosts's paper concludes: "Terrorists in general probably share the same ignorance and fear of WMD prevalent in the broader population, and probably see little reason to turn to unknown, possibly unpredictable and certainly dangerous substances or so, at least, we hope."
An optimistic note?
I'd be more comfortable if his optimism were a little less guarded.
Anthony Paul is a former editor-at-large Asia/Pacific for Fortune magazine, now based in Brisbane.