Rio Tinto apologises for loss of tiny radioactive capsule in Australian outback

© Reuters. FILE PHOTO: The Rio Tinto logo is displayed on a visitor's helmet at a borates mine in Boron, California, U.S., November 15, 2019. REUTERS/Patrick T. Fallon/File Photo

MELBOURNE (Reuters) - Rio Tinto (LON:RIO) Ltd apologised on Monday for the loss of a tiny radioactive capsule that has sparked a radiation alert across parts of the vast state of Western Australia.

The radioactive capsule, believed to have fallen from a truck, was part of a gauge used to measure the density of iron ore feed which had been entrusted to a specialist contractor to transport. The loss may have occurred up to two weeks ago.

Authorities are now grappling with the daunting task of searching along the truck's 1,400 kilometre (870 mile) journey from north of Newman - a small town in the remote Kimberley region - to a storage facility in the northeast suburbs of Perth - a distance longer than the length of Great Britain.

The task, while akin to finding the proverbial needle in a haystack, is "not impossible" as searchers are equipped with radiation detectors, said Andrew Stuchbery who runs the department of Nuclear Physics & Accelerator Applications at the Australian National University.

"That's like if you dangled a magnet over a haystack, it's going to give you more of a chance," he said.

"If the source just happened to be lying in the middle of the road you might get lucky...It's quite radioactive so if you get close to it, it will stick out," he said.

The gauge was picked up from Rio's Gudai-Darri mine site on Jan. 12. When it was unpacked for inspection on Jan. 25, the gauge was found broken apart, with one of four mounting bolts missing and screws from the gauge also gone.

Authorities suspect vibrations from the truck caused the screws and the bolt to come loose, and the radioactive capsule from the gauge fell out of the package and then out of a gap in the truck.

"We are taking this incident very seriously. We recognise this is clearly very concerning and are sorry for the alarm it has caused in the Western Australian community," Simon Trott, Rio's iron ore division chief, said in a statement.

The silver capsule, 6 millimetres (mm) in diameter and 8 mm long, contains Caesium-137 which emits radiation equal to 10 X-rays per hour.

Authorities have recommended people stay at least five metres (16.5 feet) away as exposure could cause radiation burns or radiation sickness, though they add that the risk to the general community is relatively low.

"From what I have read, if you drive past it, the risk is equivalent to an X-ray. But if you stand next to it or you handle it, it could be very dangerous," said Stuchbery.

The state's emergency services department has established a hazard management team and has brought in specialised equipment that includes portable radiation survey meters to detect radiation levels across a 20-metre radius and which can be used from moving vehicles.

Trott said Rio had engaged a third-party contractor, with appropriate expertise and certification, to safely package and transport the gauge.

"We have completed radiological surveys of all areas on site where the device had been, and surveyed roads within the mine site as well as the access road leading away from the Gudai-Darri mine site," he said, adding that Rio was also conducting its own investigation into how the loss occurred.

Analysts said that the transport of dangerous goods to and from mine sites was routine, adding that such incidents have been extremely rare and did not reflect poor safety standards on Rio's part.

The incident is another headache for the mining giant following its 2020 destruction of two ancient and sacred rock shelters in the Pilbara region of Western Australia for an iron ore mine.