One of the problems with radioactive contamination is that it is invisible. Smoke blackens, oil stains, chemicals discolour, but you can鈥檛 actually see dangerous ionising radiation with the naked eye.
But now a British company is working on a system that shows up radioactivity as a glow in the dark. With a pair of modified military night-vision goggles, scientists monitoring radioactive contamination at the scene of a possible spill would be able to spot smears of alpha-emitting radionuclides such as plutonium.
The radiation goggles designed by British Instrument Consultants (BIC) in Warrington, Cheshire, are based on an old technique. Early last century, nuclear pioneer Ernest Rutherford saw the flashes of light given off by zinc sulphide when it is struck by alpha particles. The effect, known as scintillation, is commonly used in radiation monitors which convert the flashes of light into electronic signals.
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BIC wanted to find a way of boosting the weak flashes given off by low levels of radioactivity until they鈥檙e visible to the human eye. To do this, the company took a pair of night-vision goggles and tuned them to highlight light wavelengths emitted by scintillating zinc sulphide.
The result, according to BIC spokesman Mike Scott, is that you can see alpha contamination as low as 30 becquerels per square centimetre as an intense glow on the goggles鈥� green monochrome screen. 鈥淭he main advantage is being able to measure contamination of unusually shaped objects,鈥� he says. 鈥淲ith standard probes it鈥檚 very difficult to get into nooks and crannies.鈥�
The goggles, which have been tested at the University of Liverpool, would also enable staff monitoring an area to keep well away from contamination. One disadvantage, though, is that you have to spray zinc sulphide onto the area under investigation.
Furthermore, you can only use the goggles out of doors at night because daylight swamps the sensitive electronics, though filters might make it possible to see the glow in ambient light, Scott says.
Nevertheless, Scott says some of the major players in the nuclear industry, including the UK Atomic Energy Authority (UKAEA) and British Nuclear Fuels (BNFL) have already expressed an interest.
The goggles could be useful in identifying hot spots of plutonium contamination at the nuclear plants being decommissioned at Dounreay in Caithness and Sellafield in Cumbria, he argues.
Scott, a physicist who has specialised in radiation measurement, accepts some people would prefer a device that could detect lower levels of contamination and other forms of radioactivity.
But he is confident that he can improve his design to highlight contamination down to 10 becquerels per square centimetre. He is also planning to investigate other materials such as plastics that are susceptible to scintillation from beta, neutron and gamma radiation.
Peter Burgess from Britain鈥檚 National Radiological Protection Board says that while BIC鈥檚 idea is a clever notion, he is worried that spraying potentially contaminated areas with zinc sulphide might send radioactive particles into the air and worsen the clean-up problem.
But the UKAEA believes the technology 鈥渟ounds very interesting鈥� and could be useful. 鈥淏ut we need to reserve judgement until we have seen it demonstrated,鈥� a spokesman says. BNFL takes a similar tack, arguing that the goggles are the 鈥渟park of an idea鈥� that needs more work and testing before they would be willing to use them.