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[cdn-nucl-l] A new means for "seeing" radiation
From New Scientist http://www.newscientist.com/tech/glowforit.jsp
Glow for it
Wear these goggles and see radioactivity with your own eyes
ONE OF the problems with radioactive contamination is that it is invisible.
Smoke blackens, oil stains, chemicals discolour, but you can't 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.
BIC wanted to find a way of boosting the weak flashes given off by low
levels of radioactivity until they're 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' green monochrome screen. "The main advantage is being
able to measure contamination of unusually shaped objects," he says. "With
standard probes it's very difficult to get into nooks and crannies."
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. And 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
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
Peter Burgess from Britain's National Radiological Protection Board says
that while BIC's 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 "sounds very interesting" and could be useful. "But
we need to reserve judgement until we have seen it demonstrated," a
spokesman says. BNFL takes a similar tack, arguing that the goggles are the
"spark of an idea" that needs more work and testing before they would be
willing to use them.
Rob Edwards, Edinburgh
17 March 2001