Sydney: Mining giant Rio Tinto apologised Monday for losing a tiny but dangerously radioactive capsule that fell off a truck along a 1,400-kilometre-long stretch of road in Western Australia.
The solid, silver-coloured cylinder is smaller than a human fingernail - just 8mm by 6mm - but the authorities say it contains enough Caesium-137 to cause acute radiation sickness.
It disappeared this month from a truck that drove to the suburbs of Perth from a remote mine near the town of Newman, which lies 1,400 kilometres (870 miles) north of the state capital - further than the distance from Paris to Madrid.
"We recognise this is clearly very concerning and are sorry for the alarm it has caused in the Western Australian community," said Rio Tinto Iron Ore chief executive Simon Trott in a statement sent to AFP.
"We have launched our own investigation to understand how the capsule was lost in transit," he added.
The radioactive capsule, part of a gauge used in the mining industry to measure the density of iron ore, was transported by a certified Rio Tinto contractor, he said.
People should stay at least five metres (16 feet) away from the capsule, which emits beta and gamma rays with a radiation level equivalent to receiving 10 X-Rays every hour, the authorities have warned.
"If you have it long enough near you, it could cause what is known as acute radiation sickness," Western Australia's chief health officer Andrew Robertson said when the public were first alerted on Friday.
The container it was in collapsed because of the vibrations of the road trip, he said. The capsule apparently fell through the hole left by a bolt that was also lost.
The gauge was originally picked up on January 12 from the Gudai-Darri iron ore mine near Newman and delivered to the Perth suburb of Malaga on January 16, Rio Tinto says.
But the package was not opened until January 25 when the gauge was found "broken apart" with the radioactive capsule missing. State police were informed on the same day.
Officials in high-visibility yellow vests were seen walking along key stretches of the road - such as where the truck had stopped - but the capsule remains missing.
Portable radiation monitors that can be mounted on vehicles are being used to detect emissions across a 20-metre radius along the route, Western Australia's emergency services said.
"We are not trying to find the small capsule by eyesight. The radiation equipment will hopefully lead us to it," said a statement by the service's incident controller, acting superintendent Darryl Ray.
Finding the capsule will not be easy, said Dale Bailey, professor of medical imaging at the University of Sydney and Royal North Shore Hospital.
"Given the large distance involved it will be akin to finding a needle in a haystack," Bailey said.
"Radiation detectors on moving vehicles can be used to detect radiation above the natural levels but the relatively low amount of radiation in the source means that they would have to sweep the area relatively slowly."
Rio Tinto's public image took a hit in an unrelated incident in 2020 when it blew up the 46,000-year-old Juukan Gorge rock shelters in Western Australia, sparking a scathing parliamentary inquiry and promised reforms.