Radioactive Litvinenko poison trails now much easier to detect

Bouncing-bomb lab unveils cunning long-range Geiger counter

Topflight British government boffins say they have at last cracked the knotty problem of cleanup following Alexander Litvinenko style radioactive-poison murders or similar incidents in which radiological contaminants are spread about the place.

In the case of Litvinenko, the dying Russian - having been poisoned with the isotope polonium-210 by sinister forces whose identity is easy to guess but hard to prove - travelled here and there leaving radioactive pollution in his wake. Almost 50 different premises in London had to be checked out using specialist personnel and equipment, costing the Health Protection Agency some £2 million.

The expense and difficulty was due to the fact that the contaminants resulting from polonium-210 poisoning emit alpha radiation. Alpha particles - each made up of two protons and two neutrons - generally travel no more than 2cm through the air before reacting with something and so disappearing, which makes them hard to detect using conventional scintillation and Geiger counters. The instruments must be carefully swept very close to every surface to detect any contamination.

But now, boffins at the National Physical Laboratory (NPL) have come up with a better solution. When alpha particles are emitted into air, one of the likelier things that can happen to them is that they will hit a nitrogen molecule and ionise the nitrogen. This event causes a distinctive ultraviolet fluorescence, which the NPL scientists have now developed means to detect using an optical instrument.

Ultraviolet rays travel happily through air, glass etc, meaning that the snail-trail left by any future radioactive poisoning victims could potentially be detected from kilometres away rather than centimetres - though the NPL inventors caution that the optics for such long-range instruments would be "non portable". For now, their portable prototype instrument reliably detects alpha-emitting substances from 20cm - 10 times the distance achievable with ordinary Geiger counters. The new gizmo, based on custom electronics and swappable 1-inch optics, can apparently run for eight hours on a li-ion battery.

There is one caveat, however: there are many other sources of UV apart from alpha-particle ionisation, so the NPL boffins caution that rooms to be scanned using the new instrument need to be illuminated with sodium lamps only.

"The filtered detector is entirely blind to the wavelength of light emitted by sodium lights," says an NPL statement released yesterday.

"By producing a prototype that can measure radiation up to 10 times further away than current methods, we can greatly improve the time it takes to safely assess any suspected radioactive areas," says the NPL's Ray Chegwin. "Our prototype could have saved the time it took to monitor the areas relevant to the Litvinenko case, and cut the costs of such an essential operation. Of course, the detector could be used to support radiation safety and decommissioning operations in the nuclear industry, among others, and we're currently investigating these." ®

Bootnote

Other noted inventions in which the NPL have had a hand include the WWII "bouncing bomb" of Dambusters fame, the robotic cauliflower harvester and of course the actual internet.

According to the NPL (pdf page 12): "The first practical networks using packet switching were introduced to the NPL local network, and by the early 1970s this was providing a range of on-line services to some 200 users. This demonstration provided a much needed steer to the development of the [US] Arpanet, which would evolve into the Internet we know today." ®

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